# Hopi - full tool reference

> Free online calculators, converters, generators and tools (225 tools). Every tool runs entirely in your browser. This file lists each tool with its description and FAQs so AI systems can understand and cite them. Agent-callable via WebMCP: https://hopi.co.uk/webmcp.json.

## Maths & percentages

### Discount & sale price calculator
https://hopi.co.uk/discount-calculator/

Free discount calculator. Find the sale price and how much you save from a percentage off, a fixed pound amount off, or work out the discount from two prices.

**How do I work out a percentage off a price?** Multiply the original price by the discount as a decimal to get the saving, then subtract it. For 25% off 80 pounds, the saving is 80 x 0.25 = 20 pounds, so the sale price is 60 pounds. A quick check: 25% off leaves you paying 75%, and 80 x 0.75 = 60 pounds.

**Do two discounts add together?** No. Applying 20% off and then a further 10% off is not 30% off. The second discount comes off the already-reduced price, so 100 pounds becomes 80 pounds and then 72 pounds, a total of 28% off, not 30%. Stacked discounts always save a little less than the two percentages added together.

**What does effective discount mean?** It is the single percentage that matches the money you actually saved, useful when the saving is given in pounds or when discounts are stacked. If a 50 pound item is reduced by 15 pounds, the effective discount is 15 divided by 50, which is 30%.

**Is VAT worked out before or after a discount?** For a normal retail price the VAT is already included, so a percentage off the ticket price reduces the VAT in the same proportion. If you are dealing with net (pre-VAT) trade prices, apply the discount to the net figure first, then add VAT. Our VAT calculator handles that step.

**Does the calculator round the sale price?** It shows the exact figure to the penny. Shops sometimes round to a tidy price point such as 59.99, so the till total can differ by a penny or two from the exact maths. The saving and effective discount shown here are the precise values.

### Fraction calculator
https://hopi.co.uk/fraction-calculator/

Free fraction calculator. Add, subtract, multiply or divide two fractions and get a simplified answer, a mixed number and the decimal, instantly.

**How do I add fractions with different denominators?** Rewrite both over a common denominator, then add the numerators. For 1/2 + 3/4, use quarters: 2/4 + 3/4 = 5/4, which is 1 1/4. Cross-multiplying (each top times the other bottom, over the product of the bottoms) does the same job automatically.

**How do I divide one fraction by another?** Flip the second fraction and multiply, sometimes remembered as keep, change, flip. So 3/4 ÷ 2/5 becomes 3/4 × 5/2 = 15/8, which is 1 7/8. Dividing by a fraction smaller than 1 always makes the answer bigger.

**How does the calculator simplify results?** It divides the numerator and denominator by their highest common factor (HCF). For example 2/3 × 3/8 = 6/24, and the HCF of 6 and 24 is 6, so the simplified answer is 1/4.

**What is the difference between an improper fraction and a mixed number?** An improper fraction has a top number bigger than its bottom, such as 5/4. A mixed number writes the same value as a whole number plus a proper fraction, 1 1/4. The calculator shows both forms whenever they differ.

**Can I calculate with negative fractions?** Yes. Put a minus sign in front of either numerator. The calculator keeps the sign on the top of the fraction and handles subtraction that dips below zero, so 1/4 − 1/2 correctly gives −1/4.

### Fraction to decimal converter
https://hopi.co.uk/fraction-to-decimal/

Free fraction to decimal converter. Turn any fraction into a decimal (or any decimal into a simplified fraction) instantly, with recurring decimals explained.

**How do I turn a fraction into a decimal?** Divide the top number by the bottom number. So 3/8 is 3 ÷ 8 = 0.375, and 7/16 is 7 ÷ 16 = 0.4375. Multiply the decimal by 100 if you want it as a percentage.

**How do I turn a decimal into a fraction?** Write the digits after the point over the matching power of ten, then simplify. For example 0.35 is 35/100, and dividing top and bottom by 5 gives 7/20. The converter does the simplifying for you.

**What happens with recurring decimals?** Some fractions never stop, such as 2/3 = 0.6666 recurring, so the tool rounds the decimal to 6 places and tells you it recurs. Going the other way, it finds the closest fraction with a denominator up to 10,000, so typing 0.333333 returns 1/3 rather than an ugly six-figure fraction.

**Which fractions give exact decimals?** A fraction terminates only when its simplified denominator is built purely from the factors 2 and 5. That is why halves, quarters, fifths, eighths and tenths are tidy, while thirds, sixths, sevenths and ninths recur forever.

**How accurate is the decimal to fraction mode?** If your decimal matches a fraction exactly, you get that fraction and it is labelled exact. Otherwise the tool returns the closest fraction it can find with a denominator up to 10,000 and labels it as approximate, showing the decimal it actually equals.

### Mean, median & mode calculator
https://hopi.co.uk/average-calculator/

Free averages calculator. Paste a list of numbers to get the mean, median, mode, sum, count, minimum and maximum instantly. Everything runs in your browser.

**What is the difference between mean, median and mode?** The mean is the total of the values divided by how many there are. The median is the middle value once the list is sorted, or the average of the two middle values if the count is even. The mode is the value that appears most often. Each is a different way of describing a typical value.

**When is the median better than the mean?** When the data is skewed by a few extreme values. Five salaries of 21,000, 24,000, 25,000, 26,000 and 90,000 pounds have a mean of 37,200 pounds, which nobody actually earns, but a median of 25,000 pounds, which is far more typical. That is why house prices and wages are usually reported as medians.

**What if there is no mode?** If every value appears the same number of times, the data has no mode and the tool says so. If two or more values tie for the most appearances, they are all modes and the tool lists each of them. A data set can be bimodal or even multimodal.

**How should I separate the numbers I paste?** Use spaces, commas, semicolons or new lines, in any mixture. One thing to watch: commas are treated as separators, so type 1200 rather than 1,200, otherwise it will be read as the two numbers 1 and 200.

**Is my data uploaded anywhere?** No. All the calculations happen in your browser using JavaScript, so nothing you paste ever leaves your device. You can comfortably paste thousands of values and refreshing the page clears everything.

### Percentage calculator
https://hopi.co.uk/percentage-calculator/

Free percentage calculator. Work out a percentage of a number, what percentage one number is of another, and percentage change. Instant answers as you type.

**How do I work out a percentage of a number?** Divide the percentage by 100, then multiply by the number. For example, 15% of 250 is (15 ÷ 100) × 250 = 37.5. A quick shortcut is to move the decimal point: 10% of 250 is 25, so 15% is 25 plus half of 25, which is 37.5.

**How do I work out what percentage one number is of another?** Divide the first number by the second, then multiply by 100. For example, 30 as a percentage of 120 is (30 ÷ 120) × 100 = 25%.

**What is the difference between percentage change and percentage difference?** Percentage change measures movement from a starting value to an end value, so it has a direction (increase or decrease) and uses the starting value as the base. Percentage difference compares two values with no direction, using the average of the two as the base. Use percentage change for prices over time, and percentage difference for comparing two alternatives.

**How do I add a percentage to a number?** Multiply the number by 1 plus the percentage as a decimal. To add 20% to 80, multiply 80 × 1.20 = 96. To subtract 20%, multiply by 0.80 instead.

**How do I work out percentages without a calculator?** Build from 10% and 1%. To find 10%, move the decimal point one place left. To find 1%, move it two places. Then combine: 23% of 400 is two lots of 10% (80) plus three lots of 1% (12), giving 92.

### Percentage change calculator
https://hopi.co.uk/percentage-change-calculator/

Free percentage change calculator. Enter a starting value and an end value to see the percentage increase or decrease between them, with the working shown.

**How do I calculate percentage change?** Subtract the old value from the new value, divide by the old value, then multiply by 100. From 80 to 100 the change is ((100 − 80) ÷ 80) × 100 = +25%. A positive result is an increase and a negative result is a decrease.

**Why is the old value used as the base?** Percentage change measures movement relative to where you started. Going from 80 to 100 is a 25% increase, but going from 100 to 80 is a 20% decrease. The two directions give different percentages because the starting base is different.

**How do I calculate a percentage decrease?** Use the same formula. If the new value is smaller, the result is negative. From 1,500 to 1,200 the change is ((1,200 − 1,500) ÷ 1,500) × 100 = −20%, a 20% decrease.

**Can percentage change be more than 100%?** Yes, when something more than doubles. From 40 to 100 the change is ((100 − 40) ÷ 40) × 100 = +150%. Decreases, however, cannot go below −100%, which would mean losing more than everything.

**What if the starting value is zero?** Percentage change from zero is mathematically undefined, because you cannot divide by zero. Any growth from nothing is infinite in percentage terms, so state the change in absolute numbers instead.

### Percentage decrease calculator
https://hopi.co.uk/percentage-decrease-calculator/

Free percentage decrease calculator. Reduce any number by any percentage and see the new value and the amount taken off, instantly. Ideal for sale prices.

**How do I decrease a number by a percentage?** Subtract the percentage from 100, turn it into a decimal and multiply once. To decrease 250 by 15%, multiply 250 × 0.85 = 212.5. The multiplier method is quicker and less error-prone than working out the percentage separately and subtracting it.

**How do I work out a sale price?** Multiply the full price by 1 minus the discount as a decimal. 20% off a £64.99 jacket is 64.99 × 0.80 = £51.99, a saving of £13.00. For 30% off, multiply by 0.70 instead.

**How do I reverse a percentage decrease?** Divide by the multiplier rather than adding the percentage back. If a price is £90 after a 25% reduction, the original was 90 ÷ 0.75 = £120. Adding 25% to £90 would give £112.50, which is wrong.

**Can I decrease a number by more than 100%?** You can, but the result goes negative. Decreasing 40 by 150% gives 40 × (1 − 1.5) = −20. For prices and quantities, a decrease of 100% (down to zero) is the practical limit.

**What is the difference between percentage decrease and percentage change?** A percentage decrease applies a known percentage to a starting number to get a new, smaller value. Percentage change works the other way round: you know both values and want the percentage between them. Use our percentage change calculator for that.

### Percentage difference calculator
https://hopi.co.uk/percentage-difference-calculator/

Free percentage difference calculator. Compare two values using the average-based formula and see the symmetric percentage between them, with worked examples.

**What is the formula for percentage difference?** Take the absolute difference between the two values, divide it by their average, then multiply by 100. For 40 and 60 that is 20 ÷ 50 × 100 = 40%. The order of the two values makes no difference to the result.

**What is the difference between percentage difference and percentage change?** Percentage change measures movement from a starting value, so it has a direction: from 40 to 60 is a 50% increase, but from 60 to 40 is a 33.3% decrease. Percentage difference divides by the average instead, giving the same 40% whichever way round you compare. Use change for before and after, difference when neither value is the baseline.

**Why divide by the average?** Because neither value is the original, the fairest yardstick is the midpoint between them. Dividing by the average makes the result symmetric, so comparing a with b gives exactly the same answer as comparing b with a.

**Can percentage difference be more than 100%?** Yes. Comparing 10 and 90 gives a gap of 80 against an average of 50, which is 160%. Any pair of values whose gap is bigger than their average will exceed 100%.

**When should I use percentage difference?** When you are comparing two things side by side and neither is the starting point, such as two quotes, two prices in different shops or two salaries. If one value clearly came first in time, percentage change is usually the better measure.

### Percentage increase calculator
https://hopi.co.uk/percentage-increase-calculator/

Free percentage increase calculator. Increase any number by any percentage and see the new value and the amount added. Ideal for pay rises and price rises.

**How do I increase a number by a percentage?** Multiply the number by 1 plus the percentage as a decimal. To increase 250 by 15%, multiply 250 × 1.15 = 287.5. The multiplier method is quicker and less error-prone than working out the percentage separately and adding it on.

**How do I work out a pay rise?** Multiply your current salary by 1 plus the rise as a decimal. A 6% rise on £32,000 is 32,000 × 1.06 = £33,920. For the monthly difference, divide the increase (£1,920) by 12, which is £160 a month before tax.

**How do I reverse a percentage increase?** Divide by the multiplier rather than subtracting the percentage. If a price is £287.50 after a 15% increase, the original was 287.50 ÷ 1.15 = £250. Subtracting 15% of £287.50 would give the wrong answer.

**Can I increase a number by more than 100%?** Yes. An increase of 150% means the value grows to 2.5 times its original size, because the multiplier is 1 + 1.50 = 2.5. So 40 increased by 150% is 100.

**What is the difference between percentage increase and percentage change?** A percentage increase applies a known percentage to a starting number to get a new value. Percentage change works in the other direction: you know both values and want to find the percentage between them. Use our percentage change calculator for that.

### Prime number & factor calculator
https://hopi.co.uk/prime-factorisation-calculator/

Free prime factorisation calculator. Check if a number is prime, get its prime factors in power form, and list every divisor and how many there are. Instant.

**What is a prime number?** A whole number greater than 1 whose only divisors are 1 and itself. The first few are 2, 3, 5, 7, 11 and 13. Numbers that are not prime, like 12 or 100, are called composite and can be broken down into smaller factors. The number 1 is neither prime nor composite by convention.

**What is prime factorisation?** Writing a number as a product of prime numbers only. Every whole number above 1 has exactly one such breakdown, a fact known as the fundamental theorem of arithmetic. For example, 360 factorises to 2 x 2 x 2 x 3 x 3 x 5, usually written 2^3 x 3^2 x 5 using powers.

**How does the calculator find the factors?** It uses trial division. It repeatedly divides by 2, then tests odd numbers upward, only needing to go as far as the square root of the number. Anything left over at the end is itself prime. This is fast for everyday numbers and copes with values up to a thousand trillion.

**Is there a limit on the number I can enter?** Yes, the tool accepts whole numbers up to 1,000,000,000,000,000 (ten to the power fifteen). Above that, ordinary computers lose exact precision with large integers, and factorising very large numbers is deliberately hard, which is the basis of a lot of modern encryption.

**How do I count the divisors quickly?** Take the prime factorisation, add one to each power, then multiply those together. For 360 = 2^3 x 3^2 x 5, that is (3+1) x (2+1) x (1+1) = 24 divisors. The calculator shows this count alongside the full list.

### Ratio calculator
https://hopi.co.uk/ratio-calculator/

Free ratio calculator. Simplify any ratio to its lowest terms or solve a missing value in an equivalent ratio. Instant answers for recipes, maps and screens.

**How do I simplify a ratio?** Divide both sides by their highest common factor (HCF), the largest whole number that divides into both. For 18 : 24 the HCF is 6, so the ratio simplifies to 3 : 4. When no whole number bigger than 1 divides both sides, the ratio is already in its simplest form.

**How do I find a missing value in a ratio?** Use cross multiplication. If A : B = C : x, then x = B multiplied by C, divided by A. For example, if 2 : 3 = 5 : x, then x = 3 multiplied by 5 divided by 2, which is 7.5.

**Can a ratio include decimals?** Yes, but the convention is to clear them before simplifying. Multiply both sides by 10 until both are whole numbers, then divide by the HCF as usual. So 2.5 : 1.5 becomes 25 : 15, which simplifies to 5 : 3. This calculator handles that step for you.

**What does 16 : 9 mean on a screen?** It is the aspect ratio, the width compared with the height. A full HD screen is 1920 by 1080 pixels, and 1920 : 1080 simplifies to 16 : 9 because both numbers divide by 120. Most modern TVs, laptops and YouTube videos use this shape.

**How do I split an amount in a given ratio?** Add the parts of the ratio together, divide the amount by that total, then multiply by each part. To split 120 pounds in the ratio 2 : 3, add 2 and 3 to get 5 parts, so each part is worth 24 pounds. The shares are 48 pounds and 72 pounds.

### Right-angle triangle calculator
https://hopi.co.uk/triangle-calculator/

Free right-angle triangle calculator. Enter any two of the sides or an angle and it finds the rest, plus the area and perimeter, showing the formula it used.

**What counts as a right-angle triangle?** One where a single interior angle is exactly 90 degrees. The side opposite that right angle is the hypotenuse, and it is always the longest side. The other two sides are called the opposite and the adjacent, named relative to whichever of the remaining angles you are looking at.

**What is Pythagoras theorem?** For a right-angle triangle, the square of the hypotenuse equals the sum of the squares of the other two sides, written a squared plus b squared equals c squared. It lets you find any one side when you know the other two. For example, sides of 3 and 4 give a hypotenuse of 5, because 9 plus 16 is 25.

**Which two values do I need to enter?** Any two, as long as one of them is a side. Two sides let the tool use Pythagoras and inverse trigonometry. One side plus one angle lets it use sine, cosine or tangent. Two angles alone are not enough because they fix the shape but not the size.

**Why do I get an impossible triangle warning?** The hypotenuse must be the longest side, so if you enter a hypotenuse that is shorter than or equal to another side, no right-angle triangle can exist. You will also see a warning if an angle is not between 0 and 90 degrees, since the third angle is already taken by the right angle.

**Does it work for non right-angle triangles?** No, this tool is specifically for right-angle triangles and assumes one angle is 90 degrees. Solving a general triangle needs the sine rule or cosine rule and at least three pieces of information, which is a different calculation.

### Roman numerals converter
https://hopi.co.uk/roman-numerals-converter/

Free Roman numerals converter. Type a number to get its Roman numeral, or type numerals to get the number, covering 1 to 3999 with instant validation.

**What do the Roman numeral letters stand for?** There are seven: I is 1, V is 5, X is 10, L is 50, C is 100, D is 500 and M is 1000. Values are added together from largest to smallest, so MMXXVI is 1000 + 1000 + 10 + 10 + 5 + 1, which is 2026.

**How does subtractive notation work?** When a smaller numeral sits before a larger one, it is subtracted instead of added. Only six pairs are allowed: IV is 4, IX is 9, XL is 40, XC is 90, CD is 400 and CM is 900. So 1994 is MCMXCIV, never MIM or other shortcuts.

**Why does the converter stop at 3999?** Standard Roman numerals repeat a letter at most three times, and there is no standard single letter above M for 1000, so 3999 (MMMCMXCIX) is the largest number that can be written conventionally. The Romans drew a bar called a vinculum over letters to multiply them by 1000, but there is no standard keyboard way to type it.

**Is IIII on a clock face wrong?** Not on a clock. Traditional clock and watch dials have long used IIII for 4, partly for visual balance with VIII on the opposite side. In every other modern context the standard form is IV, and that is what this converter produces.

**Why do films and TV shows use Roman numerals for the year?** It is a broadcasting and film tradition for copyright dates, so a title card reading MMXXVI means 2026. A cynical old explanation is that numerals made the production year harder to read at a glance, keeping repeats looking fresh. Sequels and events use them too, from Rocky IV to the Super Bowl.

### Rounding & significant figures calculator
https://hopi.co.uk/rounding-calculator/

Free rounding calculator. Round any number to your chosen decimal places or significant figures, with halves rounded up. Instant results in your browser.

**What is the difference between decimal places and significant figures?** Decimal places count digits after the decimal point, so 3.14159 to 2 decimal places is 3.14. Significant figures count digits from the first non-zero digit, wherever the decimal point falls, so 0.004567 to 2 significant figures is 0.0046 and 12,345 to 3 significant figures is 12,300.

**Which way does a 5 round in this tool?** Up, away from zero. So 2.5 rounds to 3, 3.45 to 1 decimal place is 3.5, and minus 2.5 rounds to minus 3. This is the round half up rule taught in UK schools and used by most calculators and spreadsheets.

**Why does 2.675 round to 2.68 here but 2.67 in some software?** Computers store decimals in binary, and 2.675 is actually stored as a value fractionally below 2.675. Naive code sees that lower value and rounds down to 2.67. This tool works from the number you typed, so 2.675 to 2 decimal places correctly gives 2.68.

**What is banker's rounding?** A rule where halves round to the nearest even digit, so 2.5 becomes 2 while 3.5 becomes 4. It avoids a small upward bias when summing lots of rounded values, and Python's built-in round function uses it. This tool deliberately does not; halves always round up.

**Do zeros count as significant figures?** Leading zeros never do: 0.0046 has 2 significant figures. Zeros between non-zero digits always do: 4,006 has 4. Trailing zeros are significant after a decimal point (2.400 has 4) but ambiguous in a whole number like 1,500, which is one reason scientists prefer standard form.

### Scientific calculator
https://hopi.co.uk/scientific-calculator/

Free online scientific calculator. Trigonometry, powers, roots, logs, factorials, brackets and memory, with degrees or radians. Works instantly in your browser.

**What order does the calculator work things out in?** It follows the standard order of operations, sometimes remembered as BODMAS or BIDMAS. Brackets are done first, then powers and roots, then multiplication and division, then addition and subtraction. So 2 + 3 x 4 gives 14, not 20, because the multiplication happens before the addition. Use brackets whenever you want to force a different order.

**How do I switch between degrees and radians?** Use the degrees and radians toggle above the keypad. It changes how the trigonometry buttons read their angles. In degrees, sin(30) gives 0.5. In radians, the same buttons expect the angle in radians, so you would enter sin(pi / 6) for the same result. Inverse functions like asin return the answer in whichever mode you have selected.

**What do the memory buttons do?** MC clears the stored memory, MR recalls it into your calculation, M+ adds the current value to memory and M- subtracts it. Memory is handy when you want to hold a running subtotal while working on another part of a sum, then bring it back later without writing it down.

**Does anything I type get sent anywhere?** No. Every calculation runs entirely in your browser using plain JavaScript. Nothing you type is uploaded, logged or stored on a server, so you can use it offline once the page has loaded.

**Why does dividing by zero show Error?** Dividing any number by zero has no defined answer in ordinary arithmetic, so the calculator shows Error rather than a misleading figure. You will also see Error for things like the square root of a negative number or the factorial of a fraction, which are undefined for a basic calculator.

### Standard deviation calculator
https://hopi.co.uk/standard-deviation-calculator/

Free standard deviation calculator. Paste your numbers to get sample and population standard deviation, variance, mean and count instantly in your browser.

**What does standard deviation actually tell me?** It measures how spread out your values are around the mean, in the same units as the data. A small standard deviation means the values cluster tightly around the mean; a large one means they are widely scattered. Two data sets can share a mean yet have completely different standard deviations.

**Should I use the sample or the population figure?** Use the population version only when your data is the entire group you care about, such as the test scores of every pupil in one class. Use the sample version when your data is a subset standing in for something bigger, which is the usual situation. If in doubt, use the sample figure.

**Why does the sample formula divide by n minus 1?** Because deviations are measured from the sample mean, which always sits conveniently in the middle of your sample, the raw average of squared deviations understates the true spread. Dividing by n minus 1 instead of n corrects this bias. The adjustment is called Bessel's correction.

**What is variance?** Variance is the standard deviation squared, the average of the squared deviations from the mean. It is central to statistics but awkward to interpret because its units are squared, for example pounds squared. Taking the square root gets you back to the data's own units, which is why standard deviation is quoted more often.

**What does a standard deviation of 0 mean?** Every value in the data set is identical, so there is no spread at all. The standard deviation can never be negative, because it is calculated from squared deviations, which are always zero or positive.

## Money & UK

### Bill splitter
https://hopi.co.uk/bill-splitter/

Free bill splitter. Add each item, tick who shared it, add a tip or service charge, and see exactly what every person owes, or just split the total evenly.

**How are shared items split?** Each item's cost is divided equally among the people ticked for it. If three people shared a bottle of wine, each of them is charged a third of it, while an item only one person had falls entirely to that person. Add up each person's share of every item and you get their subtotal before any tip.

**How do the tip and service charge get shared?** Both are entered as a percentage and applied to each person's own subtotal, so someone who ate more pays a proportionally larger share of the tip. That keeps the split fair without any awkward rounding. If your bill already lists a service charge as a percentage, put it in the service field.

**What if nobody is ticked for an item?** If an item has no one assigned, the calculator treats it as shared by everyone rather than dropping it, so the totals always add up to the full bill. A note tells you when this has happened, so you can tick the right people if it was a mistake.

**How is this different from the tip calculator?** The tip calculator splits one total evenly between a number of people. The bill splitter goes further: you list each item and say who had it, so people only pay for what they ordered. There is also a quick even-split mode here if that is all you need.

**Are the amounts I enter stored anywhere?** No. Everything is worked out in your browser as you type, and nothing is uploaded or saved to any server. Close the tab and the figures are gone. It is simply a faster, fairer way to settle up than passing a phone round the table.

### CAGR calculator
https://hopi.co.uk/cagr-calculator/

Free CAGR calculator. Enter a start value, end value and number of years to find the compound annual growth rate, total growth and the value year by year.

**What is CAGR?** CAGR stands for compound annual growth rate. It is the single steady yearly rate that would take your starting value to your ending value over the period, with compounding. Real investments never grow that smoothly, but CAGR gives you one honest number for comparing growth over different time spans.

**How is CAGR different from average annual return?** A simple average of yearly returns overstates growth because it ignores compounding. Gain 50% then lose 50% and your average is zero, but you actually end with 25% less money, a CAGR of about minus 13.4% a year. CAGR always reflects where you genuinely finished, which is why professionals prefer it.

**Can I use periods shorter than a year?** You can enter fractions of a year, such as 0.5 for six months, but treat the answer with care. Annualising a short period assumes the same pace continues all year, so a lucky quarter turns into a spectacular looking annual rate. The calculator flags this whenever the period is under a year.

**Does CAGR account for deposits and withdrawals?** No. CAGR assumes the change from start to end came entirely from growth. If you added or withdrew money along the way, the rate will be distorted. For a savings pattern with regular contributions, use the compound interest calculator instead.

**What does a negative CAGR mean?** It means the value fell over the period, and the figure is the steady yearly decline that produces that fall. For example £5,000 shrinking to £4,000 over 3 years is a CAGR of about minus 7.2% a year, even though the total drop is 20%.

### Compound interest calculator
https://hopi.co.uk/compound-interest-calculator/

Free compound interest calculator. Enter a deposit, monthly contribution, rate and term to see your final balance, total paid in and interest earned.

**What is compound interest?** Compound interest is interest paid on both your original money and on the interest it has already earned. Each period the balance grows, and the next round of interest is calculated on that bigger balance, so growth accelerates over time rather than staying flat.

**How often does this calculator compound?** Monthly, with contributions added at the end of each month. Most UK savings accounts calculate interest daily or monthly and pay it monthly or annually. The published AER lets you compare accounts on an equal footing whatever their compounding schedule.

**What is the difference between AER and the gross rate?** The gross rate is the flat annual rate before compounding is considered. AER (annual equivalent rate) shows what you would actually earn in a year once compounding is included, which is why AER is the number to compare between accounts.

**Is tax included in these figures?** No. The calculator shows growth before any tax. UK savers have a personal savings allowance, and interest earned inside a cash ISA is tax-free. If your interest will exceed your allowance, your real return will be lower than shown.

**What is the compound interest formula?** For a lump sum, the final value is P × (1 + r ÷ n) to the power of n × t, where P is the starting amount, r the annual rate as a decimal, n the number of compounding periods per year, and t the number of years. Regular contributions are added period by period on top of that.

### Currency converter
https://hopi.co.uk/currency-converter/

Free currency converter with live mid-market rates for 150+ currencies, updated hourly. Convert pounds, euros, dollars, yen and more, with the rate time shown.

**Where do the exchange rates come from?** From Open Exchange Rates, a widely used commercial rates provider. Hopi's own server fetches the latest rates once an hour and serves them from hopi.co.uk, so your browser never contacts a third party and nothing about you or your amounts is sent anywhere. The conversion itself runs entirely in your browser.

**How up to date are the rates?** They refresh every hour, and the tool shows the exact date and time (in UTC) of the rate set it is using, so there is no guesswork. Because the whole site shares one hourly update, everyone sees the same rate at the same time.

**Why is the rate different from what my bank or card gave me?** These are mid-market rates, roughly the midpoint between buying and selling prices in the wholesale market. Banks, cards and bureaux de change add a spread or fee on top, so the rate you actually get is always a little worse. Use the mid-market rate as the fair yardstick to compare offers against.

**What happens if the rates cannot be fetched?** If the rate service is briefly unreachable, Hopi's server keeps serving the last good rates it holds and labels them clearly with their time. If no rates can be loaded at all, the tool switches to a manual mode where you can type in a rate yourself.

**Which currencies are included?** More than 150 of the world's actively traded currencies, including the pound, euro, US dollar, yen, Swiss franc and the major Asian, Middle Eastern, African, Nordic and Commonwealth currencies. Precious metals and cryptocurrencies are not included.

### Day rate to salary calculator
https://hopi.co.uk/day-rate-calculator/

Free UK day rate calculator for contractors. Convert a day rate to an annual salary equivalent, or a salary to a day rate, with editable working days per year.

**Why does the calculator default to 220 working days?** A year has about 260 weekdays, but nobody bills all of them. Take off around 25 days of holiday, 8 bank holidays and a few days of sickness, training or gaps between contracts and you land near 220 billable days. It is a widely used planning figure, and you can change it to match your own year.

**Is a £400 day rate the same as an £88,000 salary?** No. The annual equivalent is gross billing only. An employee on £88,000 also gets paid holiday, sick pay, employer pension contributions of at least 3%, notice and redundancy rights. A contractor funds all of that from the day rate, plus insurance and accountancy costs, so the two numbers are not directly comparable.

**How do I convert a day rate to an hourly rate?** Divide the day rate by the hours in your working day. On £400 a day at 8 hours that is £50 an hour, or £53.33 at 7.5 hours. Check what a professional day means in your contract, because some clients specify 7.5 hours and others 8.

**What is IR35 and does it change these numbers?** IR35 (the off-payroll working rules) decides whether a contract is taxed like employment. It does not change your day rate, but it changes how much tax comes off it, sometimes substantially. This calculator compares gross amounts only. Check your status and the rules on gov.uk before relying on any net figure.

**Should I use 220, 230 or 260 days when setting a rate?** Use the number of days you realistically expect to bill. If you take less holiday and stay fully booked, 230 or 240 may fit. Using 260 assumes you bill every single weekday of the year with no holiday, illness or gaps, which almost never happens and makes a rate look better than it is.

### Energy running cost calculator
https://hopi.co.uk/energy-cost-calculator/

Free energy running cost calculator. Enter an appliance's wattage, hours of use per day and your electricity unit rate to see the cost per day, month and year.

**What is a kilowatt hour?** A kilowatt hour (kWh) is the unit your electricity bill charges in. It is 1,000 watts running for one hour, so a 100 W television on for 10 hours and a 2,000 W heater on for 30 minutes each use exactly 1 kWh. Your unit rate is the price you pay per kWh.

**Where do I find my electricity unit rate?** On a recent bill, in your supplier's app, or in your tariff details, listed as pence per kWh. Rates vary by supplier, region and payment method, and the price cap changes every three months, so check your own figure rather than using a number from the news.

**Why is my bill higher than the appliance costs I calculate?** Two main reasons. Your bill includes a standing charge, a fixed daily fee of tens of pence that you pay regardless of usage, and a home runs many loads at once: fridge, router, chargers, lighting, hot water and heating. Add the standing charge and the other appliances and the gap usually closes.

**Which appliances cost the most to run?** Anything whose main job is making heat: electric heaters, tumble dryers, ovens, immersion heaters, kettles and the heating phase of washing machines and dishwashers. Electronics like TVs, laptops and LED lighting are comparatively cheap even over long hours.

**Do appliances use electricity on standby?** Yes. Most modern devices draw a small amount, typically from under 1 W to around 10 W each, but a home full of them adds up to a constant trickle. Switching off genuinely unused devices at the wall, or on a standby-cutting extension lead, saves a modest but real amount over a year.

### Fuel cost calculator
https://hopi.co.uk/fuel-cost-calculator/

Free UK fuel cost calculator. Enter distance in miles, your car's mpg and the price per litre to see what a journey costs, with round trip and cost splitting.

**What mpg figure should I enter?** Your real-world figure, not the brochure one. Official WLTP figures are set in lab conditions and most drivers get 10% to 20% less. The most accurate source is your car's trip computer averaged over a few weeks, or a brim-to-brim calculation: fill the tank, drive, refill, and divide miles driven by gallons added.

**Why does the calculator mix miles per gallon with pence per litre?** Because that is the odd way the UK actually works. Fuel economy is quoted in miles per imperial gallon, but pumps sell fuel in litres. One imperial gallon is exactly 4.54609 litres, so the calculator converts gallons needed into litres before applying your pump price.

**Where do I find the current fuel price?** Check the pump, a recent receipt or a price comparison app before you calculate, because prices change weekly and vary a lot between forecourts. Supermarket stations are usually cheapest and motorway services are usually the most expensive, often by more than 20p a litre.

**Does this work for electric cars?** Not directly, because EV efficiency is measured in miles per kilowatt hour rather than miles per gallon. Divide your journey miles by your car's miles per kWh to get the energy needed, then price it with the energy running cost calculator using your home tariff or the public charger rate.

**How can I cut the cost per mile?** Drive smoothly, stick closer to 60 than 80 on faster roads, keep tyres at the right pressure, remove roof boxes and heavy clutter, and combine short cold-engine trips. Together these routinely improve consumption by 10% or more, which is the same as a 10% cut in pump prices.

### Holiday entitlement calculator
https://hopi.co.uk/holiday-entitlement-calculator/

Free UK holiday entitlement calculator. Enter your days per week (and part of year if joining or leaving) to see your statutory annual leave in days.

**How much holiday am I legally entitled to?** Statutory paid holiday in the UK is 5.6 weeks a year. For someone working 5 days a week that is 28 days; for 3 days a week it is 16.8 days. The statutory figure is capped at 28 days, so working 6 days a week does not raise it further.

**Are bank holidays on top of the 28 days?** Not necessarily. There is no legal right to time off on bank holidays: employers can count them within the 5.6 weeks. A common full-time package of 20 days plus 8 bank holidays exactly meets the statutory minimum. More generous contracts treat bank holidays as extra.

**What if I start or leave partway through the year?** Entitlement accrues in proportion to the part of the leave year you are employed. Working 6 months of the year on a 5-day week gives 14 days. Employers may round up (and often round to half-days) but must not round down.

**How does it work for irregular or zero-hours workers?** Since April 2024, holiday for irregular-hours and part-year workers accrues at 12.07% of hours worked in each pay period. Work 100 hours and you bank about 12 hours of paid leave. The 12.07% comes from 5.6 weeks divided by the 46.4 working weeks that remain.

**Can my employer give more than the statutory minimum?** Yes, and many do: 25 days plus bank holidays is a common UK package. The law only sets the floor of 5.6 weeks. Check your contract, because contractual holiday follows its own rules on things like carry-over.

### Hourly wage to salary converter
https://hopi.co.uk/hourly-to-salary/

Free hourly wage to salary converter for the UK. Turn an hourly rate into annual, monthly and weekly pay, or work out the hourly rate behind a salary.

**How do I convert an hourly wage to an annual salary?** Multiply your hourly rate by the hours you work each week, then by 52 weeks. For example £15 an hour at 37.5 hours a week is 15 x 37.5 x 52, which comes to £29,250 a year.

**Why multiply by 52 weeks when I get holiday?** Because UK employees get paid holiday, so you are paid for all 52 weeks of the year even though you only work around 46 or 47 of them. If your holiday is unpaid, for example on some casual contracts, multiply by the weeks you actually get paid instead.

**What counts as full-time hours in the UK?** There is no single legal definition, but 37.5 hours a week (7.5 hours a day excluding lunch) is the most common full-time pattern, with 40 hours also widespread. Your contract states your hours, and the Working Time Regulations cap the average week at 48 hours unless you opt out.

**How do I work out my hourly rate from my salary?** Divide your annual salary by 52 to get weekly pay, then divide by your weekly hours. On £30,000 at 37.5 hours a week that is 30,000 divided by 52 divided by 37.5, which is about £15.38 an hour.

**Are these figures before or after tax?** Before tax. Everything here is gross pay, so income tax, National Insurance, pension contributions and student loan repayments would still come off. Use a take-home pay calculator to see what actually lands in your account.

### Loan repayment calculator
https://hopi.co.uk/loan-calculator/

Free UK loan repayment calculator. Enter the amount, APR and term to see your monthly payment, total interest and the true cost of a personal loan.

**What does representative APR mean?** The advertised representative APR only has to be offered to 51% of accepted applicants. The other 49% can be offered a higher rate based on their credit history, income and the loan size. The rate you are actually quoted after applying is the one that matters.

**Is APR the same as the interest rate?** Not quite. APR is the total yearly cost of borrowing including compulsory fees, expressed as a percentage, which makes it the fairest number for comparing loans. On most personal loans with no arrangement fee the APR and interest rate are very close.

**Can I repay a personal loan early?** Yes. Under the Consumer Credit Act you can settle early at any time, and lenders can charge at most around one to two months of extra interest as compensation. Ask for a settlement figure, and check whether partial overpayments are allowed too, as they reduce the interest you pay.

**Why do smaller loans have higher APRs?** Lenders' fixed costs of setting up and running a loan are spread over less money, so rates on £1,000 to £3,000 loans are usually much higher than on £7,500 to £15,000, where the most competitive rates tend to sit. Sometimes borrowing slightly more actually costs less per pound.

**Does a longer term make a loan cheaper?** It lowers the monthly payment but raises the total cost, because interest is charged on the balance for longer. If you can manage the higher payment, a shorter term almost always means paying less overall.

### Margin & markup calculator
https://hopi.co.uk/margin-calculator/

Free margin and markup calculator. Enter cost and selling price to get profit, margin percentage and markup percentage instantly, with the formulas explained.

**What is the difference between margin and markup?** Margin is profit as a percentage of the selling price, markup is profit as a percentage of the cost. Buy at £60 and sell at £100 and the £40 profit is a 40% margin but a 66.7% markup. Markup is always the bigger number for the same sale.

**How do I price a product for a target margin?** Divide the cost by one minus the margin as a decimal. For a 60% margin on a £20 cost, that is 20 divided by 0.4, giving a selling price of £50. Adding 60% to the cost instead would give £32, which is only a 37.5% margin.

**Can margin or markup go over 100%?** Markup can, easily: selling a £20 item for £50 is a 150% markup. Margin cannot exceed 100% on a normal sale, because profit can never be more than the selling price. Margin only approaches 100% as the cost approaches zero.

**Should I use prices with or without VAT?** Work margins on VAT-exclusive figures if you are VAT registered. The VAT you charge belongs to HMRC, not you, so including it flatters the margin. Use the cost you actually pay (net of any VAT you reclaim) and your net selling price.

**What counts as a good profit margin?** It varies hugely by sector. Supermarkets survive on low single-digit net margins, while software businesses can run gross margins above 80%. Compare against your own industry, and remember gross margin ignores overheads, so net margin is always lower.

### Mortgage overpayment calculator
https://hopi.co.uk/mortgage-overpayment-calculator/

Free mortgage overpayment calculator. See how many years and how much interest a monthly overpayment saves on your UK mortgage, simulated month by month.

**How much can I overpay without a penalty?** Most fixed and discounted deals allow overpayments of up to 10% of the outstanding balance each year without charge. Go beyond that and an early repayment charge applies, typically 1% to 5% of the excess. Check your mortgage offer for the exact allowance, and note that many trackers and standard variable rates have no limit at all.

**Why does a small overpayment save so much?** Every extra pound goes straight at the balance, and interest is charged on the balance every month for the rest of the term. Killing £200 of balance today avoids interest on that £200 for what could be 20 years or more, which is why the savings compound into thousands.

**Should I reduce the term or reduce the payment?** When you overpay, lenders usually offer to either shorten the term or lower your future monthly payment. Shortening the term saves far more interest, because the debt is cleared sooner. Lowering the payment adds flexibility but keeps you borrowing for just as long.

**Is it better to overpay or put the money in savings?** Compare rates. If your mortgage rate is higher than the after-tax return on your savings, overpaying usually wins. If savings pay more, or you lack an emergency fund of 3 to 6 months of outgoings, building cash first is often the wiser move. Clearing expensive debts like credit cards should come before either.

**Does a one-off lump sum work the same way?** Yes, and often better, because the whole amount starts saving interest immediately. A lump sum early in the mortgage saves more than the same total spread over years of small payments. The same 10% annual allowance normally applies during a fixed deal.

### Mortgage repayment calculator
https://hopi.co.uk/mortgage-calculator/

Free UK mortgage repayment calculator. Enter the amount, interest rate and term to see your monthly payment, total repaid and total interest on the loan.

**What is the difference between repayment and interest-only?** A repayment mortgage clears both interest and a slice of the loan each month, so you owe nothing at the end of the term. Interest-only covers just the interest, leaving the whole loan to repay at the end. This calculator models a standard repayment mortgage.

**Why does a longer term cost so much more?** Stretching the term shrinks the monthly payment but leaves the balance outstanding for longer, and interest is charged on the balance every month. Moving a £200,000 loan at 4.5% from 25 to 30 years cuts the payment by about £98 a month but adds about £31,300 of interest over the life of the loan.

**Does this include fees, insurance or rate changes?** No. It assumes one constant interest rate for the whole term and ignores arrangement fees, valuation fees, buildings insurance and product switches. Most UK mortgages fix the rate for 2 to 5 years and then move to a different rate, so treat the totals as a like-for-like comparison tool.

**How much can I actually borrow?** Lenders typically offer around 4 to 4.5 times household income, adjusted for outgoings, credit history and the deposit you can put down. This calculator works the other way round: it shows what a given loan would cost, which helps you sanity-check whether the payment fits your monthly budget.

**Why is my lender's quote slightly different?** Lenders may charge interest daily rather than monthly, round payments differently, or add fees to the loan. Those details usually move the figure by pennies or a few pounds. Large differences normally mean a different rate, term or fee structure, so compare the full illustration.

### National Insurance calculator
https://hopi.co.uk/national-insurance-calculator/

Free UK National Insurance calculator for 2026/27. Enter your salary to see employee Class 1 NI for the year, month and week, plus your effective NI rate.

**How much National Insurance will I pay in 2026/27?** As an employee you pay nothing on the first £12,570 of annual earnings, 8% on earnings between £12,570 and £50,270, and 2% on everything above £50,270. On a £35,000 salary that works out at £1,794.40 for the year.

**What does National Insurance pay for?** NI contributions fund the state pension, contributory benefits such as New Style Jobseeker's Allowance and Employment and Support Allowance, and part of NHS funding. Paying NI also builds the qualifying years you need for a full state pension.

**Is National Insurance different in Scotland or Wales?** No. Unlike income tax, National Insurance rates and thresholds are set UK-wide, so the figures here apply in England, Scotland, Wales and Northern Ireland alike. Only income tax bands differ between the nations.

**Why is the NI on my payslip slightly different?** Employee NI is worked out separately on each payslip rather than on your annual total, so bonuses, overtime or uneven pay can shift the yearly amount slightly. Salary sacrifice arrangements, such as some pension schemes, also reduce the pay that NI is charged on.

**Do self-employed people pay the same National Insurance?** No. The self-employed pay Class 4 contributions on their profits through Self Assessment, at different rates from employees, and Class 2 is now largely voluntary. Check gov.uk for the current self-employed rates.

### Net to gross salary calculator
https://hopi.co.uk/net-to-gross/

Free UK net to gross salary calculator for 2026/27. Enter the take-home pay you want, yearly or monthly, and see the gross salary, income tax and NI behind it.

**How does the calculator find the gross salary?** There is no simple reverse formula, because the personal allowance, tax bands and two NI rates all switch on at different income levels. Instead the calculator repeatedly narrows down the answer: it tries a gross figure, works out the exact 2026/27 tax and National Insurance on it, compares the resulting take-home with your target and adjusts until the two match to within a penny.

**Does this work for Scotland?** Not exactly. The calculator uses the income tax bands for England, Wales and Northern Ireland. Scotland sets its own income tax bands and rates, so the gross salary needed for a given take-home is slightly different there, especially on middle and higher incomes. National Insurance is the same across the UK.

**Why is the real salary I need probably a bit higher?** The calculator models income tax and employee National Insurance on a standard tax code only. Pension contributions, student loan repayments, salary sacrifice and non-standard tax codes all reduce take-home pay further, so if any of those apply you will need a somewhat higher gross salary to hit the same target.

**Why does the required gross jump so much above £100,000?** Between £100,000 and £125,140 the personal allowance is withdrawn at £1 for every £2 earned, creating an effective 60% marginal tax rate before NI. In that window each extra £1 of take-home costs about £2.63 of gross salary, so take-home targets that land there need disproportionately large salaries.

**Should I enter a yearly or monthly figure?** Whichever you know. The monthly option simply multiplies your target by 12 and finds the annual gross salary behind it. Real payslips can differ slightly month to month because National Insurance is calculated per pay period rather than annually, but over a year the figures line up.

### Overtime pay calculator
https://hopi.co.uk/overtime-pay-calculator/

Free UK overtime pay calculator. Enter your hourly rate and hours at time and a half or double time to see the pay for each band and your shift total instantly.

**Am I legally entitled to time and a half for overtime?** No. UK law gives no right to a premium rate for overtime, or to any overtime pay at all beyond what your contract says. The only legal floor is that your average pay for the total hours you work in a pay reference period must not fall below the National Minimum Wage. Time and a half and double time exist only where a contract or collective agreement grants them.

**What do time and a half and double time actually mean?** They are multipliers on your basic hourly rate. Time and a half pays 1.5 times your normal rate, so £12.50 an hour becomes £18.75. Double time pays twice the rate, £25.00 in that example. Contracts typically reserve the higher multipliers for nights, weekends or bank holidays, but the details are whatever your contract says.

**Can my employer make me work overtime?** Only if your contract allows it, and even then your average working time cannot exceed 48 hours a week over a 17-week reference period unless you have voluntarily opted out in writing. Equally, an employer does not have to offer overtime, and can usually withdraw voluntary overtime when it chooses.

**Does overtime count towards holiday pay?** Often, yes. If overtime is regular enough to count as part of your normal pay, case law says it must be reflected in at least the 4 weeks of holiday derived from EU rules, and since 2024 the rules on what counts as normal remuneration are written into UK regulations. One-off, genuinely voluntary overtime may not count. Check how your employer calculates holiday pay if you work overtime most weeks.

**Is overtime taxed more than normal pay?** No, there is no special overtime tax rate. Overtime is added to your other pay and taxed under the same income tax bands and National Insurance rates. A month with a lot of overtime can be deducted more heavily through PAYE because that month's pay is higher, and a big overtime month can push some pay into a higher band, but the annual treatment is identical to ordinary wages.

### Pro-rata salary calculator
https://hopi.co.uk/pro-rata-salary-calculator/

Free pro-rata salary calculator. Enter the full-time salary and your weekly hours to see your part-time annual, monthly and weekly pay instantly.

**How is pro-rata salary worked out?** Divide your weekly hours by the full-time weekly hours, then multiply the full-time salary by that fraction. On 22.5 hours against a 37.5-hour week you work 60%, so a £30,000 full-time salary becomes £18,000.

**What counts as full-time hours?** There is no legal definition, but 37.5 hours is the most common UK full-time week, with 35 to 40 hours all normal. Use whatever the job advert or contract states as full-time, since that is the basis your employer will use.

**How do I calculate pro-rata from days instead of hours?** Divide days by 5 and use that fraction, assuming a 5-day full-time week. Three days a week is 3 ÷ 5 = 60% of the full-time salary, exactly equivalent to entering 22.5 hours against 37.5.

**Does part-time work change my hourly rate?** No. Pro-rata means proportional: you earn the same hourly rate as a full-time colleague, just for fewer hours. If the numbers you are offered work out to a lower hourly rate, that is not pro-rata and is worth querying.

**Is holiday also pro-rata?** Yes. Statutory holiday scales with your working pattern: 5.6 weeks of whatever your week looks like. Our holiday entitlement calculator does that sum.

### Redundancy pay calculator
https://hopi.co.uk/redundancy-pay-calculator/

Free UK statutory redundancy pay calculator. Enter your age, full years of service and weekly pay to see your entitlement using the 2026 caps and age bands.

**Who qualifies for statutory redundancy pay?** Employees with at least 2 full years of continuous service who are dismissed because the job itself is disappearing. You do not qualify with under 2 years' service, if you are self-employed, or usually if you turn down a suitable alternative role with the same employer without good reason.

**What counts as a week's pay?** Your average gross weekly earnings over the 12 weeks before you were given notice. For redundancies on or after 6 April 2026 it is capped at £751 a week, so higher earners have their entitlement worked out as if they earned £751. The overall statutory maximum is £22,530.

**Is redundancy pay taxed?** Statutory redundancy pay is tax-free, and the first £30,000 of any combined redundancy package is too. Anything above £30,000 is taxed as income. Payments that are really wages, such as notice pay and holiday pay, are taxed as normal regardless.

**Why do older years of service count for more?** The law credits each of your last 20 years of service by the age you were at the time: half a week's pay for years worked under 22, one week for years at 22 to 40, and one and a half weeks for years at 41 or over. The years are counted backwards from your redundancy date.

**Can my employer pay more than the statutory amount?** Yes. Statutory redundancy pay is only the legal minimum. Many employers offer enhanced redundancy packages in the contract or as part of a settlement agreement, often a multiple of the statutory figure or based on uncapped pay. Check your contract and any collective agreement.

### Savings goal calculator
https://hopi.co.uk/savings-goal-calculator/

Free savings goal calculator. Work out how long a target takes at your monthly deposit, or the amount needed each month to hit it by your deadline.

**How is the time to reach my goal worked out?** The calculator adds your monthly deposit at the end of each month and applies one month of interest on the running balance, month after month, until it reaches your target. It then reports the number of whole months, shown as years and months, because you cross the finish line partway through a month.

**What interest rate should I use?** Use the AER (annual equivalent rate) quoted on the savings account you plan to use. If you are saving in cash rather than an interest-paying account, enter zero and the tool simply adds your deposits up. Higher rates reach the goal sooner, but the deposits usually matter far more than the rate.

**Does this include tax on interest?** No. The figures are before any tax. Most people have a personal savings allowance, and interest inside a cash ISA is tax-free, but if your interest exceeds your allowance your real return will be a little lower than shown. The calculator focuses on the saving, not your tax position.

**What does monthly compounding mean here?** It means interest is worked out and added to the balance every month, so the following month's interest is calculated on a slightly larger amount. Most UK savings accounts behave close to this. The published AER already reflects compounding, so it is the fair figure to enter.

**Is this financial advice?** No. This is a guide to help you plan, not financial advice. Real accounts vary in how and when they pay interest, rates change over time, and your own circumstances matter. If you want tailored help, speak to a regulated adviser or see the free guidance at MoneyHelper on gov.uk.

### Stamp duty calculator
https://hopi.co.uk/stamp-duty-calculator/

Free UK stamp duty calculator for England and Northern Ireland. Work out SDLT for first-time buyers, home movers and additional properties, band by band.

**Do first-time buyers pay stamp duty?** Often not. First-time buyers pay nothing on the first £300,000 and 5% on the portion between £300,000 and £500,000. If the price is above £500,000 the relief disappears entirely and standard rates apply to the whole purchase. To qualify, every buyer must never have owned property anywhere in the world.

**When and how is stamp duty paid?** An SDLT return must be filed and the tax paid within 14 days of completion. In practice your conveyancer or solicitor almost always files the return and pays HMRC on your behalf, collecting the money from you as part of the completion funds.

**Does this calculator work for Scotland and Wales?** No. Scotland charges Land and Buildings Transaction Tax and Wales charges Land Transaction Tax, both with their own bands and rates. This calculator covers Stamp Duty Land Tax, which applies in England and Northern Ireland only.

**What counts as an additional property?** Buying a second home, holiday home or buy-to-let while you still own another residential property, where the new purchase is £40,000 or more. The higher rates add 5 percentage points to every band. If you are replacing your main home but have not yet sold the old one, you pay the surcharge up front and can reclaim it if you sell the previous home within 36 months.

**Do I pay the top rate on the whole price?** No. SDLT is a banded tax, like income tax. Each slice of the price is taxed at its own rate, so a £300,000 home is charged 0% on the first £125,000, 2% on the next £125,000 and 5% only on the final £50,000.

### Student loan repayment calculator
https://hopi.co.uk/student-loan-calculator/

Free UK student loan repayment calculator for 2026/27. Pick Plan 1, 2, 4, 5 or Postgraduate, enter your salary and see monthly and yearly repayments instantly.

**Which student loan plan am I on?** It depends on where you lived and when you started. Plan 1: England or Wales before September 2012, or Northern Ireland any year. Plan 2: England or Wales from September 2012 to July 2023. Plan 4: Scotland. Plan 5: England from August 2023. Postgraduate Loans are separate and cover master's and doctoral study in England and Wales.

**When is my student loan written off?** Plan 1 loans are written off 25 years after the April you were first due to repay (or at age 65 for the earliest loans). Plan 2 and Plan 4 loans are written off after 30 years, and Postgraduate Loans after 30 years too. Plan 5 loans last longest, written off 40 years after the April you were first due to repay.

**Why is the deduction on my payslip slightly different?** Payroll works out student loan deductions per pay period, not annually, and rounds each deduction down to a whole pound. Bonuses or overtime in a single month can also push that month's pay over the monthly threshold even if your annual salary is below it. This calculator shows the annual picture.

**Do I repay undergraduate and postgraduate loans at the same time?** Yes. If you have both, the two repayments run side by side: 9% of income above your undergraduate plan threshold plus 6% of income above the £21,000 postgraduate threshold. Tick the postgraduate box in the calculator to see the combined total.

**Does the interest rate change what I repay each month?** No. Repayments depend only on your income and your plan's threshold, so a higher interest rate never raises your monthly payment. Interest changes how fast the balance grows and therefore how long you repay, and whether you clear the loan before it is written off.

### Take-home pay calculator
https://hopi.co.uk/take-home-pay-calculator/

Free UK take-home pay calculator for the 2026/27 tax year. Enter your salary to see income tax, National Insurance and your monthly and weekly take-home pay.

**Why is my payslip different from this calculator?** This calculator shows income tax and employee National Insurance only, using the standard tax code (1257L). Payslips often also deduct pension contributions, student loan repayments, salary-sacrifice benefits or use a non-standard tax code, all of which change the final figure.

**What is the personal allowance and how does it disappear?** The first £12,570 you earn is tax-free. Above £100,000 the allowance shrinks by £1 for every £2 of income, vanishing entirely at £125,140. That taper creates an effective 60% tax rate on income between £100,000 and £125,140.

**Does this work for Scotland?** Not exactly. Scotland sets its own income tax bands (six of them in 2026/27), so Scottish taxpayers will see slightly different tax figures, especially on middle and higher incomes. National Insurance is the same UK-wide.

**How is National Insurance worked out?** Employees pay 8% on earnings between £12,570 and £50,270 a year, and 2% on everything above that. NI is actually calculated on each payslip rather than annually, so people with very uneven pay can see small differences from the annual figure shown here.

**Is overtime, bonus or pension included?** Enter your total expected gross pay including bonus and overtime for the year to see the tax on it. Pension contributions are not modelled: workplace pension contributions usually reduce your taxable pay, so with a pension your take-home will differ from the figure shown.

### Tip calculator
https://hopi.co.uk/tip-calculator/

Free UK tip calculator. Enter the bill, pick 10%, 12.5%, 15% or your own rate, and instantly see the tip, the total and each person's share of the bill.

**How much should you tip in the UK?** Around 10% to 12.5% in restaurants with table service is the usual range, rising towards 15% for outstanding service. Tipping is not expected in pubs, at counters or for takeaway. For taxis, many people simply round up to a convenient amount. Tipping in the UK is always discretionary.

**Do I need to tip on top of a service charge?** No. If the bill already includes a service charge, often 12.5% in London restaurants, that is the tip. You are not expected to add more. A discretionary service charge is optional, so you can ask for it to be removed if the service was poor, and tip in cash instead or not at all.

**Does my tip actually reach the staff?** It should. Under the Employment (Allocation of Tips) Act 2023, in force since 1 October 2024, employers must pass on 100% of tips, gratuities and service charges to workers without deductions, and distribute them fairly by the end of the following month. This covers card tips as well as cash.

**Should I tip on the amount before or after a discount?** Convention is to tip on the full pre-discount amount, since the staff did the same work regardless of your voucher or meal deal. UK menu prices already include VAT, so there is no separate pre-tax figure to worry about, unlike in the United States.

**Is it better to tip in cash or by card?** Either works. Since October 2024 both are legally protected and must go to staff in full. Cash sometimes reaches the team the same evening, while card tips are pooled and paid through payroll, but the law requires distribution by the end of the month after you paid.

### UCAS points calculator
https://hopi.co.uk/ucas-points-calculator/

Free UCAS points calculator. Enter your A-level grades to get your total tariff points instantly, using the official tariff values for A* to E.

**How many UCAS points is each A-level grade worth?** On the current UCAS tariff an A* is 56 points, an A is 48, a B is 40, a C is 32, a D is 24 and an E is 16. So AAB is 136 points and three A* grades come to 168.

**Do AS levels count towards UCAS points?** Yes, a standalone AS level is worth 40% of the full A-level grade: 20 points for an A, 16 for a B, 12 for a C, 10 for a D and 6 for an E. If you went on to complete the full A-level in the same subject, only the A-level counts, not both.

**Do BTECs earn UCAS points?** Yes. BTEC Nationals sit on the same tariff, with points depending on the size of the qualification and the grades. Because the combinations are extensive, check the official UCAS tariff tables for your exact BTEC and grade.

**Do GCSEs count towards UCAS points?** No. GCSEs carry no tariff points, however good the grades. Universities look at GCSEs separately, often requiring specific grades in English and maths, but they never add to your points total.

**How many UCAS points do I need for university?** It depends entirely on the course. Some universities make points-based offers, others ask for specific grades such as AAB, and many competitive courses will not count points from certain qualifications. Always check the entry requirements for each course on the UCAS website.

### UK inflation calculator
https://hopi.co.uk/inflation-calculator/

Free UK inflation calculator. See what money from any year since 1988 is worth today using official ONS CPI figures, or apply your own average rate.

**Where does the inflation data come from?** From the Office for National Statistics. The calculator uses the CPI all items index (series D7BT, 2015 = 100) as annual averages, covering 1988 to 2025, the latest complete year. The figures were downloaded from ons.gov.uk and cross-checked against a second published source before being included.

**What is the difference between CPI and RPI?** CPI (the Consumer Prices Index) is the UK's headline inflation measure and the one used here. RPI (the Retail Prices Index) is an older measure with a different formula and coverage that usually produces higher figures. RPI lost its national statistic status in 2013, though it still appears in some contracts and rail fare rises.

**Why do the results only go back to 1988?** The official CPI index starts in 1988. The ONS publishes modelled estimates for earlier years, but they are not part of the official series, so this calculator sticks to the confirmed data. For a longer historical view, the Bank of England publishes its own inflation calculator going back centuries.

**Can I estimate future inflation?** Not from the CPI data, because nobody knows future inflation rates. Use the custom rate mode instead: pick an assumed average rate, say 2% (the Bank of England's target), and a number of years, and the calculator compounds it for you. Treat the result as a what-if, not a forecast.

**Why does the calculator use annual averages rather than monthly figures?** Because the question people actually ask is what an amount from a given year is worth now. Annual averages smooth out month-to-month noise and match how the ONS reports calendar-year inflation. If you need month-level precision, the full monthly index is available free on the ONS website.

### Unit price comparison
https://hopi.co.uk/unit-price-calculator/

Free unit price comparison tool. Enter the price and size of up to four items to see the price per kg, litre or unit and which one is the best value.

**How do I compare products of different sizes?** Enter each product's price and its size, and pick the unit it is sold in. The tool divides the price by the size to give a price per standard unit, so a 500g pack and a 1kg pack are both shown per kg. The lowest price per unit is the best value, whatever the pack size.

**What counts as the standard unit here?** Weights in grams or kilograms are shown per kilogram. Volumes in millilitres or litres are shown per litre. Items counted individually, like tins or toilet rolls, are shown per item. That way every product in the same family lines up on the same scale.

**Why is the bigger pack not always cheaper?** Larger packs usually cost less per unit, but not always. Multipacks, promotions on small sizes and premium ranges can flip the maths, so the only reliable way to know is to compare the price per unit rather than the price on the shelf.

**Can I compare items sold by weight against items sold by volume?** Not meaningfully. A price per kilogram and a price per litre measure different things, so comparing them tells you nothing. Keep the items you compare in the same family, either all by weight, all by volume or all by count. The tool warns you if you mix them.

**Does the shelf label not already show this?** UK shops must show a unit price on shelf edge labels, but the units are not always consistent between products, and online baskets or market stalls may not show one at all. This tool lets you check for yourself and settle it in seconds.

### VAT calculator
https://hopi.co.uk/vat-calculator/

Free UK VAT calculator. Add VAT to a net price or remove VAT from a gross price at 20%, 5% or any custom rate. Instant net, VAT and gross breakdown.

**How do I take 20% VAT off a price?** Divide the VAT-inclusive price by 1.20. A gross price of £120 divided by 1.20 gives a net price of £100, so the VAT was £20. Do not multiply by 0.80, which takes 20% off the gross figure and gives the wrong answer (£96 instead of £100).

**What are the current UK VAT rates?** The standard rate is 20% and applies to most goods and services. The reduced rate is 5% and covers things like home energy and children's car seats. The zero rate (0%) covers most food, books, newspapers and children's clothes. Some items, such as postage stamps and financial services, are exempt from VAT altogether.

**What is the VAT registration threshold?** A business must register for VAT once its taxable turnover passes £90,000 in any rolling 12-month period. Businesses below the threshold can register voluntarily, which lets them reclaim VAT on purchases.

**Is VAT the same across England, Scotland, Wales and Northern Ireland?** Yes. VAT is a UK-wide tax set by the UK government, so the same rates apply in all four nations. Northern Ireland has some special rules for goods traded with the EU, but the rates themselves are the same.

**Do I pay VAT on food?** Most everyday food and drink from a supermarket is zero-rated, so no VAT is charged. However, standard-rate VAT at 20% applies to hot takeaway food, restaurant meals, alcohol, confectionery, crisps, soft drinks and bottled water.

## Text & writing

### Alphabetical order sorter
https://hopi.co.uk/alphabetical-order/

Free alphabetical order sorter. Sort any list A to Z or Z to A instantly, with numbers sorted naturally, then copy the result. Nothing is uploaded.

**How are numbers sorted?** Naturally, the way a person would sort them. Lines like item2 and item10 come out as item1, item2, item10 rather than the item1, item10, item2 a plain character sort produces, and all-number lines such as 5, 40 and 100 sort by value. This matters for file names, versions and anything with a counter in it.

**What does the ignore case option do?** With the box ticked, capitalisation is ignored while sorting, so apple and Apple sit together. Untick it and capitalisation becomes a tiebreaker for otherwise identical words, though words still sort together alphabetically rather than all capitals first. Ticked is the right choice for almost every everyday list.

**What happens to blank lines?** They are removed. A sort would otherwise sweep every blank line to one end of the list, which is never useful, so the tool drops them and returns just your items in order. Spacing inside lines is left exactly as you pasted it.

**Can I sort a comma-separated list?** The tool sorts lines, so put each item on its own line first. The quickest way is to paste your text into a word processor and replace each comma with a line break, or simply press Enter after each comma yourself. Once each item has its own line, paste the list here.

**Is my list uploaded anywhere?** No. The sorting happens in your browser using JavaScript and your list never leaves your device. Refreshing the page clears everything.

### Caesar cipher & ROT13
https://hopi.co.uk/caesar-cipher/

Free Caesar cipher and ROT13 tool. Shift letters to encode or decode a message live, with any shift from 0 to 25. Runs in your browser, nothing uploaded.

**What is a Caesar cipher?** It is one of the oldest and simplest ways to disguise a message: every letter is moved along the alphabet by a fixed number of places. Shift by 3 and A becomes D, B becomes E, and so on, wrapping round from Z back to A. It is named after Julius Caesar, who is said to have used a shift of 3 for his private letters.

**What is ROT13 and why is it special?** ROT13 is a Caesar cipher with a shift of exactly 13, which is half of the 26-letter alphabet. Because 13 plus 13 is 26, applying it twice returns the original text, so the same operation both encodes and decodes. That symmetry is why this tool defaults to a shift of 13.

**Is a Caesar cipher secure?** No. Treat it as a puzzle or a bit of fun, never as real protection. There are only 25 possible shifts, so anyone can try them all in seconds, and the letter patterns give it away instantly. Never use it for passwords, private messages or anything that actually needs to stay secret; use proper encryption for that.

**What happens to numbers, spaces and punctuation?** Only the 26 letters A to Z are shifted. Spaces, digits, punctuation and symbols are left exactly as they are, and the upper or lower case of each letter is preserved. That keeps the shape of the message readable while the letters are scrambled.

**How do I decode a message someone sent me?** If you know the shift, switch to decode, set the same shift and paste the text in. If you do not know it, try decode and drag the slider through the shifts until readable English appears. For ROT13 you do not even need to decide, since encode and decode with a shift of 13 give the same result.

### Case converter
https://hopi.co.uk/case-converter/

Free case converter. Change text to uppercase, lowercase, title case or sentence case in one click, then copy the result. Runs entirely in your browser.

**What is the difference between title case and sentence case?** Title Case Capitalises Each Word, and is used for headlines and titles. Sentence case capitalises only the first word of each sentence (plus anything you have capitalised yourself elsewhere is reset), and is how normal prose is written.

**Should small words be capitalised in title case?** Most style guides lowercase short words like a, an, the, of and in unless they start the title, but the rules differ between guides. This tool capitalises every word for predictability; lowercase the small words afterwards if your style guide wants that.

**Will sentence case fix names and places?** No. Converting to sentence case lowercases everything after the first letter of each sentence, including proper nouns like London or Sarah, because the tool cannot know which words are names. Skim the result and restore capitals where needed.

**Why does my pasted text arrive in capitals in the first place?** Usually because it was typed with caps lock on, exported from an old system that stores everything uppercase, or copied from a heading. Converting to sentence case and then fixing names is far faster than retyping.

**Is my text uploaded anywhere?** No. The conversion happens in your browser and the text never leaves your device.

### Character counter
https://hopi.co.uk/character-counter/

Free character counter. Count characters with and without spaces live as you type, plus SMS message parts and how much of the 280-character limit remains.

**Do spaces count as characters?** Yes. Almost every limit you will meet (UCAS, SMS, X, meta descriptions, application forms) counts spaces, punctuation and line breaks as characters. This tool shows both figures so you can use whichever the form asks for.

**Why does one text message sometimes cost several SMS parts?** A single SMS holds 160 characters. Go over and the message is split into parts of 153 characters each (7 are used to stitch the parts together). Emoji or special symbols switch the whole message to a different encoding where the limits drop to 70 and 67.

**Does the UCAS personal statement limit include spaces?** Yes. The 4,000-character UCAS limit includes spaces and line breaks, and there is also a 47-line limit. The characters-with-spaces figure is the one to watch.

**How many characters is a tweet allowed?** 280 for standard accounts on X, with links counted as 23 characters regardless of length. This page shows how many of the 280 you have used and how many remain.

**Is my text stored anywhere?** No. Counting happens in your browser as you type and nothing is sent to any server. Refreshing the page clears the text.

### Duplicate line remover
https://hopi.co.uk/remove-duplicate-lines/

Free duplicate line remover. Paste any list to delete repeated lines instantly, keeping the first of each in the original order. Nothing is uploaded.

**Which copy of a duplicate line is kept?** The first one. The tool reads your list from top to bottom, keeps a line the first time it appears and deletes every later repeat, so the surviving lines stay in their original order. If you want the list sorted afterwards, the alphabetical order sorter will do that.

**What does the ignore case option do?** With the box ticked, lines that differ only in capitalisation count as the same line, so Apple, apple and APPLE become one entry. The first version to appear is the one that survives, keeping its own capitalisation. Untick the box to treat differently capitalised lines as different entries.

**Why are two lines that look identical not being matched?** Almost always invisible characters. A trailing space, a tab, or a non-breaking space copied from a web page makes two lines different even though they look the same on screen. Run the list through the remove extra spaces tool first, then dedupe it.

**Are blank lines treated as duplicates?** Yes. Blank lines are compared like any other line, so the first blank line is kept and the rest are removed. If you want no blank lines at all, tidy the list with the remove extra spaces tool and its remove blank lines option first.

**Is my list uploaded anywhere?** No. The deduplication happens in your browser using JavaScript, so email lists, customer names and anything else sensitive never leave your device. Refreshing the page clears everything.

### Emoji remover
https://hopi.co.uk/emoji-remover/

Free emoji remover. Strip every emoji from text, including flags, skin tones, keycaps and joined sequences, see how many were removed and copy the clean result.

**Why does a family emoji count as one removal?** Many emoji are really several characters glued together with an invisible zero-width joiner. A family can be four person emoji joined into one picture, and a thumbs up with a skin tone is the base emoji plus a modifier. The tool removes each glued sequence as a unit and counts it once, which matches what you saw on screen.

**Does it remove copyright and trademark symbols?** Plain text symbols like the copyright sign, registered sign and trademark sign are kept, even though Unicode technically groups them with pictographs. If one has been styled as a colourful emoji using a variation selector, that emoji form is removed like any other.

**Why are there double spaces left where emoji used to be?** The tool removes only the emoji themselves and never touches your other characters, so an emoji that sat between two spaces leaves both spaces behind. Run the result through the remove extra spaces tool on this site to collapse them in one click.

**Are hearts, stars and other symbols removed too?** Yes. Hearts, stars, weather signs, zodiac signs and similar pictographs are part of the emoji set in Unicode, so they are stripped along with faces and flags. Ordinary punctuation, letters, numbers and accented characters are always left alone.

**Is my text uploaded anywhere?** No. The emoji detection runs in your browser using a Unicode-aware pattern, and nothing you paste ever leaves your device.

### Find and replace
https://hopi.co.uk/find-and-replace/

Free online find and replace tool. Search text with case sensitive, whole word or regex options, watch a live match count and replace every occurrence at once.

**Why does the match count show a dash?** A dash means there is nothing to count yet: either the find box is empty, or regex mode is on and the pattern is invalid. Invalid patterns also show an error message under the options explaining what the browser rejected. Fix the pattern or type something to search for and the count returns.

**What does the whole words option do?** It only matches your search term where it stands alone as a word, with word boundaries on both sides. Searching for cat with whole words on matches cat but not category or scattered. It works in plain mode and regex mode alike.

**What is regex mode?** Regex (regular expressions) is a pattern language, so instead of finding exact text you can find shapes of text, such as any four-digit number or anything inside brackets. Tick the box and the find field is treated as a pattern rather than literal characters. If you are new to regex, the regex tester on this site is a safe place to experiment.

**Can I use capture groups like $1 in the replacement?** Yes, in regex mode. Wrap parts of the pattern in round brackets and refer to them as $1, $2 and so on in the replace field, which is how you reorder dates or swap two words around. In plain mode a dollar sign is treated as an ordinary character and inserted literally.

**Is my text uploaded anywhere?** No. The searching and replacing run entirely in your browser using JavaScript, and your text never leaves your device.

### Lorem ipsum generator
https://hopi.co.uk/lorem-ipsum-generator/

Free lorem ipsum generator. Create classic placeholder paragraphs, sentences or words for mock-ups and layouts, then copy in one click. Runs in your browser.

**What does lorem ipsum actually mean?** Nothing readable. It is scrambled Latin based on a passage from Cicero's De finibus bonorum et malorum, written in 45 BC. Words have been altered, chopped and reordered over the centuries, so the text looks like language without saying anything.

**Why use placeholder text instead of real words?** Readable text pulls attention to its meaning, so reviewers start editing the copy instead of judging the layout. Lorem ipsum has a natural distribution of word lengths without any meaning, which keeps everyone focused on spacing, hierarchy and type.

**Is lorem ipsum free to use?** Yes. The text is a scrambled fragment of a 2,000-year-old work and has been used as printer's filler since at least the 1500s. There is no copyright to worry about, in personal or commercial projects.

**Why does it always start with Lorem ipsum dolor sit amet?** Convention. The standard passage begins with that phrase, and starting from it makes the text instantly recognisable as filler rather than forgotten draft copy. This generator always starts from the beginning of the classic passage for that reason.

**How much placeholder text do I need?** As a rough guide, a hero heading and standfirst need 20 to 30 words, a body paragraph 40 to 60 words, and a typical blog post layout 600 to 800 words. Generate slightly more than you think you need so you can see how the design copes.

### Morse code translator
https://hopi.co.uk/morse-code-translator/

Free Morse code translator. Turn text into Morse code or decode Morse back to text with the full international table. Runs in your browser, nothing uploaded.

**Why is SOS dot dot dot, dash dash dash, dot dot dot?** SOS was chosen in the early 1900s purely because the pattern is simple, unmistakable and easy to send under pressure. It does not stand for save our souls or anything else; the letters were picked to fit the signal, not the other way round. It is sent as one continuous sequence with no letter gaps.

**How are letters and words separated?** This tool puts a single space between letters and a forward slash with spaces around it between words, which is the common written convention. In transmitted Morse the separation is done with silence: the gap between letters is three units long and the gap between words is seven.

**Which characters can it translate?** All 26 letters, the digits 0 to 9, and the punctuation in the international standard: full stop, comma, question mark, apostrophe, slash, brackets, colon, hyphen, quotation mark, equals, plus and at sign, plus a few common extensions such as the exclamation mark. Anything else is flagged below the output rather than silently dropped.

**Does Morse code have lowercase letters?** No. Morse has one code per letter with no case distinction, so this tool treats upper and lower case identically. Decoded text is shown in capitals, which is the tradition inherited from telegraph operators.

**Is anything I type uploaded?** No. The translation runs entirely in your browser using an embedded code table. Nothing you type leaves your device, and refreshing the page clears it.

### NATO phonetic alphabet translator
https://hopi.co.uk/nato-phonetic-alphabet/

Free NATO phonetic alphabet translator. Spell any word or code as Alfa Bravo Charlie, and turn spoken spelling back into text. Runs in your browser.

**What is the NATO phonetic alphabet for?** It gives every letter a distinct code word so that spelling survives a bad phone line, a noisy room or a radio full of static. B and D or M and N sound almost identical over the phone, but Bravo and Delta, or Mike and November, never get confused. It is used by pilots, the emergency services, call centres and anyone reading out a reference, postcode or name.

**Is it Alfa or Alpha, Juliett or Juliet?** The official spellings are Alfa and Juliett. They look odd because the alphabet is international, and the unusual spellings stop speakers of other languages mispronouncing them. Alfa avoids the ph sound that some languages lack, and the double t in Juliett keeps French speakers from leaving the t silent. This tool accepts the common Alpha and Juliet spellings when translating back to text.

**How are numbers and spaces handled?** Digits are spelled as plain words, so 2 becomes Two and 0 becomes Zero. A space between words is shown as (space) so the gaps in a code like a postcode are not lost. When you translate spoken spelling back to text, (space) is turned back into a real space.

**Is this the same as the police or aviation alphabet?** Yes. The version most people mean by the police alphabet, the military alphabet or the aviation alphabet is this same set of 26 code words, formally the ITU and NATO phonetic alphabet adopted in the 1950s. Some older or regional services used different words, but Alfa through Zulu is the standard almost everywhere today.

**Is anything I type uploaded?** No. The translation runs entirely in your browser using an embedded code table. Nothing you type leaves your device, and refreshing the page clears it.

### Online notepad
https://hopi.co.uk/online-notepad/

Free online notepad that autosaves to your browser as you type. Word and character counts, copy and download as .txt. Nothing is ever uploaded anywhere.

**Where are my notes saved?** In your browser's local storage, on your device. Nothing is sent to any server, so your notes survive a refresh or an accidental tab close but are only available in this browser on this device.

**Will my notes sync to my phone or another computer?** No. Local storage lives inside one browser on one device, so notes written here on your laptop will not appear on your phone. If you need your notes elsewhere, use the Download button and move the .txt file yourself.

**Can my notes be lost?** Yes, in two situations. Clearing your browsing data (cookies and site data) deletes local storage, and private or incognito windows throw it away when they close. Download anything important as a .txt file to be safe.

**Is there a size limit?** Browsers typically allow around 5 MB of local storage per site, which works out at well over a million characters of plain text. That is far more than any normal note; a full novel is roughly 500,000 characters.

**Is anything I type uploaded or visible to anyone?** No. The page has no server component for your text at all. Everything you type stays in your browser, and the autosave writes only to your own device's storage.

### Reading time calculator
https://hopi.co.uk/reading-time-calculator/

Free reading time calculator. Paste your text to see how long it takes to read silently or out loud, plus a live word count. Instant, and nothing is uploaded.

**How is reading time worked out?** The tool divides your word count by 225 words per minute, a typical adult silent-reading pace, and rounds to the nearest second. Speaking time uses 130 words per minute, which suits speeches and presentations delivered at a comfortable pace.

**How long should a 5-minute speech be?** About 650 words. At a speaking pace of 130 words per minute, 5 minutes of talking is 5 times 130, which is 650 words. A 10-minute talk is roughly 1,300 words and a 20-minute talk roughly 2,600.

**Why do other sites give a different reading time?** They assume a different reading speed. Estimates across the web range from about 200 to 300 words per minute, so the same article can be labelled 4 minutes on one site and 6 on another. This tool uses 225 words per minute, a widely used middle figure for adult silent reading.

**Is 225 words per minute right for every kind of text?** No, it is an average for ordinary prose. Dense or technical material can drop readers to 150 words per minute or less, while skimming familiar content can be much faster. Treat the result as a good estimate rather than a stopwatch.

**Is my text stored or uploaded anywhere?** No. The counting and timing happen entirely in your browser using JavaScript. Nothing you type or paste leaves your device, and refreshing the page clears it.

### Remove extra spaces
https://hopi.co.uk/remove-extra-spaces/

Free extra space remover. Collapse repeated spaces and tabs, trim line ends and strip blank lines instantly, then copy the clean text. Nothing is uploaded.

**Should there be one space or two after a full stop?** One. The two-space habit comes from typewriters, where every character was the same width and the extra gap helped sentences stand apart. Modern fonts space sentences properly on their own, and most style guides, including UK publishers and gov.uk, use a single space.

**Does it remove tabs and non-breaking spaces?** Yes. Runs of ordinary spaces, tabs and non-breaking spaces (the invisible characters often copied from web pages) are all collapsed to a single ordinary space. That matters because a non-breaking space looks identical on screen but behaves differently in searches and comparisons.

**Will it break my code or indentation?** It will remove it. Leading spaces are trimmed from every line, so indented code, especially Python where indentation is part of the syntax, should not go through this tool. It is designed for prose, lists and data where the spacing is accidental rather than meaningful.

**What does the remove blank lines option do?** With the box ticked, any line that is empty, or contains only spaces and tabs, is deleted entirely, pulling the remaining lines together. Leave it unticked to keep your paragraph gaps and only tidy the spacing within lines.

**Is my text uploaded anywhere?** No. The clean-up happens in your browser using JavaScript and the text never leaves your device. Refreshing the page clears everything.

### Remove line breaks
https://hopi.co.uk/remove-line-breaks/

Free line break remover. Paste text with unwanted breaks and get one clean block or tidy paragraphs instantly, then copy the result. Nothing is uploaded.

**Why does text copied from a PDF have a break at the end of every line?** PDFs store text as printed lines rather than flowing paragraphs, so every visual line ending in the document becomes a hard break when you copy it. The text looked right at the PDF's width, but pasted anywhere else the breaks land mid-sentence. Emails, subtitles and scanned documents cause the same problem for similar reasons.

**What is the difference between the two modes?** Remove every break joins the whole text into one continuous block, replacing each break with a space. Keep paragraph breaks treats a blank line as a paragraph boundary, joins the lines within each paragraph, and leaves one empty line between paragraphs. Use the first for a single chopped-up paragraph and the second for longer passages.

**Will it merge my bullet list into one line?** In remove-every-break mode, yes, every line is joined, which is rarely what you want for a list. If your list items are separated by blank lines, keep-paragraph-breaks mode will preserve them as separate blocks. For lists it is usually better to keep one item per line and tidy them another way.

**Does it fix doubled spaces as well?** It trims spaces from the ends of lines before joining and collapses any doubled spaces the join itself would create, so the output reads cleanly. It does not hunt down every repeated space inside your original text. For a full spacing clean-up, run the result through the remove extra spaces tool afterwards.

**Is my text uploaded anywhere?** No. The processing happens in your browser using JavaScript and the text never leaves your device. Refreshing the page clears everything.

### Reverse text generator
https://hopi.co.uk/reverse-text/

Free reverse text generator. Reverse every character, flip the word order or mirror each word's letters as you type, then copy any output. Nothing is uploaded.

**What is the difference between the three outputs?** Characters reversed flips the entire text back to front, so the last letter comes first. Word order reversed keeps each word intact but reverses their sequence. Each word's letters reversed keeps the words in their original order but spells every word backwards.

**Does it work with emoji and accented characters?** Mostly, yes. Emoji are treated as single symbols rather than being split apart, and precomposed accented letters like e with an acute accent reverse cleanly. Text that uses separate combining accent marks can end up with the accent on the wrong letter, which is a limitation of how those characters are stored.

**How do I check whether a phrase is a palindrome?** Type it in and compare the characters reversed output with the original. Bear in mind that palindromes are normally judged ignoring spaces, punctuation and capitals, so never odd or even counts as a palindrome even though the reversed output keeps the spaces where they now fall.

**Why would anyone reverse text?** Puzzles and word games, mirror writing challenges, quirky social media bios, checking palindromes, and testing how software handles unusual strings. Teachers also use reversed text for spelling and decoding exercises.

**Is my text uploaded anywhere?** No. All three outputs are produced by JavaScript running in your browser. Nothing you type or paste leaves your device, and refreshing the page clears it.

### Small text generator
https://hopi.co.uk/small-text-generator/

Free small text generator. Turn normal letters into tiny superscript, small caps or fullwidth unicode text for bios and posts, with one-click copy per style.

**Why does the letter q stay normal in superscript?** Unicode has no superscript q. The superscript letters come from phonetic notation blocks that were never designed as a full alphabet, and q was simply never added. This tool leaves q unchanged rather than substituting a lookalike, and small caps has the same gap for x.

**Is this a font?** No. Fonts cannot travel inside plain text, so the tool swaps your letters for different unicode characters that happen to look small. Because they are real characters, they survive copying and pasting into places that never let you choose a font, such as social media bios and usernames.

**Will small text display everywhere?** On most modern phones, browsers and apps, yes. Some fonts are missing the rarer characters, in which case readers see empty boxes or question marks instead. If it looks right when you paste it into the app you are targeting, it will look right to others on similar devices.

**Does small text cause problems for screen readers?** It can. Screen readers often announce these characters letter by letter, with odd phonetic names, or skip them entirely, so text that looks fine visually can be gibberish or silence for a blind user. Use it for decoration only, never for information people need.

**Can I use small text in Instagram or X bios?** Yes, that is the most common use. The characters paste in like any other text. Be aware that some platforms count unusual characters as more than one character towards length limits, fullwidth ones especially, so check the counter before you save.

### Special characters to copy
https://hopi.co.uk/special-characters/

Free special character picker. Tap to copy arrows, stars, hearts, maths symbols, currency signs, dashes, quotes, legal marks and accented letters in one click.

**How do I copy a character?** Click or tap it. The button briefly shows Copied and the character is on your clipboard, ready to paste anywhere with ctrl+V, cmd+V or a long press on a phone. Copying happens locally in your browser.

**Why do some characters show as empty boxes?** Your device's fonts do not include a shape for that character. The character itself is still valid, and it will usually copy and paste correctly, but anyone whose fonts also lack it will see the same box. The common sets on this page display fine on almost all modern devices.

**What is the difference between the three dashes?** The hyphen on your keyboard joins words, as in well-known. The en dash is slightly longer and marks ranges, like pages 10 to 20 written with a dash. The em dash is the longest and is used by some styles to punctuate asides in a sentence. Publishers care about the difference even though they look similar.

**How do I type accented letters without this page?** On a Mac, hold the letter key and pick the accent from the popup. On Windows, the touch keyboard offers the same long-press, or use alt codes on the numeric keypad, such as alt 0233 for e with an acute accent. On phones, long-press the letter. Copying from here is simply quicker when you only need one.

**Is anything I copy tracked or uploaded?** No. The page is a static list of characters and the copying uses your browser's clipboard directly, so nothing you click is sent anywhere or recorded.

### Text repeater
https://hopi.co.uk/text-repeater/

Free text repeater. Repeat any word, line or phrase up to 10,000 times with your choice of separator and optional numbering. Runs in your browser.

**What is a text repeater useful for?** It saves you copying and pasting the same thing over and over. People use it to fill forms and databases with test content, to make placeholder text of an exact length, to build repetitive lists or spacing, and for the fun of sending the same word many times. Choose a separator and, if you want, number each copy.

**How do the separator options work?** The separator is the text placed between each copy, not before the first or after the last. None joins the copies with nothing at all, space puts a single space between them, new line puts each copy on its own line, and comma separates them with a comma and a space. Custom lets you type your own, such as a dash or a bullet.

**What does the numbering checkbox do?** When ticked it adds a number and a full stop in front of each copy, so the third copy of ok becomes 3. ok. Combined with the new line separator this gives you a tidy numbered list. Leave it unticked for a plain repeat with no numbers.

**Why did my output stop before all the copies?** The output is capped at 100,000 characters to keep the page fast and responsive. If your text and count would go past that, the tool stops at the cap and tells you in the note under the output. Use a shorter piece of text or a smaller count to fit more copies in.

**Is my text uploaded anywhere?** No. The repeating happens in your browser and the text never leaves your device. Refreshing the page clears everything.

### Text splitter
https://hopi.co.uk/text-splitter/

Free text splitter. Break long text into chunks without cutting words, add 1/4 thread numbering, or split at a delimiter. Copy each block in one click.

**What does word-boundary aware mean?** Blocks are cut at spaces, tabs or line breaks rather than mid-word. A word that would push a block over the limit moves to the start of the next block instead. The only exception is a single unbroken run longer than the limit itself, such as a very long URL, which has to be cut hard.

**Does the thread numbering count towards the character limit?** Yes, and the tool allows for it. When numbering is on, each block is split slightly shorter so that the suffix, such as 2/4, still fits inside your limit. That is why numbered blocks come out a few characters shorter than the limit you set.

**How do I split at line breaks or tabs?** In delimiter mode, type \n in the delimiter box for a line break or \t for a tab. Any other text works literally, so --- splits wherever three hyphens appear. Blocks that end up empty after trimming are dropped.

**What limit should I use for a thread on X?** Posts are capped at 280 characters for most accounts, which is why 280 is the default. Note that X counts every link as 23 characters regardless of its real length, so a block containing a long URL may fit even if the raw character count says otherwise.

**Is my text uploaded anywhere?** No. The splitting happens in your browser using JavaScript, and nothing you paste leaves your device.

### Upside down text
https://hopi.co.uk/upside-down-text/

Free upside down text generator. Flip words and sentences upside down using unicode lookalike characters, then copy and paste the result anywhere.

**Is this a font or a filter?** Neither. The tool swaps each letter for a different unicode character that happens to look like the original turned through 180 degrees, then reverses the order so the whole line reads correctly when flipped. Because they are real characters, they survive copying and pasting into places that never let you choose a font.

**Why do some letters look slightly wrong?** Unicode was never designed for this. The flipped shapes are borrowed from phonetic alphabets, mathematical notation and other scripts, so letters like B, Q and K only have rough stand-ins. The result is a good visual approximation rather than a perfect rotation, and a few characters will always look a little off.

**Will upside down text work in bios and messages?** Usually, yes. Most modern phones and browsers display the characters fine, which is why it is popular in social bios and usernames. Devices with older or limited fonts may show empty boxes for the rarer characters, so check how it looks in the app you are targeting.

**Does it cause problems for screen readers?** It can. Screen readers announce these characters by their real names, often letter by letter from phonetic alphabets, so flipped text can be read out as gibberish or skipped entirely. Treat it as decoration and never use it for information someone actually needs.

**Is my text uploaded anywhere?** No. The flipping is a simple character swap that runs in your browser, and nothing you type leaves your device.

### Word counter
https://hopi.co.uk/word-counter/

Free word counter. Paste your text to count words, characters (with and without spaces), sentences, paragraphs and reading time instantly. Nothing is uploaded.

**How are words counted?** Any run of characters separated by spaces, tabs or line breaks counts as one word, which is the same rule word processors use. Hyphenated words like mother-in-law count as one word; numbers and email addresses count as words too.

**Is my text stored or uploaded anywhere?** No. The counting happens entirely in your browser using JavaScript. Nothing you type or paste ever leaves your device, and refreshing the page clears it.

**How long is a UCAS personal statement allowed to be?** The UCAS limit is 4,000 characters including spaces (or 47 lines, whichever comes first). Character count with spaces is the number to watch, which this tool shows live.

**What are the character limits on social media?** X (Twitter) allows 280 characters for standard accounts, Instagram captions allow 2,200, LinkedIn posts allow 3,000, and Facebook posts allow more than 60,000. Meta descriptions for search results are best kept to about 155 characters.

**How is reading time worked out?** The tool divides your word count by 225 words per minute, an average adult silent-reading speed. For reading aloud, such as a speech or presentation, budget around 130 words per minute instead.

### Word frequency counter
https://hopi.co.uk/word-frequency-counter/

Free word frequency counter. Paste text to see your most used words with counts and percentages, with an option to hide common words. Nothing is uploaded.

**How are words counted?** The tool lowercases your text and treats any run of letters, digits and apostrophes as a word, so don't counts once as one word and London and london count as the same word. Punctuation is stripped, and hyphenated words are counted as their separate parts.

**What are stopwords?** Stopwords are very common function words such as the, and, of, to, in and that. They dominate almost any frequency list without telling you anything about the text, so ticking the box removes about 50 of them from the results and lets the meaningful words rise to the top.

**How is the percentage worked out?** Each word's count is divided by the total number of words in the text and multiplied by 100. The percentage is always based on all words, so it stays the same whether or not stopwords are hidden from the list.

**What is this useful for?** Spotting overused words in essays and novels, checking keyword frequency on a web page, trimming repetition from cover letters and speeches, and analysing survey answers or reviews to see which words come up most.

**Is my text uploaded anywhere?** No. The counting happens entirely in your browser using JavaScript. Nothing you paste leaves your device, and refreshing the page clears it.

## Colour & design

### CMYK to RGB converter
https://hopi.co.uk/cmyk-to-rgb/

Free CMYK to RGB converter. Turn print colour values into RGB and hex instantly, convert back the other way, and preview the colour as you type.

**What is CMYK?** CMYK stands for cyan, magenta, yellow and key, which is the printing name for black. They are the four ink colours used in most colour printing, each given as a percentage from 0 to 100. Unlike a screen, which adds light, inks subtract light from white paper, so CMYK is called a subtractive colour model.

**What formula does this converter use?** It uses the standard device-independent formula: R = 255 multiplied by (1 minus C) multiplied by (1 minus K), with the same pattern for green from magenta and blue from yellow, where each ink value is a fraction from 0 to 1. It is the common quick conversion used by design tools for previews.

**How does the RGB to CMYK direction work?** First K is found as 1 minus the largest of R, G and B divided by 255. Then each ink is the leftover after black is removed, for example C = (1 minus R divided by 255 minus K) divided by (1 minus K). If the colour is pure black, C, M and Y are all set to 0 and K to 100.

**Why does my printed colour not match the screen preview?** Because there is no single real-world CMYK. The printed result depends on the ink set, the paper and the press profile, and your screen has its own colour profile too. This converter uses the simple mathematical relationship, which is great for previews but not a substitute for proofing with your printer's ICC profile.

**Why is there a separate black ink at all?** In theory full cyan, magenta and yellow make black, but in practice they make a muddy dark brown and soak the paper with three layers of ink. A dedicated black ink is cheaper, dries faster and keeps small text sharp, which is why it does most of the work in dark areas.

### CSS gradient generator
https://hopi.co.uk/css-gradient-generator/

Free CSS gradient generator. Choose two colours, set the angle, switch between linear and radial, and copy ready-to-use CSS from the live preview.

**What does the angle mean?** The angle sets the direction the gradient travels. 0deg runs from bottom to top, 90deg from left to right, 180deg from top to bottom, and 270deg from right to left. Values in between tilt it: 135deg runs from the top left towards the bottom right.

**What is the difference between linear and radial?** A linear gradient blends the colours along a straight line at your chosen angle. A radial gradient starts with the first colour at the centre and blends outwards to the second colour at the edges, so it has no angle.

**Can I use more than two colours?** Yes. CSS gradients accept any number of comma-separated colour stops, so you can copy the generated code and add extra colours in the middle, optionally with percentage positions like #FF512F 30% to control where each stop sits.

**Why does my gradient show visible bands?** Banding appears when two colours are far apart in lightness and the blend is stretched over a large area, because screens can only show so many in-between shades. Choosing colours closer together, shortening the gradient or adding an intermediate colour stop all help.

**Do all browsers support these gradients?** Yes. Unprefixed linear-gradient and radial-gradient have worked in every major browser since around 2013, including Chrome, Firefox, Safari and Edge, so no vendor prefixes or fallbacks are needed for modern audiences.

### Colour name finder
https://hopi.co.uk/colour-name-finder/

Free colour name finder. Paste any hex code to find the exact or nearest of the 148 named CSS colours, with side by side swatches to compare them.

**Where do the 148 colour names come from?** Most date back to the X11 window system of the 1980s, whose colour list was adopted by SVG and then by CSS as the extended colour keywords. The newest, rebeccapurple, was added in 2014 in memory of Rebecca Meyer, the daughter of CSS pioneer Eric Meyer. All 148 work in every modern browser.

**How is the closest colour chosen?** Your colour and every named colour are compared as points in RGB space, using the straight-line distance across the red, green and blue channels. The name with the smallest distance wins. A distance of 0 is an exact match, and the bigger the number, the rougher the approximation.

**Can I use these names directly in CSS?** Yes. Every name here is a valid CSS colour value, so color: tomato or background: rebeccapurple works in any stylesheet, case-insensitively. Names are handy for prototypes and examples, though production code usually sticks to hex or custom properties for consistency.

**Why do some colours have two names?** The list contains spelling pairs like gray and grey, and historical duplicates like aqua and cyan, or fuchsia and magenta, which point to identical hex values. When your colour lands on one of these, this tool shows all the names that share the value, and any of them will work in CSS.

**Why does the closest name sometimes look quite different?** There are 16,777,216 possible six-digit hex colours and only 148 names, so each name has to cover a large neighbourhood. The names are also spread unevenly, with crowds of pale pastels and few mid greens, and plain RGB distance does not perfectly match human perception. Treat the result as the nearest label, not a twin.

### Colour palette from image
https://hopi.co.uk/image-palette/

Free palette extractor. Upload any photo and get its six dominant colours as clickable hex swatches, worked out in your browser. Nothing is uploaded anywhere.

**Is my photo uploaded anywhere?** No. The image is drawn onto an invisible canvas and analysed by JavaScript on your own device. It never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**How does the tool choose the colours?** It shrinks the image down, groups every pixel into a grid of similar colour bins, and ranks the bins by how many pixels landed in each. The top bins become the palette, with a minimum distance rule so you get six genuinely different colours rather than six near-identical shades of the largest area.

**Why is a colour I can see in the photo missing?** The palette favours colours that cover the most area. A small but eye-catching detail, like a red jacket in a landscape, may lose out to large stretches of sky or grass. To grab a specific pixel exactly, use the image colour picker instead.

**Why do the swatches look slightly different from the photo?** Each swatch is the average of all the pixels in its bin, so a textured area of many similar shades becomes one representative colour. That is usually what you want for design work, but it means a swatch may not match any single pixel precisely.

**What can I do with the palette?** Click any swatch to copy its hex code, then use it anywhere that accepts colours: CSS, Canva, PowerPoint or a brand document. The contrast checker will tell you whether two of the colours work as text and background, and the shades generator can build lighter and darker steps from any of them.

### Colour palette generator
https://hopi.co.uk/colour-palette-generator/

Free colour palette generator. Pick a base colour and generate five-swatch palettes using analogous, complementary and triadic schemes. Click to copy.

**How are the palettes generated?** Your base colour is converted to HSL, and the other swatches are made by rotating the hue around the colour wheel and adjusting lightness. Analogous palettes use neighbouring hues, complementary palettes use the hue directly opposite, and triadic palettes use three hues spaced 120 degrees apart.

**Which scheme should I choose?** Analogous palettes are calm and harmonious, good for backgrounds and interfaces. Complementary palettes have the most contrast and energy, good when you need one colour to pop against another. Triadic palettes are balanced but lively, and mixed borrows a little from each.

**Why do the swatches change slightly each time I press generate?** The generator adds a small random variation to the saturation and lightness of the supporting swatches, so pressing generate again gives you a fresh take on the same scheme. Your base colour itself is never altered.

**How do I actually use a five-colour palette?** A common approach is the 60-30-10 rule: one dominant colour for about 60% of the design, a supporting colour for 30%, and an accent for the remaining 10%. The two extra swatches cover backgrounds and text. Check text and background pairs with a contrast checker before shipping.

**Why does a grey base colour give a grey palette?** Greys have zero saturation, and a hue rotation only changes the hue, which is invisible when saturation is zero. Nudge your base colour towards an actual hue first, even slightly, and the schemes will start to show their character.

### Colour picker
https://hopi.co.uk/colour-picker/

Free online colour picker. Choose any colour with a visual picker and get its hex, RGB and HSL values instantly, each with a one-click copy button.

**How does the colour picker work?** Click the large colour swatch and your browser opens its native picker, with a spectrum, sliders and often an eyedropper. As you choose, the tool converts the selection to hex, RGB and HSL and shows all three with copy buttons.

**What is the difference between hex, RGB and HSL?** They are three ways of writing the same colour. Hex packs the red, green and blue values into six base-16 digits, RGB lists them in decimal from 0 to 255, and HSL describes the colour as hue, saturation and lightness, which is easier for humans to adjust.

**Can I pick a colour from an image or a website?** In Chrome and Edge the native picker includes an eyedropper that can sample anything on screen. For images there is a dedicated image colour picker on this site: upload a photo and click any pixel to read its colour.

**Why does the same hex code look different on another screen?** A hex code is an instruction, not a guarantee. Every screen has its own brightness, colour temperature and calibration, so the light it actually emits varies. For colour-critical work designers use calibrated monitors, but for the web the code is the shared truth.

**Can I pick a transparent colour?** The native picker returns solid colours only. To add transparency, take the RGB values and use the rgba() form, for example rgba(31, 138, 112, 0.5) for 50% opacity, or append an alpha pair to the hex code, where 80 is roughly 50%.

### Contrast checker
https://hopi.co.uk/contrast-checker/

Free WCAG contrast checker. Pick text and background colours to get the exact contrast ratio with instant pass or fail results for AA and AAA.

**What contrast ratio does my text need?** For WCAG level AA, normal text needs at least 4.5:1 and large text needs at least 3:1. For the stricter AAA level, the targets rise to 7:1 for normal text and 4.5:1 for large text. Ratios run from 1:1 (identical colours) to 21:1 (black on white).

**What counts as large text?** Text of at least 18 point, which is about 24 CSS pixels, or bold text of at least 14 point, about 18.5 pixels. Everything smaller is normal text and needs the higher ratio. Headings often qualify as large; body copy almost never does.

**What is the difference between AA and AAA?** They are conformance levels in the Web Content Accessibility Guidelines. AA is the level most organisations aim for and the one usually referenced in accessibility regulations. AAA is stricter and helps more people, particularly those with low vision, but is not always achievable across an entire site.

**Why does my light grey text keep failing?** Because its luminance is too close to a white background. On pure white, #767676 is the lightest grey that still reaches 4.5:1, and popular greys like #999999 fall well short. Darkening the text a little usually fixes it without changing the design's character.

**Does contrast only apply to text?** No. WCAG also requires a ratio of at least 3:1 for user interface components and meaningful graphics at level AA, covering things like input borders, icons and chart lines. Purely decorative elements and disabled controls are exempt.

### HSL converter
https://hopi.co.uk/hsl-converter/

Free HSL converter. Turn any hex code into hue, saturation and lightness, or mix a colour with H, S and L sliders and get the hex and RGB values.

**What do the three HSL numbers mean?** Hue is a position on the colour wheel from 0 to 360 degrees, where 0 is red, 120 is green and 240 is blue. Saturation runs from 0% (grey) to 100% (fully vivid). Lightness runs from 0% (black) through 50% (the pure colour) to 100% (white).

**Why use HSL instead of hex or RGB?** Because it matches how people think about colour. To darken a colour you lower lightness and leave the hue alone, and to soften it you lower saturation. Doing the same in hex or RGB means juggling three numbers at once and usually drifting off hue.

**Is HSL the same as HSV or HSB?** No, although they are related. HSV (also called HSB) uses value instead of lightness, and the scales behave differently at the top. In HSL, 100% lightness is always white. In HSV, 100% value is the fully bright version of the colour, not white.

**Why does a grey colour show a hue of 0?** Greys, including black and white, have no hue at all because their red, green and blue channels are equal. When saturation is 0% the hue number makes no difference to the colour, so converters report it as 0 by convention.

**Does converting between hex and HSL lose accuracy?** Slightly, because HSL values are usually rounded to whole degrees and whole percentages. Converting back can land a point or two away in RGB terms, which is invisible in practice. For exact brand colours, record the hex code as the master value.

### Hex to RGB converter
https://hopi.co.uk/hex-to-rgb/

Free hex to RGB converter. Enter any hex colour code to get its RGB and HSL values instantly, with a live colour preview and one-click copy.

**What is a hex colour code?** A hex code is a six-character code describing a colour as three pairs: red, green and blue. Each pair is a hexadecimal (base-16) number from 00 to FF, which is 0 to 255 in decimal. So #D7263D means red 215, green 38, blue 61.

**How do I convert hex to RGB by hand?** Split the code into pairs and convert each pair from base 16. Multiply the first digit by 16 and add the second, where A to F stand for 10 to 15. For example D7 is 13 × 16 + 7 = 215.

**What do three-digit hex codes like #F0C mean?** They are shorthand where each digit is doubled. #F0C expands to #FF00CC. This tool accepts both three and six digit codes.

**When should I use hex and when RGB?** They describe exactly the same colours, so it is mostly convention. Hex is compact and common in CSS and design tools. The rgb() form is easier to read and to manipulate in code, and rgba() adds an opacity channel.

**What about hex codes with eight digits?** An eight-digit code like #D7263D80 includes a fourth pair for alpha (opacity), where 00 is fully transparent and FF is fully opaque. 80 is about 50% opacity. The first six digits convert exactly as normal.

### Image colour picker
https://hopi.co.uk/image-colour-picker/

Free image colour picker. Upload a photo and click any pixel to get its hex and RGB values, with recent picks saved. Everything stays on your device.

**Is my photo uploaded anywhere?** No. The image is opened and read entirely in your browser using the canvas element, and it never leaves your device. You can load the page, disconnect from the internet and the picker still works.

**Which image formats can I use?** Anything your browser can display: JPG, PNG, WebP, GIF, AVIF and SVG all work in modern browsers. If a format fails to load you will see an error message rather than a blank canvas.

**Why is the picked colour slightly different from what I expected?** JPEG compression shifts pixel values subtly, and edges in any image are anti-aliased, meaning pixels there are a blend of the two sides. Pick from a flat area away from edges, and take two or three samples to check they agree.

**Why does the image appear smaller than the original?** Very large images are scaled down to a maximum of 1600 pixels wide so the page stays fast. Scaling averages neighbouring pixels, which can smooth tiny details, but colours in flat areas are unaffected.

**How do I pick a colour from a website rather than a photo?** Take a screenshot and drop it into this tool, or use the eyedropper built into the native colour picker in Chrome and Edge, which can sample anything visible on screen.

### RGB to hex converter
https://hopi.co.uk/rgb-to-hex/

Free RGB to hex converter. Enter red, green and blue values from 0 to 255 to get the hex colour code instantly, with a live preview and one-click copy.

**How do I convert RGB to hex by hand?** Divide each value by 16. The whole-number part is the first character and the remainder is the second, with 10 to 15 written as A to F. So 215 is 13 remainder 7, which gives D7. Join the three pairs in red, green, blue order and add a # at the front.

**Why do hex codes contain letters?** Hexadecimal is base 16, so it needs sixteen digits rather than ten. After 0 to 9 it borrows the letters A to F to stand for 10 to 15. That lets any value from 0 to 255 fit in exactly two characters.

**Does it matter if a hex code is uppercase or lowercase?** No. Browsers and design tools treat #d7263d and #D7263D as exactly the same colour. Uppercase is common in brand guidelines and lowercase is common in CSS style guides, so pick one and be consistent. This tool outputs uppercase.

**Why do RGB values stop at 255?** Each channel is stored in one byte, which is 8 bits, and 8 bits can hold 256 different values: 0 to 255. That is also why a channel always fits in a two-character hex pair, because FF in base 16 is 255.

**What if my RGB values are decimals between 0 and 1?** Some tools, including shaders and certain design plugins, use a 0 to 1 scale instead of 0 to 255. Multiply each value by 255 and round to the nearest whole number first. For example 0.5 becomes 128 and 1.0 becomes 255.

### Random colour generator
https://hopi.co.uk/random-colour-generator/

Free random colour generator. Click once for a truly random colour with its hex, RGB and HSL values, a full preview and a history of recent picks.

**How random are the colours?** As random as your device can make them. The tool uses the browser's cryptographic random number generator, the same source used for encryption keys, rather than the weaker Math.random. Each of the three channels gets an independent, unbiased value from 0 to 255.

**How many different colours can it produce?** 16,777,216, which is every colour a standard screen can show. Each of the red, green and blue channels has 256 possible values, and 256 × 256 × 256 = 16,777,216.

**Can the same colour come up twice?** Yes, though not often. The chance of two consecutive clicks matching is 1 in 16,777,216. Over a long session repeats somewhere in your history become likely much sooner, at around 4,800 draws, the same birthday effect that makes shared birthdays common in small groups.

**Is anything sent to a server?** No. The colours are generated by JavaScript running in your browser and never leave your device. Nothing is logged or stored, and refreshing the page clears the history.

**What are random colours actually useful for?** Breaking design fixation, mostly. A random starting point forces you out of the five colours you always reach for, and one nudge in HSL usually turns a wild pick into something usable. They are also handy as placeholders, for telling debug elements apart and for games.

### Shades & tints generator
https://hopi.co.uk/colour-shades-generator/

Free shades and tints generator. Pick any base colour and get five lighter tints and five darker shades, each a click away from a copied hex code.

**What is the difference between a tint and a shade?** A tint is your colour mixed with white, so it gets lighter. A shade is your colour mixed with black, so it gets darker. There is a third term, tone, for a colour mixed with grey, which mutes it without much changing how light it is.

**How are the tints and shades calculated?** Each red, green and blue channel is moved towards 255 for tints or towards 0 for shades, in five equal steps of one sixth. That gives mixes of roughly 17%, 33%, 50%, 67% and 83%, so the last swatch in each row is close to white or black but never quite reaches it.

**Why do my tints look washed out?** Mixing white into a colour lowers its saturation as well as raising its lightness, so strong brand colours can turn pastel quickly. That is often exactly what you want for backgrounds. If you need a lighter colour that keeps its intensity, try raising lightness in HSL instead and nudging saturation back up.

**What are shades and tints actually used for?** They are the workhorses of interface design. Tints make hover states, selected rows, subtle backgrounds and disabled states, while shades make borders, pressed buttons and text that sits on the tinted versions. Using steps of one colour keeps a design coherent instead of introducing new hues.

**Why does black only produce grey swatches?** Tints of black are simply greys, because mixing white into pure black raises all three channels equally. The same happens in reverse with white, whose shades are the same greys. Every neutral grey behaves this way, since there is no hue to preserve.

## Date & time

### Add working days
https://hopi.co.uk/add-working-days/

Free add working days calculator. Add or subtract working days from any date, skipping weekends and England and Wales bank holidays, to find a deadline date.

**Does the start date count as day one?** No. Counting starts from the next working day, matching how deadlines are set: ten working days from today means today plus ten more working days, not nine. So the start date itself is never the answer unless you enter zero working days.

**Which bank holidays does it skip?** With the box ticked, the eight England and Wales bank holidays in each of 2026 and 2027, using the official gov.uk dates including substitute days. For dates outside those two years the calculator skips weekends only, and tells you so under the result.

**What is a working day here?** Monday to Friday. Saturdays and Sundays are always skipped, and bank holidays are skipped too when the box is ticked. If you work a different pattern, such as weekends or fixed part-time days, treat the result as a Monday to Friday baseline and adjust.

**Can I count backwards from a date?** Yes. Choose Subtract and the tool counts working days before the start date instead of after it. That is handy for questions like when notice must be served so that a deadline lands on a specific day.

**Does it work for Scotland and Northern Ireland?** The weekend logic works everywhere, but the bank holiday list is the England and Wales one. Scotland has 2 January and St Andrew's Day, and Northern Ireland adds St Patrick's Day and the Twelfth of July, so adjust the result by a day or two if those apply to you.

### Age calculator
https://hopi.co.uk/age-calculator/

Free age calculator. Enter a date of birth to see exact age in years, months and days, total days lived, and how long until the next birthday.

**How is exact age calculated?** The calculator counts complete years first, then complete months since the last birthday, then the days left over, borrowing from the previous month's actual length where needed. That is why the answer is precise even though months vary between 28 and 31 days.

**What about people born on 29 February?** A leap-day birthday only occurs every four years. In non-leap years this calculator (like UK law for age milestones) treats 1 March as the day the age ticks over.

**Can I work out age at a date other than today?** Yes. Change the second date to any date you like, past or future, and the tool shows the age on that date. This is handy for forms that ask for age on a given cut-off date, such as school admissions or race categories.

**How many days old am I?** The total days figure counts every day between the date of birth and the chosen date, including leap days. Someone exactly 30 years old has lived roughly 10,957 days.

**Is my date of birth stored?** No. The calculation runs entirely in your browser and nothing is sent to any server. Refreshing the page clears the dates.

### Cat age calculator
https://hopi.co.uk/cat-age-calculator/

Free cat age calculator. Convert cat years to human years with the standard chart: 15 for the first year, 9 for the second, then 4 human years per cat year.

**How do cat years work?** The standard chart counts a cat's first year as about 15 human years and the second as about 9 more, so a two year old cat is roughly 24. Every year after that adds about 4 human years. Cats mature extremely quickly at first, which is why a one year old cat is already the equivalent of a teenager, then age at a steady rate.

**How old is a 10 year old cat in human years?** About 56. Two years takes a cat to 24, and the remaining eight years add 8 times 4, which is 32 more. That places a 10 year old cat in the mature stage, the feline equivalent of a human in their late 40s and 50s.

**Do indoor and outdoor cats age differently?** The chart is the same, but the risks are not. Indoor cats in the UK commonly live to 15 or beyond, while cats with unsupervised outdoor access face traffic and other hazards that lower average lifespan. Outdoor time does not speed up ageing itself, it just adds dangers, so the human-age conversion applies equally to both.

**Does breed or size change the chart like it does for dogs?** Far less. Dogs range from 2 kg to 80 kg and their ageing rate varies hugely with size, but most cats are within a few kilograms of each other, so a single chart works for almost all of them. Some pedigree breeds have known health issues that affect lifespan, but the year-to-year conversion stays the same.

**When does a cat count as a senior?** Vets commonly describe cats of 7 to 10 as mature, 11 to 14 as senior and 15 plus as super senior, which in human terms is roughly 44 to 56, 60 to 72 and 76 upwards. Many practices recommend more frequent checkups from the mature stage onwards. This tool is a friendly approximation, not veterinary advice.

### Countdown to a date
https://hopi.co.uk/countdown-timer/

Free countdown timer. Pick any date and an optional time and watch a live countdown in days, hours, minutes and seconds, updating every single second.

**Do I have to enter a time?** No. Leave the time blank and the countdown targets midnight at the very start of your chosen date. Add a time if the moment matters, such as a 9am exam, a 3pm kick-off or a midday ticket release.

**What happens when the countdown reaches zero?** It rolls straight over into counting up, showing how long it has been since the moment passed. That makes it just as useful for anniversaries and time-since milestones as for events still to come.

**Does it keep counting if I close the page?** The target is a fixed moment in time, so nothing needs to keep running. When you come back and set the same date, the countdown is recalculated from your device clock and is exactly right. Nothing is stored or uploaded; everything happens in your browser.

**Which time zone does it use?** Your device's. The countdown targets the date and time as your own clock understands them, so if you are counting down to an event in another time zone, convert it to your local time first.

**Why does the days figure differ from the days between dates calculator?** That tool counts whole calendar days. A countdown measures the exact time remaining, so at 3pm on Monday a target of Wednesday midnight shows 1 day and 9 hours, not 2 days. Both are right; they answer slightly different questions.

### Date calculator
https://hopi.co.uk/date-calculator/

Free date calculator. Add or subtract days, weeks, months or years from any date and see the resulting date and weekday instantly.

**What happens when I add a month to the 31st?** If the target month is shorter, the calculator lands on its last day: 31 January plus one month gives 28 February (29 in a leap year). This clamping matches how contracts and subscriptions usually behave, and avoids silently rolling into March.

**How do I work out a deadline like 28 days from today?** Leave the start date as today, choose add, enter 28 and pick days. The result shows the exact date and its weekday, which matters when a deadline lands on a weekend.

**Does adding a year handle leap days?** Yes. One year after 29 February 2024 lands on 28 February 2025, the last day of the shorter month, and leap days within any range are counted correctly.

**Are weekends and bank holidays skipped?** No, this calculator moves through calendar days. If you need working days only (skipping weekends), count the equivalent weeks: 10 working days is 2 calendar weeks. A dedicated working days calculator is on its way.

**Why does the weekday of the result matter?** Returns windows, notice periods and visa limits all expire on a specific calendar day. Knowing it is a Sunday tells you to act by the Friday before, which is exactly the sort of catch this tool is for.

### Day of the week finder
https://hopi.co.uk/day-of-week-calculator/

Free day of the week finder. Discover the weekday for any date in history or the future, and see where that same date lands in the current year.

**Which day of the week was I born on?** Type your date of birth and the weekday appears instantly. The tool also shows which weekday that date falls on this year, handy for knowing your birthday's day of the week without opening a calendar.

**Why is my birthday on a different day each year?** A common year is 365 days, which is 52 weeks plus one day, so the same date moves forward one weekday a year. When a 29 February sits in between, it jumps two. That is why a Tuesday birthday one year is a Wednesday or Thursday the next.

**What if I was born on 29 February?** In leap years the tool shows the real weekday as normal. In other years there is no 29 February, so it tells you that and gives the weekday of 1 March instead. The next 29 February after 2026 is in 2028.

**How far back can I go?** The calculator accepts any date, but it applies today's Gregorian calendar all the way back. Britain used the Julian calendar until September 1752, when 11 days were skipped, so weekdays for earlier British dates may not match what contemporary documents say.

**Is there a trick to work out weekdays in your head?** Yes, the Doomsday rule. In any year, 4 April, 6 June, 8 August, 10 October and 12 December all share one weekday (Saturday in 2026), and you count to nearby dates from those anchors. This tool is quicker, but the rule is a great party trick.

### Days between dates calculator
https://hopi.co.uk/days-between-dates/

Free days between dates calculator. Count the days, weeks and weekdays between any two dates, with the option to include the end date.

**Is the end date included in the count?** By default no: Monday to Friday counts 4 days, the gaps between the dates. Tick include the end day to count Monday to Friday as 5 days, which is what you want for durations like hotel nights versus days of an event.

**What is the difference between days and weekdays?** Days counts every calendar day including weekends. Weekdays counts Monday to Friday only. Note that weekdays still includes bank holidays, since those vary by country and year.

**Why do people get off-by-one errors counting days?** Because counting the gap and counting the days are different questions. From the 1st to the 3rd is a gap of 2 days, but touches 3 calendar days. Decide which question you are asking, then set the include-the-end-day toggle to match.

**Can I count between dates years apart?** Yes. The calculator handles any range and accounts for leap years automatically, so the gap between dates decades apart is exact.

**How do I count working days excluding bank holidays?** The weekdays figure here excludes weekends only. For a count that also skips UK bank holidays, use a working days calculator, which is on its way to Hopi.

### Days until Christmas
https://hopi.co.uk/days-until-christmas/

Free days until Christmas countdown. See how many sleeps are left until 25 December, with live hours, minutes and seconds, rolling over automatically each year.

**What exactly is a sleep?** A sleep is one night between now and Christmas morning. On Christmas Eve there is 1 sleep left, and on Christmas Day itself there are none. It is the way most families count with children, because nights are easier to picture than 24-hour blocks.

**Why do the sleeps and the days figures sometimes differ?** Sleeps count whole nights, while the days figure measures exact elapsed time to midnight at the start of 25 December. At 9pm on 23 December there are 2 sleeps left but only 1 full day and 3 hours on the clock. Both are correct; they answer slightly different questions.

**Does it work after Christmas has passed?** Yes. Once Christmas Day is over, the countdown rolls over automatically and starts counting towards 25 December of the following year. You never need to change a setting, whatever the date.

**Which time zone does the countdown use?** Your device's own clock. Christmas arrives at midnight local time wherever you are, so the countdown always matches what your calendar says. Nothing is stored or uploaded; everything runs in your browser.

**How many sleeps until Christmas from 1 December?** 24 sleeps, which is exactly why advent calendars have 24 doors. Each door you open is one sleep crossed off, with the last opened on Christmas Eve.

### Dog age calculator
https://hopi.co.uk/dog-age-calculator/

Free dog age calculator. Convert dog years to human years with the veterinary chart: 15 for the first year, 9 for the second, then 4 to 6 a year by size.

**Is one dog year really seven human years?** No, that is a myth. Dogs mature far faster than that at first: a one year old dog is roughly like a 15 year old human, not a 7 year old. The rate then slows sharply, and from age two it depends on the dog's size. The times seven rule only ever worked as a very rough average across a whole lifetime.

**How does the chart actually work?** The standard veterinary chart counts the first year as about 15 human years and the second as about 9 more, so a two year old dog of any size is roughly 24. From then on each dog year adds about 4 human years for a small dog, 5 for a medium dog and 6 for a large one.

**What counts as small, medium or large?** As a rough guide, small is under about 10 kg (terriers, dachshunds, most toy breeds), medium is about 10 to 25 kg (spaniels, collies, most bulldogs) and large is over 25 kg (labradors, German shepherds, and anything bigger). The boundaries are fuzzy and giant breeds age faster still, so treat the size bands as approximate.

**What is the logarithmic formula I have heard about?** A 2020 study at the University of California San Diego compared chemical markers on dog and human DNA and proposed human age = 16 times the natural log of the dog's age, plus 31. It makes young dogs surprisingly old (a two year old maps to about 42) and elderly dogs converge slowly. It was based on labradors, so the classic chart remains the everyday tool.

**Is this accurate for my dog?** It is a friendly approximation, not a diagnosis. Breed, weight, genetics and lifestyle all shift the picture, and no formula captures an individual dog. Your vet's assessment of body condition, teeth, joints and bloodwork says far more about your dog's biological age than any chart. Nothing you enter here is stored or sent anywhere.

### Hours calculator
https://hopi.co.uk/hours-calculator/

Free hours calculator. Enter start and end times and any break to see hours worked as a decimal and in hours and minutes, including overnight shifts.

**How does the calculator handle overnight shifts?** If the end time is earlier than the start time, the calculator assumes the shift crosses midnight and adds 24 hours. So 22:00 to 06:00 counts as 8 hours, not minus 16. The shift length row is labelled overnight so you can see this has happened.

**Why does 7 hours 30 minutes show as 7.5 hours?** Decimal hours express the minutes as a fraction of an hour, so 30 minutes is 0.5 hours, not 0.30. Payroll systems use decimal hours because pay is hours multiplied by an hourly rate, and that multiplication only works with decimals.

**Are breaks paid in the UK?** Workers over 18 are entitled to an uninterrupted 20-minute rest break when working more than 6 hours, and by default it is unpaid. Many employers offer longer or paid breaks in the contract, so check yours before deciding what to subtract.

**How do I add up a whole week of shifts?** Work out each shift here, note the hours and minutes, then add them together with the time calculator. Keeping everything in hours and minutes until the final total avoids decimal rounding creeping in.

**Is anything I enter stored?** No. The calculation runs entirely in your browser and nothing is sent to any server. Refreshing the page resets the times.

### Leap year checker
https://hopi.co.uk/leap-year-checker/

Free leap year checker. Enter any year to see if it is a leap year, with the 4, 100 and 400 rules explained, plus the next and previous leap years.

**What makes a year a leap year?** A year is a leap year if it divides exactly by 4, unless it also divides by 100, in which case it must divide by 400 as well. So 2024 is a leap year, 1900 is not, and 2000 is. The extra day is always 29 February, making the year 366 days long instead of 365.

**Was 1900 a leap year?** No. It divides by 4, but it also divides by 100 and not by 400, so the century exception removes it. The year 2000 divides by 400, so it kept its leap day. This is the rule people most often get wrong, and spreadsheet software has famously got it wrong too: early Excel treats 1900 as a leap year for compatibility reasons.

**Why do we have leap years at all?** The Earth takes about 365.2422 days to orbit the Sun, not a neat 365. Without correction the calendar would drift by roughly a day every four years, and after a few centuries midsummer would fall in what the calendar called spring. Adding a day roughly every fourth year keeps the calendar locked to the seasons.

**Will 2100 be a leap year?** No. It divides by 4 and by 100 but not by 400, so the century rule skips it. The same applies to 2200 and 2300, while 2400 will be a leap year. Nobody alive today has experienced a skipped leap year, because 2000 happened to pass the 400 test.

**When did these rules start?** The 4, 100 and 400 system is the Gregorian calendar, introduced in 1582. Before that the Julian calendar made every fourth year a leap year with no exceptions. Britain and its colonies only switched in 1752, skipping 11 days in September to catch up, so results for very old years depend on which calendar you mean.

### Minutes to hours converter
https://hopi.co.uk/minutes-to-hours/

Free minutes to hours converter. Turn any number of minutes into hours and minutes or decimal hours for payroll and timesheets, then convert back instantly.

**How do I convert minutes to decimal hours?** Divide the minutes by 60. So 45 minutes is 45 divided by 60, which is 0.75 hours, and 20 minutes is 0.33 hours once rounded to two decimal places. Decimal hours are what payroll systems and spreadsheets expect.

**Is 1.5 hours the same as 1 hour 30 minutes?** Yes. The .5 means half of an hour, which is 30 minutes, not 50. Reading decimal hours as if the digits after the point were minutes is the most common mistake with timesheets, and it always overstates the time.

**Why do payroll systems use decimal hours?** Because pay is hours multiplied by an hourly rate, and multiplication only works cleanly with a single decimal number. 7 hours 30 minutes at £12 an hour is 7.5 times 12, which is £90. Trying to multiply 7:30 as if it were a number gives nonsense, which is why timesheets ask you to convert first.

**What is 100 minutes in hours?** 100 minutes is 1 hour 40 minutes, because 100 is one lot of 60 plus 40 left over. As a decimal it is 100 divided by 60, which is about 1.67 hours.

**How do I convert decimal hours back to minutes?** Multiply by 60. So 0.75 hours is 45 minutes, and 7.4 hours is 444 minutes, which is 7 hours 24 minutes. The hours to minutes mode above does this for you, and you can put the whole and fractional parts in either box.

### Moon phase calculator
https://hopi.co.uk/moon-phase-calculator/

Free moon phase calculator. Enter any date to see the moon phase, illumination percentage, days since the new moon, and the next full and new moon dates.

**How accurate is the phase?** To within about a day. The calculator uses the average length of the lunar cycle, while the real moon runs slightly fast or slow because its orbit is elliptical. For naming the phase, planning a moonlit walk or checking a photo date that is plenty; for eclipse timing you would want a full astronomical ephemeris.

**Is the moon phase the same everywhere in the world?** Essentially yes. The whole planet sees the same moon, so everyone shares the same phase at the same moment. The only difference is the calendar date: a full moon late in the evening in London can fall on the next calendar day in Auckland.

**What is a blue moon?** In popular use, a second full moon within one calendar month. Because the lunar cycle is about 29.5 days and most months are 30 or 31 days, it happens roughly every two to three years. The moon does not actually look blue.

**Why does the moon have phases at all?** Half of the moon is always lit by the sun. As the moon orbits the Earth roughly once a month, we see that lit half from changing angles, from none of it at new moon to all of it at full moon. The Earth's shadow is not involved, except during a lunar eclipse.

**Does the full moon affect sleep or behaviour?** Large studies have found no reliable effect on behaviour, and only small, disputed effects on sleep. The extra light of a bright full moon through thin curtains is the most plausible culprit for a restless night.

### Pomodoro timer
https://hopi.co.uk/pomodoro-timer/

Free Pomodoro timer with 25, 5 and 15 minute presets, custom lengths, session dots and an optional end beep. Stays accurate in background tabs.

**Why is a pomodoro 25 minutes?** There is nothing magical about the number. Francesco Cirillo, who invented the technique, simply used the tomato-shaped kitchen timer he had to hand. It has stuck because 25 minutes is short enough that starting feels easy and long enough to get something real done. Use the Custom option if another length suits you better.

**Does the timer stay accurate in a background tab?** Yes. It stores the exact finishing moment as a clock timestamp and works the remaining time out from that, rather than counting ticks. Browsers slow timers down in background tabs, but that only affects how often the display refreshes, never the moment the timer actually ends.

**Why did I not hear a beep?** The beep is off by default so the timer never surprises you. Tick the box to enable it, and do so before you press Start, because browsers only allow sound after you have interacted with the page. The countdown is also mirrored in the tab title, so you can spot the time remaining from another tab.

**What do the dots mean?** Each filled dot is a completed focus session in your current set of four. The classic pattern is a short break after each session and a longer break after every fourth, at which point the set starts again. Breaks do not fill dots, only focus sessions do.

**Can I run a session longer than 25 minutes?** Yes. Choose Custom and enter anything from 1 to 180 minutes. Plenty of people prefer 50 minute sessions with 10 minute breaks, which fit neatly into meeting-heavy calendars. The technique is a tool, not a rulebook.

### Star sign calculator
https://hopi.co.uk/star-sign-calculator/

Free star sign calculator. Enter any date of birth to find the matching western zodiac sign instantly, with date ranges for all 12 signs and cusps explained.

**I was born on a cusp, which sign am I?** A cusp is a birthday on or next to the boundary between two signs, such as 19 or 20 April. The Sun crosses each boundary at a precise moment that varies by a day or so from year to year, so people born on a boundary date can genuinely fall either side depending on their birth year and time. This calculator uses the most widely published fixed dates, which are right for the vast majority of birthdays.

**Why do some sites give slightly different dates for each sign?** Because the real boundary moves. The moment the Sun passes from one sign to the next shifts within a roughly one-day window across the four-year leap cycle, and it also depends on time zone. Different publishers freeze that moving target on slightly different calendar dates, which is why you will see Aries start on 20 or 21 March depending on where you look.

**What are the 12 star signs in order?** Starting from the spring equinox they run Aries, Taurus, Gemini, Cancer, Leo, Virgo, Libra, Scorpio, Sagittarius, Capricorn, Aquarius and Pisces. The cycle then starts again with Aries in late March.

**Is my star sign the same as the constellation the Sun was actually in?** Usually not. Western astrology uses the tropical zodiac, which is fixed to the seasons, but the Earth's slow wobble (precession) means the constellations have drifted by about one sign over the last two thousand years. Astronomers also point out the Sun passes through a thirteenth constellation, Ophiuchus. None of this changes your star sign, which is a calendar tradition rather than an astronomical measurement.

**Is my date of birth stored anywhere?** No. The lookup happens entirely in your browser and nothing is sent to any server. Refreshing the page clears the date.

### Stopwatch
https://hopi.co.uk/stopwatch/

Free online stopwatch with laps, showing split and total times to a hundredth of a second. Stays accurate even when the tab is in the background.

**How accurate is this stopwatch?** It uses your browser's high-resolution clock (performance.now), which measures in fractions of a millisecond, and the display shows hundredths of a second. In practice the limit is you, not the tool: human reaction time is around two tenths of a second, so any hand-operated stopwatch carries that margin on both the start and the stop.

**Does it keep time if I switch tabs?** Yes. The stopwatch records the moment you pressed Start and works the elapsed time out from that timestamp whenever it updates, rather than counting ticks. Browsers slow background tabs down, which can freeze the display, but the moment you come back the correct time is shown, including everything that passed while you were away.

**What is the difference between split and total?** Total is the time on the clock when you pressed Lap, measured from the very start. Split is how long that individual lap took, which is simply that lap's total minus the previous lap's total. Runners use splits to see whether each lap is faster or slower than the last.

**Is there a limit to how long it can run?** No practical one. The minutes column simply keeps growing, so an hour and a half shows as 90 minutes and change. If you close the tab the stopwatch stops, though, so for timing across days you may prefer noting start and end times and using the hours calculator.

**Are my times stored anywhere?** No. Everything runs in your browser and nothing is sent to any server. Refreshing or closing the page clears the clock and the lap list, so copy any times you want to keep before you leave.

### Time calculator
https://hopi.co.uk/time-calculator/

Free time calculator. Add or subtract two durations in hours and minutes and see the total in h:mm and decimal hours instantly, all in your browser.

**How do I add more than two durations?** Chain the results. Add the first two durations, then use the total as the first duration and add the next one, and so on. Because the tool works in whole minutes there is no rounding error when you chain, unlike adding decimal hours.

**What happens if I enter 90 minutes?** Minutes over 59 are perfectly fine. The calculator converts everything to minutes before doing the sum, so 1 hour 90 minutes is treated as 2 hours 30 minutes and the result is shown normalised.

**Can the result be negative?** Yes. If you subtract a longer duration from a shorter one the result is shown with a minus sign, for example -1:30. That is useful for working out how far behind a target you are.

**How do I turn decimal hours back into hours and minutes?** Keep the whole hours, then multiply the decimal part by 60. So 3.58 hours is 3 hours plus 0.58 times 60, which is about 35 minutes. This tool shows both formats so you rarely need to do it by hand.

**Why do timesheets use decimal hours?** Pay is hours multiplied by an hourly rate, and that multiplication needs a decimal. 7:30 must be entered as 7.5, because typing 7.30 would count only 18 minutes past the hour and underpay you by 12 minutes.

### Time zone converter
https://hopi.co.uk/time-zone-converter/

Free time zone converter. Convert any date and time between London, New York, Tokyo, Sydney and other major world zones, with daylight saving handled.

**Does the converter handle daylight saving time?** Yes. It uses your browser's built-in time zone database to find the UTC offset actually in force in each zone on the date you enter, so a London to New York conversion gives a 5 hour gap for most of the year and correctly drops to 4 hours for the couple of weeks in spring when the US has changed its clocks but the UK has not.

**What is the difference between UTC and GMT?** For everyday purposes they are the same time. UTC (Coordinated Universal Time) is the modern standard kept by atomic clocks, while GMT is the historical name and survives as the UK's winter time zone. In summer the UK is on BST, one hour ahead of UTC, so London time is only sometimes the same as UTC.

**Why are some zones offset by half an hour?** Offsets are political choices, not laws of nature. India uses UTC+05:30 as a single compromise zone for the whole country, Nepal uses UTC+05:45, and parts of Australia use half-hour offsets too. That is why the converter works in minutes rather than whole hours.

**What happens if I enter a time that does not exist?** When clocks go forward, one hour vanishes: in London the small hours of the last Sunday in March jump from 01:00 straight to 02:00. If you enter a time inside that gap the tool warns you and converts the time the clocks actually showed instead.

**Is anything sent to a server?** No. The conversion runs entirely in your browser using its built-in copy of the IANA time zone database, which is the same data operating systems use. Keeping your browser up to date keeps the daylight saving rules current.

### What week number is it?
https://hopi.co.uk/week-number/

Free week number finder. See the ISO 8601 week number for today or any other date, plus the Monday and Sunday of that week, instantly in your browser.

**Why does Excel give me a different week number?** Excel's WEEKNUM function defaults to the US system, where week 1 is whatever week contains 1 January and weeks start on Sunday. Use ISOWEEKNUM (or WEEKNUM with return type 21) to match this tool and the ISO 8601 standard used across the UK and Europe.

**How many weeks are there in 2026?** 2026 has 53 ISO weeks, which is the rarer case. A year gets 53 weeks when it starts on a Thursday, or when it is a leap year starting on a Wednesday. 2026 starts on Thursday 1 January, so week 53 runs right up to Sunday 3 January 2027.

**Can 1 January be in week 52 or 53?** Yes. ISO week 1 is the week containing the year's first Thursday, so up to three early January days can belong to the last week of the previous year. Friday 1 January 2027, for example, sits in week 53 of 2026.

**What is the ISO year and why does it matter?** It is the year the week belongs to, which can differ from the calendar year for dates between 29 December and 3 January. Payroll and planning systems that number weeks need it, otherwise week 1 versus week 53 becomes ambiguous at the year boundary.

**Does the week start on Monday or Sunday?** In ISO 8601, and in normal UK usage, the week runs Monday to Sunday, and that is what this tool shows. American calendars often start the week on Sunday, which is one reason week numbers from US software can disagree by one.

### Working days calculator
https://hopi.co.uk/working-days-calculator/

Free working days calculator. Count the working days between two dates, skipping weekends and England and Wales bank holidays for 2026 and 2027.

**Are both dates included in the count?** Yes. This calculator counts every working day from the start date to the end date inclusive, because that is how people plan work: Monday to Friday of the same week is 5 working days. If you want the gap between two dates instead, use the days between dates calculator.

**Which bank holidays does it exclude?** The eight England and Wales bank holidays in each of 2026 and 2027, using the official gov.uk dates including substitute days. For dates outside those two years the calculator excludes weekends only, and tells you so in the note under the result.

**Do Scotland and Northern Ireland have different bank holidays?** Yes. Scotland has 2 January and St Andrew's Day but not Easter Monday, and Northern Ireland adds St Patrick's Day and the Twelfth of July. This tool uses the England and Wales list, so adjust the result by a day or two if you are in Scotland or Northern Ireland.

**How many working days are there in 2026?** In England and Wales, 253. The year has 365 days and runs Thursday to Thursday, giving 261 weekdays, and all 8 bank holidays fall on weekdays, leaving 253 working days.

**What happens when a bank holiday falls on a weekend?** A substitute weekday is given instead, normally the following Monday. The lists used here already reflect that: for example Boxing Day 2026 is a Saturday, so the holiday moves to Monday 28 December 2026.

## Random & generators

### Barcode generator
https://hopi.co.uk/barcode-generator/

Free barcode generator. Make CODE128, EAN-13, EAN-8, UPC, CODE39 and ITF-14 barcodes in your browser and download them as a PNG or SVG. Nothing is uploaded.

**Which barcode format should I choose?** For a retail product going on a shelf, EAN-13 is the European standard and UPC-A is its North American cousin. EAN-8 suits very small packs. ITF-14 goes on shipping cartons. For anything internal, such as an asset tag or a reference number, Code 128 handles letters and numbers, and Code 39 is a simpler older alternative.

**Does this register a real product barcode?** No. The tool draws a barcode picture from whatever value you type, and nothing more. A barcode that a shop till will accept needs a GTIN number that you buy from GS1, the body that issues them. Once you have that number, you can paste it here to produce the image to print, but the number itself must come from GS1.

**Why does my number get rejected?** The retail formats have strict rules. EAN-13 needs 12 or 13 digits, EAN-8 needs 7 or 8, UPC-A needs 11 or 12, and ITF-14 needs an even count of 13 or 14 digits. If you type 12 digits for EAN-13 the tool adds the final check digit for you. Code 128 and Code 39 are far more relaxed about what they accept.

**What is the check digit?** It is the last digit of a retail barcode, calculated from the ones before it using a fixed sum. A scanner recomputes it and compares, which catches most misreads and typos. When you enter one digit short, this tool works out the correct check digit and appends it, so the barcode is always valid.

**Is my data uploaded anywhere?** No. The barcode is generated entirely in your browser and nothing is sent to a server, so it is safe to encode internal reference numbers, stock codes and anything else private. The PNG and SVG downloads are built on your device too.

### Bingo card generator
https://hopi.co.uk/bingo-card-generator/

Free UK 90-ball bingo card generator. Create 1 to 6 random cards with the classic 9 by 3 layout, 15 numbers each, then print them for your game night.

**What are the rules of a UK 90-ball bingo card?** Each card is a grid of 9 columns and 3 rows holding 15 numbers, with exactly 5 numbers in each row and the other 4 squares blank. The first column uses 1 to 9, the second 10 to 19 and so on up to 80 to 90 in the last, and numbers run in ascending order down each column. Every card here follows those rules.

**How do I call the numbers?** You need a way of drawing 1 to 90 in a random order with no repeats. Numbered balls or folded slips in a bowl work perfectly, and so does writing 1 to 90 on a sheet and crossing each number off as it is called. Whatever you use, keep a record of called numbers so wins can be checked.

**Can two cards share the same numbers?** They can share some, yes. Each card is generated independently, so the same number may appear on several cards, exactly like buying tickets from different bingo books. Within a single card no number ever repeats. Traditional printed strips of six tickets cover all 90 numbers with no repeats, which is a different format.

**How does printing work?** Press the print button and your browser's normal print dialogue opens with just the cards on the page, several to a sheet. Plain black and white is fine, and thicker paper survives a game night better. You can also save as PDF from the same dialogue to share cards by email.

**Is this the same as American bingo?** No. US bingo is usually 75-ball, played on a 5 by 5 card with the letters B-I-N-G-O over the columns and a free space in the middle. UK 90-ball bingo uses the 9 by 3 card this page generates, and is typically played for one line, two lines and then the full house.

### Bulk QR code generator
https://hopi.co.uk/bulk-qr-code-generator/

Free bulk QR code generator. Paste a list and get up to 1,000 QR codes as PNG, JPG or SVG in one ZIP, with a mapping.csv index. Nothing is uploaded.

**How do I choose my own filenames?** Put the name first, then a pipe character, then the text, like table-01 | https://example.com/menu. That line becomes table-01.png containing the link. Lines without a pipe are named automatically as qr-0001, qr-0002 and so on.

**What is mapping.csv for?** It is a two column index inside the ZIP listing every filename next to the exact text it encodes. A thousand QR images look identical to the eye, so the CSV is how you check, print or mail merge the right code against the right record. It opens in Excel or Google Sheets.

**Is my list uploaded anywhere?** No. The codes and the ZIP itself are built entirely in your browser with JavaScript, so lists of ticket links, serial numbers or internal URLs never leave your device. That also means there is no account, no watermark and no per-batch charge.

**Why did some lines fail?** Almost always because a line holds more text than one QR code can store, which is a hard limit of the QR specification. Failed lines are listed by line number and every other line still generates, so you can shorten the long ones and rerun just those.

**Which format should I pick?** PNG is the safe default for screens, documents and most print. JPG makes smaller files but has soft edges, so only use it where space is tight. SVG is a vector that stays perfectly sharp at any size, ideal for professional print work like labels and posters.

### Coin flip
https://hopi.co.uk/coin-flip/

Free online coin flip. Tap once for a fair heads or tails, with a running tally of your results. Uses cryptographic randomness, so every flip is a true 50/50.

**Is it a true 50/50?** Yes. Each flip draws on your browser's cryptographic random number generator (crypto.getRandomValues), so heads and tails are exactly equally likely. Studies of real coin tosses suggest a physical coin has a slight bias towards the side that starts facing up, so this is arguably fairer than the real thing.

**Why did I get several heads in a row?** Streaks are normal in genuinely random sequences. Five heads in a row has a 1 in 32 chance, so it will happen regularly if you keep flipping. Each flip is independent, and a streak says nothing about the next result.

**Does the tally affect the next flip?** No. The counts are just a record for you. Even if the tally shows 10 heads and 2 tails, the next flip is still exactly 50/50. Believing past results are owed a correction is known as the gambler's fallacy.

**Who calls heads or tails?** Convention says the person who did not suggest the toss makes the call, and they call while the coin is in the air. Online, agree who is heads before anyone presses the button, then flip once in front of both of you.

**Can I use it to settle a real decision?** Yes. The flip is fair, independent and cannot be influenced by either party. For anything contested, agree the terms first, press the button once with the other person watching, and accept the first result.

### Combination generator
https://hopi.co.uk/combination-generator/

Free combination generator. List every way of choosing r items from a set, see nCr and nPr counts instantly, and download the full list as a text file.

**What is the difference between combinations and permutations?** A combination ignores order: Alice and Ben is the same pair as Ben and Alice, so it is counted once. A permutation counts every ordering separately, so the same two people give two permutations. This tool lists combinations, and shows both counts so you can see how much bigger the permutation number is.

**Why is the list capped at 5,000 lines?** Combination counts explode astonishingly fast. Choosing 12 items from 25 already gives 5,200,300 combinations, which no browser should be asked to render. The tool always shows the exact total, calculated precisely however large it is, and lists the first 5,000 so you can inspect, copy or download them.

**Can I use numbers instead of typing a list?** Yes. Switch to number range mode and the tool uses the whole numbers 1 to n as the items. That is handy for lottery style questions, raffle tickets or picking seat numbers without typing anything out.

**What happens if my list contains duplicates?** Each line is treated as a separate item, even if two lines contain the same text. If you list Anna twice, combinations containing each copy are counted and listed separately. Remove duplicate lines first if that is not what you want.

**How large can n and r be?** The counts are calculated with exact whole-number arithmetic (BigInt), so even 1000 choose 500, a number with hundreds of digits, is computed exactly rather than overflowing or rounding. Only the rendered list is capped, at 5,000 lines.

### Dice roller
https://hopi.co.uk/dice-roller/

Free online dice roller. Roll up to 20 dice at once, choose d4, d6, d8, d10, d12 or d20, and see every result plus the total. Uses cryptographic randomness.

**Are the rolls fair?** Yes. Each roll uses your browser's cryptographic random number generator (crypto.getRandomValues) with rejection sampling, so every face of the die has an exactly equal chance. That is far stronger than the basic Math.random most tools rely on.

**What do d4, d6 and d20 mean?** The number after the d is the number of sides. A d6 is the familiar cube from board games, while d4, d8, d10, d12 and d20 are the dice used in tabletop role-playing games such as Dungeons and Dragons.

**Can I roll several dice at once?** Yes, up to 20 of the same type in one click. The tool lists every individual result and shows the total, the highest roll and the lowest roll underneath.

**Is a digital roll as good as a real die?** Often it is fairer. Cheap physical dice have rounded corners, uneven paint and air bubbles that skew results slightly, which is why casinos use precision-machined dice. A cryptographic roll has no physical imperfections at all.

**Why is there no d100?** You can make one easily: roll a d10 twice, use the first roll for tens and the second for units, and read a double zero as 100. Alternatively, use our random number generator set to 1 to 100.

### EuroMillions number generator
https://hopi.co.uk/euromillions-generator/

Free EuroMillions number generator. Fair random lines of 5 main numbers from 50 and 2 Lucky Stars from 12, using cryptographic randomness. Equal odds always.

**What is the EuroMillions format?** Each line is 5 main numbers chosen from 1 to 50 plus 2 Lucky Stars chosen from 1 to 12. Draws take place on Tuesday and Friday evenings, and in the UK a line costs £2.50. Matching all 5 main numbers and both Lucky Stars wins the jackpot.

**Do random numbers win more often?** No. Every possible line has an identical 1 in 139,838,160 chance of the jackpot, however it was chosen. The only practical difference is that random lines are less likely to duplicate other players' picks, so a winning random line would tend to share the prize with fewer people.

**Is this an official National Lottery tool?** No, it is an independent generator, the do-it-yourself equivalent of a Lucky Dip. It cannot buy tickets or check results, and your numbers never leave your device. To play for real you need an official ticket and must be 18 or over.

**What about the Millionaire Maker code?** Every EuroMillions line bought in the UK automatically comes with a Millionaire Maker raffle code, which guarantees at least one UK millionaire per draw. You do not choose that code, so no generator is involved; it is printed on your ticket when you buy.

**Can Lucky Stars repeat the main numbers?** The Lucky Stars are drawn from their own separate pool of 1 to 12, so a line can legitimately have, say, main number 7 and Lucky Star 7. Within each pool the numbers are always unique, exactly as the real draw works.

### Fortune cookie
https://hopi.co.uk/fortune-cookie/

Free online fortune cookie. Tap the cookie to crack it open and read one of 60 original fortunes, warm and witty, drawn fairly by cryptographic randomness.

**Where do the fortunes come from?** All 60 were written specially for this page. They are original, warm and family friendly, and you will not find the usual recycled lines about journeys of a thousand miles. No fortunes are fetched from anywhere: the whole list lives in the page and one is drawn at random each time.

**Can I get the same fortune twice?** Yes. Each cookie is an independent draw from 60 fortunes, so a repeat straight away has a 1 in 60 chance. Repeats become likely faster than you might expect: across ten cookies there is roughly a 55% chance of seeing at least one fortune twice.

**Are fortune cookies actually Chinese?** Not really. The best evidence points to Japan, where crackers with fortunes tucked into them were made in the 1800s. Japanese immigrants popularised them in California in the early 1900s, and they spread through Chinese-American restaurants. In China itself they are a curiosity, not a tradition.

**Is anything uploaded when I crack a cookie?** No. The fortune is chosen by your browser's own cryptographic random number generator and everything happens on your device. Nothing you do here is sent, stored or tracked, and refreshing the page simply bakes you a fresh cookie.

**Can I use these fortunes at my own event?** Yes, help yourself for personal use. They work nicely tucked into napkins or place cards at a dinner party, added to party bags, or read aloud at the end of a family meal. Keep cracking cookies until you have collected enough favourites.

### Lottery number generator
https://hopi.co.uk/lottery-number-generator/

Free lottery number generator for UK Lotto, Thunderball and Set For Life. Fair random lines using cryptographic randomness. Every combination has equal odds.

**Does a generator improve my chances of winning?** No, and any tool that claims otherwise is misleading you. Every possible line has exactly the same probability, whether you picked birthdays, patterns or random numbers. A random line has one small practical benefit: it is less likely to match other players' choices, so a jackpot would be shared with fewer people. It is no more likely to come up.

**Which games does this cover?** The three main National Lottery draw games: Lotto (6 numbers from 1 to 59), Thunderball (5 numbers from 1 to 39 plus a Thunderball from 1 to 14) and Set For Life (5 numbers from 1 to 47 plus a Life Ball from 1 to 10). For EuroMillions, use our separate EuroMillions generator.

**Is this connected to the National Lottery?** No. This is an independent random number tool, like a Lucky Dip you run yourself. It does not buy tickets, check results or send anything anywhere. To play you still need a ticket from an official National Lottery retailer or account, and you must be 18 or over.

**Can the same numbers appear twice?** Never within a line: each line contains unique main numbers, sorted low to high, exactly as a real entry requires. Separate lines are independent draws, so two lines could occasionally share numbers, just as two Lucky Dips can.

**How random is it really?** Numbers come from your browser's cryptographic random number generator with unbiased sampling, the same class of randomness used for encryption. That said, remember the honest truth: no source of randomness, however good, changes the odds of winning.

### Magic 8 ball
https://hopi.co.uk/magic-8-ball/

Free online magic 8 ball. Ask any yes or no question, shake the ball and get one of the 20 classic answers, chosen fairly by cryptographic randomness.

**What are the 20 classic answers?** The traditional set has 10 positive answers (It is certain, Signs point to yes and so on), 5 vague ones (Ask again later, Reply hazy, try again) and 5 negative ones (My reply is no, Very doubtful). This page uses that classic list unchanged, so half of all shakes come up positive.

**Is every answer equally likely?** Yes. Each shake uses your browser's cryptographic random number generator to pick one of the 20 answers, so every answer has exactly a 1 in 20 chance. The wobble animation is just for show and has no effect on the result.

**Why do I keep getting vague answers?** Five of the twenty answers are non-committal, so on average one shake in four tells you to ask again. Two vague answers in a row has a 1 in 16 chance, which is common enough to notice. Every shake is independent, so just shake again.

**Does my question affect the answer?** No. The question box is there to help you focus and to remind you what you asked. The text is never read, stored or uploaded, and the answer is chosen by pure chance regardless of what you type, or whether you type anything at all.

**Is this the official Magic 8 Ball toy?** No. Magic 8 Ball is a trademark of Mattel, and the physical toy uses a floating 20-sided die in blue liquid. This page is a free homage that reproduces the same 20 answers with fair randomness in your browser.

### Passphrase generator
https://hopi.co.uk/passphrase-generator/

Free passphrase generator. String three to eight random English words into a passphrase that is easy to remember and hard to crack. Made in your browser.

**Is a passphrase really safer than a normal password?** Safer than the passwords most people invent, yes. Human-made passwords lean on names, dates and keyboard patterns that attackers try first. A passphrase of randomly chosen words has no such patterns, and because it is easy to remember you can afford to make it long, which is what strength really comes from.

**How many words should I use?** Four words is fine for everyday accounts. Use six or more for anything important, such as a password manager master password, your email account or a wifi key. Each extra word from this list adds about 8 bits of entropy, roughly multiplying the guessing work by 250.

**Is my passphrase sent to a server?** No. The words are picked by JavaScript running on your own device, using your browser's cryptographic random number generator. Nothing is transmitted, logged or stored, and leaving the page destroys what was on screen.

**Why does the word list only have 250 words?** Short, common words are quick to type and easy to remember, which encourages you to use more of them. Strength comes from the number of words, not the obscurity of each one. If you want more entropy, add another word: that helps far more than a rarer word would.

**Should I swap letters for numbers or add capitals?** You can, but it adds less than you would think, because attackers test those substitutions automatically. Adding one more random word is worth about 8 bits; changing an o to a 0 is worth almost nothing. Put your effort into length.

### Password generator
https://hopi.co.uk/password-generator/

Free password generator. Create strong random passwords up to 64 characters with letters, numbers and symbols. Generated in your browser and never transmitted.

**Is my password sent to a server?** No. Passwords are generated by JavaScript running on your own device, using your browser's cryptographic random number generator. Nothing is transmitted, logged or stored, and refreshing the page destroys what was on screen.

**How long should a password be?** 16 characters or more for anything that matters. Length beats cleverness: every extra character multiplies the work an attacker must do, which is why a long password of plain letters can be stronger than a short one full of symbols.

**Do I really need symbols?** Symbols help, but length helps more. A 20-character password of letters and numbers is far stronger than a 10-character one with symbols. Include symbols when the site allows them, but never at the cost of length.

**How am I supposed to remember passwords like this?** You are not. Use a password manager (the ones built into iPhone, Android and modern browsers are fine) and let it remember a unique random password for every site. You then only memorise one strong master password.

**What makes a generated password stronger than one I invent?** Humans are predictable: names, dates, keyboard walks and word-plus-number patterns are all in every attacker's dictionary. A random generator has no patterns to exploit, so the only attack left is brute force, which length makes impractical.

### QR code generator
https://hopi.co.uk/qr-code-generator/

Free QR code generator. Turn any link or text into a scannable QR code in your browser and download it as a PNG, JPG or SVG at any size up to 4096 px.

**Do QR codes made here expire?** No. The code is a static picture that encodes your text directly, with no shortening service in the middle, so it works for as long as whatever it points at still exists. There are no scan limits and nothing to renew.

**Can I use the codes commercially?** Yes. Codes you generate are yours to print on menus, packaging, posters or anything else, free of charge. Note that QR Code is a registered trademark of DENSO WAVE INCORPORATED, which covers use of the name rather than your right to make and use the codes.

**How much text fits in a QR code?** Up to a few thousand characters, but the more you pack in, the denser and harder to scan the code becomes. For links, shorter is better: a tidy URL produces a coarse, forgiving pattern that scans first time from further away.

**Why will my code not scan?** The usual culprits are printing it too small for the scanning distance, weak contrast between the code and its background, or cramming in a very long URL. Export it at a larger pixel size, keep dark modules on a light background, and test with a phone before you print.

**Is my link or text uploaded anywhere?** No. The code is generated entirely in your browser and nothing is sent to a server, so it is safe to make codes for private links and internal documents.

### Random coordinates generator
https://hopi.co.uk/random-coordinates/

Free random coordinates generator. Create latitude and longitude points spread evenly over the globe, with OpenStreetMap links, using cryptographic randomness.

**Why do most points land in the sea?** Because most of the planet is sea. Roughly 71% of the Earth's surface is ocean, so a fair generator will put roughly 7 in every 10 points in water. If your points mostly show blue on the map, that is the generator being honest, not broken.

**Why not just pick a random latitude between -90 and 90?** Because lines of latitude get shorter towards the poles. Picking latitude uniformly would crowd points into the polar regions, where each degree of latitude covers far less area. This tool applies an arcsine correction so every square kilometre of the globe is equally likely, which is what people almost always actually want.

**Can I get land-only coordinates?** Not here, honestly. Deciding whether a point is on land needs a detailed coastline dataset several megabytes in size, and a crude approximation would quietly bias the results. Generate a few extra points instead and keep the ones that suit you.

**What do the map links show?** Each link opens OpenStreetMap centred on the exact point, with a marker, at a zoom level that shows the surrounding region. Nothing about your click is sent from this page; you are simply visiting the map site with the coordinates in the address.

**How random are the points?** Each coordinate is built from your browser's cryptographic random number generator (crypto.getRandomValues), the same source used for encryption keys. The draw happens on your device and cannot be predicted or influenced by anyone, including us.

### Random letter generator
https://hopi.co.uk/random-letter-generator/

Free random letter generator. Pick one letter or a whole batch from A to Z, or limit the draw to vowels or consonants. Fair picks via cryptographic randomness.

**Is every letter equally likely?** Yes. Each draw uses your browser's cryptographic random number generator with rejection sampling, so all 26 letters have an identical 1 in 26 chance. That is quite unlike written English, where E appears far more often than Z.

**Can the same letter come up twice?** Yes. Each draw is independent, like rolling a 26-sided die, so a batch of ten letters can easily contain repeats. If you need every letter to be different, draw them one at a time and skip any you have already had.

**Which letters count as vowels?** A, E, I, O and U. The consonants set holds the other 21 letters. Y sometimes acts as a vowel in English words, but for this tool it is treated as a consonant, which matches how most word games handle it.

**Why are the letters in capitals?** Capitals are easier to read at a glance and avoid confusion between lookalikes such as lower case l and capital I. The draw itself is identical either way, since case does not change which letter was picked.

**What is a random letter useful for?** Party and classroom games such as name, place, animal, thing, picking who goes first by initial, phonics practice with children, creative writing prompts and quiz rounds. Anywhere you need a letter nobody chose on purpose.

### Random number generator
https://hopi.co.uk/random-number-generator/

Free random number generator. Pick random numbers between any minimum and maximum, one or many at once, with or without repeats. Uses cryptographic randomness.

**Are the minimum and maximum included?** Yes. The range is inclusive at both ends, so 1 to 10 can produce both 1 and 10, and every whole number in between with equal probability.

**Is this truly random?** It uses your browser's cryptographic random number generator (crypto.getRandomValues), which draws on operating system entropy. That is far stronger than the basic Math.random most tools use, and more than fair enough for draws, raffles and games. Only physical processes like radioactive decay are truly random in the strictest sense.

**Can the same number come up twice?** With repeats allowed (the default), yes, exactly like rolling a dice. Tick no repeats to draw unique numbers, like pulling raffle tickets from a hat. In that mode the quantity cannot exceed the size of the range.

**Is it fair for a prize draw?** Yes. Every number in the range has an equal chance, the generator avoids the bias that naive methods introduce, and each click is independent. For an auditable draw, agree the range and click once in front of a witness.

**How big can the range be?** Anything up to about 9 quadrillion (JavaScript's safe integer limit), so ranges like 1 to 1,000,000,000 are no problem.

### Random team generator
https://hopi.co.uk/random-team-generator/

Free random team generator. Paste a list of names, pick how many teams you need and get a fair, unbiased random split in one click. Runs in your browser.

**How does it split people fairly?** The full list of names is shuffled with the Fisher-Yates algorithm, driven by your browser's cryptographic random number generator, then dealt into teams in turn like a pack of cards. Every possible arrangement of people is equally likely, so no name and no position in your list gets an advantage.

**What happens when the names do not divide evenly?** The earlier teams get one extra player each. Eleven names in three teams gives 4, 4 and 3, and because the shuffle is random it is pure chance who lands in the bigger teams. If exact evenness matters, choose a team count that divides your group.

**Can I re-run it if the teams look lopsided?** Yes, every click is a completely fresh shuffle. Bear in mind that a fair draw can still produce teams that look uneven in skill, because the tool only knows names. For friendly games many groups agree in advance to accept the first result.

**How many names and teams can I use?** Between 2 and 20 teams, and as many names as you can paste, so a whole school year group is no problem. Each name goes on its own line, blank lines are ignored, and you need at least one name per team.

**Is my list of names uploaded anywhere?** No. The shuffle happens entirely on your device in JavaScript. Names are never transmitted, logged or stored, and leaving the page clears everything, so it is safe to use with classroom or staff lists.

### Random word generator
https://hopi.co.uk/random-word-generator/

Free random word generator. Draw random common English words for party games, writing prompts and brainstorming, one to twenty at a time, free in your browser.

**How are the words chosen?** Each word is drawn from a list of 200 common English nouns using your browser's cryptographic random number generator, the same source used for encryption keys. Every word has an exactly equal chance on every draw, and each click is independent of the last.

**Can the same word appear twice in one batch?** No. Within a single click every word is unique, like pulling raffle tickets from a hat. Click again and any word can of course come back, because each batch is a fresh draw from the full list.

**What kind of words are in the list?** Two hundred everyday concrete nouns: animals, food, places, household objects and things you can point at. They are all family friendly, so the tool is safe for classrooms and party games with children.

**What can I use random words for?** Party games such as Pictionary, charades and twenty questions, writing prompts, vocabulary practice, naming brainstorms and icebreakers. Anywhere you need a word nobody chose on purpose, a random draw keeps things fair and surprising.

**Is anything sent to a server?** No. The draw happens entirely on your device in JavaScript. Nothing you generate is transmitted, logged or stored, and refreshing the page clears the result.

### Reaction time test
https://hopi.co.uk/reaction-time-test/

Free reaction time test. Wait for the box to turn green, click as fast as you can, and see your reaction time in milliseconds, with an average and best.

**How is my reaction time measured?** The box turns green at a random moment, a high resolution browser clock starts, and it stops the instant you click. The gap, in milliseconds, is your reaction time. The clock has sub-millisecond precision, so the number reflects your reflexes and your device rather than any rounding.

**What is a normal reaction time?** For a simple visual signal like this, most people land somewhere around 200 to 300 milliseconds, with 250 a common average. Well under 200 is very fast. Times drift up when you are tired, and down a little with practice, so treat any single go as a rough snapshot.

**Why did it say too soon?** You clicked while the box was still red, before it turned green. That measures anticipation, not reaction, so the attempt is thrown out and you start again. Waiting for the colour to actually change is the whole test.

**Why does the delay before green vary?** The wait is randomised between about 1.5 and 4.5 seconds precisely so you cannot predict it. If the green always appeared after the same pause, you would learn the timing and jump the gun, and the test would measure memory rather than reaction.

**Does my device affect the result?** A little. Screen refresh rate, mouse or touchscreen response and the browser all add a few milliseconds that are outside your control, so scores are best compared on the same device. Everything runs in your browser and nothing is uploaded.

### Scratch card
https://hopi.co.uk/scratch-card/

Free online scratch card. Type your own outcomes, one per line, then scratch off the foil to reveal the one drawn at random. A toy for reveals, not gambling.

**When is the outcome decided?** The moment a new card is made, before you scratch anything. Your browser's cryptographic random number generator picks one line from your list and hides it under the foil. Scratching only reveals what is already there, so where and how you scratch makes no difference.

**Can I change the odds of an outcome?** Yes. Every line gets an equal chance, so repeat a line to weight it. If your list has four lines and one of them appears twice, that outcome has a 2 in 5 chance. Most real prize draws work best with lots of try again lines and one rare winner.

**Why did the card finish revealing itself?** Once you have scratched away about 60% of the foil, the card clears the rest for you. That matches how people use real scratch cards: by that point the answer is obvious, and the auto reveal saves your finger the last few rubs.

**Does it work on phones and tablets?** Yes. The foil responds to any pointer, so you can scratch with a finger, a stylus, a mouse or a trackpad. Everything runs in your browser and your list of outcomes never leaves your device.

**Is this gambling?** No. It is a toy. Nothing is staked, nothing is paid out, and you write every outcome yourself, so there are no hidden odds. Real scratch cards are a form of gambling with a house edge and an age limit of 18 in the UK, which is a different thing entirely.

### Secret Santa generator
https://hopi.co.uk/secret-santa-generator/

Free Secret Santa generator. Add names one per line and draw who buys for whom. Nobody draws themselves, and the draw happens privately in your browser.

**Can two people end up buying for each other?** Yes. The only rule the draw enforces is that nobody gets their own name, so mutual pairs happen naturally, especially in small groups (with two people it is the only possible outcome). If your group prefers to avoid swaps, simply draw again before announcing anything.

**How do I keep the results secret?** The person who runs the draw sees every pair, so either pick an organiser who is happy knowing, ask someone outside the group to click the button, or have the organiser copy the list and message each person only their own line. Once sent, delete the copied list.

**Is the draw fair?** Yes. The names are shuffled with your browser's cryptographic random number generator and reshuffled until nobody has themselves. Every valid arrangement is equally likely, so no one is more likely to draw any particular person than anyone else.

**How many people do I need?** At least two, though it only becomes a proper Secret Santa from about four, since with two or three people it is easy to work out who has you. There is no upper limit that matters for an office or family draw.

**Are the names sent anywhere?** No. The draw runs entirely in your browser, nothing is uploaded, and refreshing the page clears both the names and the results.

### Slot machine name picker
https://hopi.co.uk/slot-machine-picker/

Free slot machine name picker. Add names one per line, spin the reel and watch it blur, slow and stop on a random winner, then remove them and spin again.

**Is the reel fair?** Yes. The winner is chosen by your browser's cryptographic random number generator before the reel even starts moving, and every name gets exactly the same chance. The spin, the blur and the slowdown are pure theatre, so the timing of your click makes no difference.

**How many names can I add?** Up to 100, one per line. However long the list, the draw stays perfectly fair, because the winner is picked by the random number generator rather than by where the reel happens to stop.

**How is this different from the wheel spinner?** Same fair randomness, different show. The wheel lays every name out in a circle and spins them all at once, while the reel scrolls the names past a window and stops on one, like a fruit machine. Use whichever builds the better suspense for your crowd.

**Can the same name win twice?** Yes, if you spin again without removing it, since every spin is an independent draw. Use the remove winner and spin again button between draws to pick several different winners, for example first, second and third prizes.

**Are the names uploaded anywhere?** No. The reel is built and spun entirely in your browser, the names never leave your device, and refreshing the page clears them.

### Spin the bottle
https://hopi.co.uk/spin-the-bottle/

Free spin the bottle game. Add player names around the circle, spin the bottle and see who it points at, or spin with no names for a random angle.

**Is the spin actually random?** Yes. The moment you click spin, your browser's cryptographic random number generator picks the result, and the bottle animation then slows to a stop on it. Timing your click, spinning harder or spinning again quickly makes no difference to the odds.

**Do I have to add names?** No. With an empty list the bottle simply spins and stops at a random angle, shown in degrees, which works fine if your players are sitting in a real circle around the screen. Add names and the tool arranges them around the bottle and announces whoever it lands on.

**How many players can I add?** Up to 20, which is about as many as fit legibly around the circle. Every player gets an equal slice of the circle, so the game stays fair however many you add.

**Can the bottle land between two players?** No. The winner is chosen first and the bottle always comes to rest clearly inside that player's slice of the circle, and the name is announced in the result panel as well. There is nothing to argue about.

**Are the names uploaded anywhere?** No. The circle is drawn and spun entirely in your browser, the names never leave your device, and refreshing the page clears them.

### Typing speed test
https://hopi.co.uk/typing-speed-test/

Free typing speed test. Type a short passage and get your words per minute, accuracy percentage and highlighted mistakes live. No sign up, runs in your browser.

**How is words per minute worked out?** The standard way: every five characters you type counts as one word, and that word count is divided by the minutes elapsed. So 250 characters in one minute is 50 words per minute. Using five characters as a word keeps the score fair whether you type long words or short ones.

**When does the timer start?** On your very first keystroke, not when the page loads. That means you can read the passage and get comfortable first, then start typing when you are ready. The timer stops automatically the moment you finish the passage.

**What does the accuracy figure mean?** It is the share of the passage you typed correctly, character by character. Mistyped characters are highlighted in the passage as you go, so you can see exactly where you slipped. Accuracy and speed pull against each other, and both matter.

**Is a good score more about speed or accuracy?** Both, because errors cost time to fix in real writing. Aim for a speed you can hold with accuracy above about 95 percent. A slightly slower, cleaner run usually beats a fast one full of corrections.

**Is anything I type sent anywhere?** No. The passages are built into the page and your typing is compared against them entirely in your browser. Nothing is uploaded, logged or stored, and refreshing the page starts a clean test.

### Username generator
https://hopi.co.uk/username-generator/

Free username generator. Get random adjective and noun username ideas with an optional two-digit number, six suggestions per click. Click any name to copy it.

**How are the usernames generated?** Each suggestion pairs one of 60 adjectives with one of 60 nouns, both picked by your browser's cryptographic random number generator, then adds a random two-digit number if the box is ticked. That gives 324,000 possible combinations, all generated on your device with nothing sent to a server.

**Will the username be available on every site?** There is no way to guarantee that, because every site keeps its own register of taken names. The suggestions here are random enough that most will be free on most platforms, and if one is taken you can click Generate again or tweak the number.

**Should my username include personal details?** No. Usernames are public, so avoid your real name, birth year, postcode or anything else you would not print on a badge. A random adjective and animal says nothing about you, which is exactly what you want from a public handle.

**Are the suggestions suitable for children?** Yes. Both word lists are made of ordinary, family-friendly words, and because no personal information is involved the results are safe for children's gaming and school accounts. An adult should still check the chosen platform's own rules.

**Is a username the same as a password?** No, and they do different jobs. A username is public and just needs to be unique and non-identifying. A password is secret and needs to be long and random, so generate it separately with a password or passphrase generator and never reuse the username as the password.

### Wheel spinner
https://hopi.co.uk/wheel-spinner/

Free wheel spinner. Add names one per line, spin the wheel and let it pick a random winner, then remove them and spin again. Fair, instant and free.

**Is the wheel fair?** Yes. The winner is chosen by your browser's cryptographic random number generator, the same machinery used to create encryption keys, and every name gets exactly the same chance. The animation then lands on the chosen segment, so timing your click makes no difference.

**How many names can I add?** Up to 100. The labels get small once you pass about 20 names, but the draw stays perfectly fair however many segments there are, because the winner is picked by the random number generator rather than read off the drawing.

**Can the same name win twice?** Yes, if you spin again without removing it, exactly like spinning a real wheel twice. Use the remove winner button after each spin to draw several different winners, for example for first, second and third prizes.

**What happens if I add the same name twice?** It gets two segments and therefore twice the chance of winning. Usually that is a mistake worth fixing, but you can also use it deliberately to weight the wheel, for example giving one entry per raffle ticket bought.

**Are the names uploaded anywhere?** No. The wheel is drawn and spun entirely in your browser, the names never leave your device, and refreshing the page clears them.

### Yes or no
https://hopi.co.uk/yes-no-wheel/

Free yes or no generator. Ask a question, press once and get an instant yes or no (or maybe), with a running tally. Fair answers via cryptographic randomness.

**Is the answer really 50/50?** Yes. Each press uses your browser's cryptographic random number generator (crypto.getRandomValues), so yes and no are exactly equally likely. With the maybe option ticked, all three answers have an identical 1 in 3 chance.

**What does the maybe option do?** It adds a third possible answer alongside yes and no, each with an equal 1 in 3 chance. Use it when deferring is a genuine option, for example asking whether to buy something now, where maybe can stand for ask again next week.

**Why do I keep getting the same answer?** Streaks are a normal part of randomness. Three identical answers in a row has a 1 in 8 chance in yes/no mode, so it happens often. Every press is independent, and past answers never influence the next one.

**Should I actually follow the answer?** For trivial choices, absolutely, that is the point. For bigger ones, use it as a gut check: notice your reaction the moment the answer appears. Relief or disappointment tells you what you really wanted, and you are free to overrule the button.

**How is this different from flipping a coin?** The odds are identical in yes/no mode, a fair 50/50. The differences are convenience (your question is answered in words, not heads or tails) and the optional maybe answer, which a coin cannot give you. Our coin flip tool keeps a heads and tails tally instead.

## Converters & units

### Angle converter
https://hopi.co.uk/angle-converter/

Free angle converter. Turn degrees, radians, gradians and turns into each other instantly, with radians shown as a clean multiple of pi where possible.

**How many radians are in 360 degrees?** A full circle is 2 pi radians, which is about 6.2832. So 180 degrees is pi radians (about 3.1416) and 90 degrees is pi over 2 (about 1.5708). Radians measure angle as arc length divided by radius, which is why the circle's circumference of 2 pi radii gives 2 pi radians.

**How do I convert degrees to radians?** Multiply the degrees by pi and divide by 180. For example 45 degrees times pi over 180 is pi over 4, about 0.7854 radians. To go back, multiply radians by 180 and divide by pi.

**What is a gradian?** A gradian, also called a grad or gon, splits a right angle into 100 parts, so a full circle is 400 gradians. It was designed to make a quarter turn a round number and is still used in some surveying and civil engineering. 100 gradians equals 90 degrees.

**What is a turn?** A turn is one full rotation, so 1 turn is 360 degrees, 2 pi radians or 400 gradians. Fractions of a turn are an intuitive way to describe rotation: a half turn is 180 degrees and a quarter turn is 90 degrees. It is common in engineering and computer graphics.

**Which angle unit should I use?** Degrees suit everyday and navigation work. Radians are the natural unit for mathematics and physics because they make calculus of trig functions clean. Gradians appear in surveying, and turns are handy for describing rotations. This tool shows all four at once so you can pick whichever the task needs.

### Area converter
https://hopi.co.uk/area-converter/

Free area converter. Turn square metres, square feet, square yards, acres, hectares and square miles into each other instantly, with exact factors.

**How many square feet are in a square metre?** About 10.764 sq ft. A square foot is exactly 0.09290304 square metres, so to go from square feet to square metres multiply by 0.0929, and to go the other way multiply by 10.764. A 1,000 sq ft house is about 92.9 square metres.

**How big is an acre?** Exactly 4,840 square yards, which is 4,046.86 square metres or 43,560 square feet. That is about 15 and a half doubles tennis courts (a doubles court is 78 by 36 feet, so 2,808 sq ft), or a little over half a full-size football pitch. In hectares it is about 0.4047 ha.

**What is the difference between a hectare and an acre?** A hectare is metric: the area of a square 100 m by 100 m, so exactly 10,000 square metres. An acre is the older imperial unit of 4,840 square yards. One hectare is about 2.47 acres, and one acre is about 0.4 hectares. UK land is officially registered in hectares but often still marketed in acres.

**How do I convert a house size in sq ft to square metres?** Multiply by 0.0929. A 750 sq ft flat is about 69.7 square metres, and a 1,500 sq ft house is about 139.4 square metres. UK estate agents mix both units freely, so it is worth converting before comparing two listings.

**Why is the square feet factor not the same as the feet factor?** Because area scales with the square of the length factor. A foot is 0.3048 metres, but a square foot is 0.3048 times 0.3048, which is 0.09290304 square metres. Forgetting to square the factor is the classic area conversion mistake, and it makes answers wrong by more than 3 times.

### Aspect ratio calculator
https://hopi.co.uk/aspect-ratio-calculator/

Free aspect ratio calculator. Simplify a resolution like 1920x1080 to 16:9, or work out the missing width or height from a ratio, with common presets.

**What is an aspect ratio?** An aspect ratio is the relationship between a shape's width and its height, written width first as W:H. A 16:9 screen is 16 units wide for every 9 units tall. It describes the shape only, not the actual size, so 1280x720 and 1920x1080 are both 16:9.

**How do I simplify a resolution to a ratio?** Divide both numbers by their greatest common divisor. For 1920x1080 the greatest common divisor is 120, and 1920 divided by 120 is 16 while 1080 divided by 120 is 9, giving 16:9. The simplify mode here does this for you as you type.

**What height do I need for a 16:9 video at 1920 wide?** Multiply the width by 9 and divide by 16: 1920 times 9 is 17,280, divided by 16 is 1,080. So a 16:9 frame that is 1920 pixels wide is 1080 pixels tall. The solve mode does this for any ratio and either side.

**What are the common aspect ratios?** 16:9 is standard for TVs, phones in landscape and most video. 4:3 is old TVs and many tablets. 21:9 (really 64:27) is ultrawide monitors and cinema. 1:1 is square social posts, 9:16 is vertical video and stories, and 3:2 is common in photography.

**Does changing the aspect ratio affect image quality?** Resizing within the same ratio keeps the shape and just scales the pixels. Changing the ratio means either stretching the image (which distorts it) or cropping part of it away. To fit a different ratio without distortion, crop rather than stretch, then resize.

### Cm to feet converter
https://hopi.co.uk/cm-to-feet/

Free cm to feet converter. Turn centimetres into feet and inches (or feet and inches back into cm) instantly, with a height chart and the exact formula.

**How many centimetres are in a foot?** Exactly 30.48 cm. A foot is 12 inches and an inch is defined as exactly 2.54 cm, so the conversion is precise rather than approximate.

**What is 5 foot 10 in cm?** 5 ft 10 in is 70 inches, and 70 × 2.54 = 177.8 cm. Going the other way, 180 cm is 5 ft 10.9 in, which usually gets called 5 foot 11.

**How do I convert cm to feet and inches by hand?** Divide the centimetres by 2.54 to get total inches, then divide by 12: the whole number is the feet and the remainder is the inches. For 175 cm: 175 ÷ 2.54 = 68.9 in = 5 ft 8.9 in.

**Why does the UK use both systems for height?** Britain metricated officially but conversational habits stayed imperial: people describe themselves in feet and inches while the NHS, passports and gyms record centimetres. Most Britons under 50 know their height in both, or need this page to bridge them.

**How is the inches figure rounded?** To one decimal place. If rounding pushes the inches to 12.0 the feet tick up instead, so you will never see an answer like 5 ft 12 in.

### Cups to grams converter
https://hopi.co.uk/cups-to-grams/

Free cups to grams converter for baking. Turn US cup measures into grams for flour, sugar, butter, cocoa, oats and more, with a full ingredient table.

**How many grams is a cup of flour?** A US cup of plain flour weighs about 120 g. This is approximate because flour compresses: a scooped and packed cup can weigh 20 g more than a spooned and levelled one. Weighing is always more accurate.

**Why do cups convert to different grams for different ingredients?** A cup measures volume, not weight, and ingredients have different densities. A cup of caster sugar weighs about 200 g while the same cup of oats weighs only about 90 g. That is why each ingredient needs its own conversion.

**Is a UK cup the same as a US cup?** Not quite. A US cup is about 240 ml, while older UK and Australian recipes use a 250 ml cup. The difference is small but it adds up in large quantities. This tool uses the US cup, since cup-based recipes are almost always American.

**How many grams is a stick of butter?** One US stick of butter is half a cup, which is about 113 g. Two sticks make a full cup at about 225 g. UK butter blocks are 250 g, so a stick is just under half a block.

**Why do UK recipes use grams instead of cups?** Because weight does not change with how you pack, scoop or sieve an ingredient. British and European recipes standardised on scales for repeatable results, and most serious American baking sites now list gram weights too. Use grams whenever a recipe offers both.

### Data size converter
https://hopi.co.uk/data-size-converter/

Free data size converter for KB, MB, GB and TB, with a switch between decimal (1000) and binary (1024) units. Explains KB vs KiB and drive sizes.

**How many MB are in a GB?** In decimal units, 1,000 MB make a GB, and that is how storage is sold and how this tool works by default. In binary units, 1,024 MiB make a GiB. Tick the binary box if you want the 1024-based figures.

**What is the difference between KB and KiB?** KB (kilobyte) officially means 1,000 bytes, using the metric prefix. KiB (kibibyte) means 1,024 bytes, the power-of-two unit computers naturally use. Historically KB was used loosely for both, which is the root of most data size confusion.

**Why does my 1 TB drive show as 931 GB?** The manufacturer counts in decimal: 1 TB = 1,000,000,000,000 bytes. Windows divides that same number of bytes by 1,073,741,824 (binary) and labels the result GB, giving 931. No space is missing, the two sides are just using different definitions of the same unit names.

**Should I use decimal or binary units?** Decimal matches how storage and broadband are marketed, so it is the default here. Binary matches what Windows reports for drives and what memory (RAM) uses. If you are comparing a file size on screen with an advertised capacity, convert both through bytes, which is exactly what this tool does.

**How big is a typical file?** As a rough guide: a plain email is a few KB, a smartphone photo is 2 to 5 MB, an hour of streamed HD video is around 3 GB, and modern games can exceed 100 GB. A 4.7 GB DVD holds about 4.38 GiB in binary terms.

### Download time calculator
https://hopi.co.uk/download-time-calculator/

Free download time calculator. Enter a file size and your broadband speed in Mbps or MB/s to estimate the time, with the 8-bits-per-byte gotcha explained.

**Why does the download take longer than my broadband speed suggests?** Broadband is sold in megabits per second (Mbps), but files are measured in bytes, and there are 8 bits in a byte. So a 100 Mbps line moves at most 12.5 MB per second. On top of that, real speeds fall short of the advertised figure because of overheads, Wi-Fi, distance and the server at the other end.

**What is the difference between Mbps and MB/s?** Mbps is megabits per second, the unit for line speed. MB/s is megabytes per second, the unit for how fast a file actually lands. There are 8 bits in a byte, so you divide Mbps by 8 to get MB/s. 80 Mbps is 10 MB/s. Watch the case: small b is bits, big B is bytes.

**How long does a 1 GB file take on 100 Mbps?** 1 GB is 8,000 megabits (1,000 MB times 8). Divide by 100 Mbps and you get 80 seconds, so 1 minute 20 seconds in perfect conditions. Real time is usually a bit longer because you rarely get the full advertised speed.

**Why is the real download slower than this estimate?** This tool gives the theoretical best case: file size in bits divided by line speed in bits per second. In practice you lose time to protocol overhead, Wi-Fi interference, network congestion, and slow servers. Treat the answer as a floor, and expect the real time to be somewhat higher.

**Are file sizes here decimal or binary?** Decimal, matching how storage and broadband are marketed: 1 GB is 1,000 MB and 1,000,000,000 bytes. Windows sometimes reports the same file using binary units (1 GiB = 1,073,741,824 bytes), which makes numbers differ by up to about 7 percent. Our data size converter covers that difference in full.

### Kg to stone converter
https://hopi.co.uk/kg-to-stone/

Free kg to stone converter. Turn kilograms into stones and pounds (or stones back into kg) instantly. Includes the formula and a handy reference table.

**How many kilograms are in a stone?** One stone is exactly 6.35029 kg. Going the other way, one kilogram is 0.157473 stone, or about 2.20462 pounds. There are 14 pounds in a stone.

**What is 75 kg in stones and pounds?** 75 kg is 11 stone 11.3 lb. Multiply 75 by 2.20462 to get 165.3 pounds, divide by 14 to get 11 stone with 11.3 pounds left over.

**Why does the UK weigh people in stones?** The stone is an old imperial unit that survived metrication in everyday speech. Medicine and official records in the UK use kilograms, but most Britons still think of body weight in stones and pounds, which is why UK scales offer both.

**How do I convert stones and pounds back to kg?** Multiply the stones by 14, add the pounds, then multiply the total pounds by 0.453592. For example 12 st 8 lb is 176 lb, and 176 × 0.453592 = 79.8 kg.

**How accurate are the conversions?** The tool uses the exact definitions (1 lb = 0.45359237 kg) and rounds only for display: kilograms to one decimal place and pounds to one decimal place.

### Length converter
https://hopi.co.uk/length-converter/

Free length converter. Turn mm, cm, metres, km, inches, feet, yards and miles into each other instantly, using exact factors, with worked examples.

**How many centimetres are in an inch?** Exactly 2.54 cm. The inch has been defined as exactly 2.54 cm since 1959, so every metric-imperial length conversion on this page is exact rather than approximate. A foot is 30.48 cm and a yard is 91.44 cm.

**How do I convert metres to feet?** Divide the metres by 0.3048, or multiply by about 3.281. For example 100 m is 328.08 ft. Going the other way, multiply feet by 0.3048 to get metres.

**How many kilometres are in a mile?** One mile is exactly 1.609344 km. So 5 miles is 8.05 km, and 5 km is about 3.11 miles. To convert km to miles, divide by 1.609344 or multiply by roughly 0.6214.

**What is the difference between a yard and a metre?** They are close but not equal. A yard is exactly 0.9144 m, so a metre is about 1.094 yards, roughly 9.4 cm longer than a yard. Over 100 metres the difference adds up to more than 9 yards' worth of centimetres, which is why athletics switched to metric distances.

**How accurate are the results?** The tool converts through metres using the exact legal definitions (1 in = 2.54 cm, 1 mi = 1.609344 km) and only rounds for display, to six significant figures. That is more precision than any tape measure can use.

### Litres to pints converter
https://hopi.co.uk/litres-to-pints/

Free litres to pints converter. Turn litres into UK pints (or pints back into litres) instantly, with milk and beer references and the exact formula.

**How many pints are in a litre?** One litre is 1.76 UK pints. The UK pint is defined as 568.261 millilitres, so divide the litres by 0.568261 to get pints. Two litres is 3.52 pints and five litres is 8.80 pints.

**How many litres are in a UK pint?** One UK pint is 0.568261 litres, or 568.261 millilitres. To convert pints to litres, multiply the pints by 0.568261. Four pints is 2.27 litres and six pints is 3.41 litres.

**Is a US pint the same as a UK pint?** No. A US liquid pint is about 473 millilitres while a UK pint is 568.261 millilitres, so a US pint is only about 83 percent of a UK one. This tool shows both, but the main conversion uses the UK pint.

**How many litres is a 4 pint bottle of milk?** A 4 pint bottle holds 2.27 litres, because 4 multiplied by 0.568261 is 2.273. That is why the label on a large UK milk bottle reads 2.272 litres.

**How accurate are the conversions?** The tool uses the exact UK definition of the pint, 568.261 millilitres, and the US liquid pint of 473.176 millilitres. Results are rounded to two decimal places for display only.

### MPG converter
https://hopi.co.uk/mpg-converter/

Free MPG converter. Switch between UK miles per gallon and litres per 100 km instantly, with US mpg, km per litre and a fuel cost example included.

**How do I convert mpg to litres per 100 km?** Divide 282.481 by the mpg figure. Handily the same formula works in reverse: divide 282.481 by the litres per 100 km to get mpg back. So 40 mpg is 7.06 L/100km, and 7.06 L/100km is 40 mpg.

**Is UK mpg the same as US mpg?** No. The imperial gallon is 4.54609 litres but the US gallon is only about 3.785 litres, so the same car scores about 20 percent higher in UK mpg. Multiply a US figure by 1.201 to get the UK equivalent, or divide a UK figure by 1.201 for the US one.

**What is a good mpg for a car?** As a rough guide in UK mpg, over 50 is very economical for a petrol car, 40 to 50 is typical, and under 30 is thirsty. Hybrids often exceed 60 mpg in mixed driving. Real-world figures are usually below the official test numbers.

**Why do car adverts quote litres per 100 km?** Official European fuel economy tests report consumption as litres per 100 km, and lower is better, whereas with mpg higher is better. UK brochures often show both. This tool lets you type either figure and read off the other instantly.

**How much does fuel economy affect cost?** Directly. At 40 mpg, 100 miles uses 2.5 imperial gallons, about 11.4 litres, which costs around £16.50 at £1.45 a litre. The same trip at 50 mpg uses a fifth less fuel, so small mpg differences add up over a year of driving.

### Miles to km converter
https://hopi.co.uk/miles-to-km/

Free miles to km converter that works both ways as you type. 1 mile is exactly 1.609344 km. Includes running distances from the 5K to the marathon.

**How many kilometres are in a mile?** Exactly 1.609344 km. The mile is defined as 1,760 yards and the yard as exactly 0.9144 m, which fixes the mile at 1,609.344 m. For quick mental maths, a mile is about 1.6 km and a kilometre is about 0.62 miles.

**How many miles is a 5K or 10K?** A 5K is 3.11 miles and a 10K is 6.21 miles. Divide the kilometres by 1.609344 to get miles. Parkrun's 5 km course is why many British runners think in kilometres even though road signs use miles.

**How long is a marathon in miles and km?** A marathon is 42.195 km, which is 26.22 miles, usually quoted as 26.2. A half marathon is 21.0975 km, or 13.11 miles, usually quoted as 13.1.

**How do I convert km to miles in my head?** Multiply by 0.6, or slightly better, multiply by 5 and divide by 8. So 80 km is about 50 miles. Going the other way, multiply miles by 8 and divide by 5: 50 miles is about 80 km. The exact factor is 1.609344.

**Is 70 mph the same as 113 km/h?** Very nearly. 70 × 1.609344 = 112.65 km/h, so the UK motorway limit is just under 113 km/h. Speed converts with the same factor as distance because the time part (per hour) does not change.

### Military time converter
https://hopi.co.uk/military-time-converter/

Free military time converter. Turn 24-hour clock times like 1430 into 12-hour am/pm times and back instantly, with a full reference table.

**What is 1430 in normal time?** 2:30 pm. For any 24-hour time from 13:00 to 23:59, subtract 12 from the hours and add pm. So 1430 becomes 2:30, and because 14 is past midday it is 2:30 in the afternoon.

**Is midnight 12 am or 12 pm?** Midnight is 12 am and noon is 12 pm. A memory aid: am runs from midnight to just before noon, so the very first moment of the morning block, midnight, takes the am label. The 24-hour clock avoids the confusion entirely by writing midnight as 00:00 and noon as 12:00.

**Is midnight 0000 or 2400 in military time?** Both appear, and they name the same instant. 0000 treats midnight as the start of the new day, which is the normal convention, while 2400 is occasionally used to mark midnight as the end of the previous day, for example when a document says a deadline of 2400 on Friday. Timetables and digital systems almost always use 0000.

**How do you say military times out loud?** Read the hours and minutes as numbers: 0600 is spoken as zero six hundred (or oh six hundred), 1430 as fourteen thirty, and 2115 as twenty-one fifteen. The word hours is often added at the end, as in fourteen thirty hours. Leading zeros are always spoken.

**Who uses the 24-hour clock?** Most of the world, for anything where am and pm could be misread: the armed forces, hospitals, airlines, railways and emergency services all use it, and most of continental Europe uses it in everyday writing. In the UK it is standard on timetables and digital devices even though people still say times aloud in 12-hour form.

### Number to words converter
https://hopi.co.uk/number-to-words/

Free number to words converter. Turn figures into British English words instantly, with a pounds and pence cheque mode. Handles numbers up to 999 billion.

**How do you write 105 in words in British English?** One hundred and five. British English puts an "and" between the hundreds and whatever follows, so 342 is three hundred and forty-two. American style usually drops the "and".

**When do numbers need a hyphen?** Compound numbers from twenty-one to ninety-nine take a hyphen: twenty-one, forty-seven, ninety-nine. Round tens do not, so forty and ninety stand alone. The hyphen also survives inside bigger numbers, as in three hundred and sixty-five.

**What is the largest number the tool can convert?** It handles whole numbers up to 999,999,999,999, which is nine hundred and ninety-nine billion and change, plus decimals to two places. That comfortably covers cheques, invoices, legal documents and homework.

**How do I write an amount in words on a cheque?** Tick currency mode and copy the result, for example One hundred and five pounds and fifty pence only. Write it on the long line, make sure it matches the figures in the box, and rule a line through any leftover space so nothing can be added.

**Is a billion a thousand million or a million million?** In modern British usage a billion is a thousand million (1,000,000,000), the same as in America. The older British long scale billion of a million million fell out of official use in 1974, and this tool uses the modern meaning.

### Oven temperature converter
https://hopi.co.uk/oven-temperature-converter/

Free oven temperature converter. Enter Celsius, fan oven, Fahrenheit or a gas mark and see all four equivalents instantly, with the full conversion chart.

**What is 180 degrees Celsius in a fan oven?** 160 degrees. The standard rule is to knock 20 degrees Celsius off the conventional temperature for a fan oven, because the moving air transfers heat more efficiently. 180C conventional is also gas mark 4 and roughly 350F.

**What temperature is gas mark 6?** Gas mark 6 is 200C in a conventional oven, 180C in a fan oven and 400F. It is the classic moderately hot setting used for roasting vegetables, pizzas and pastry.

**How do I convert a fan oven temperature to conventional?** Add 20 degrees Celsius. If a recipe says 160C fan, that is 180C in a conventional oven. Going the other way, subtract 20. The rule is a convention rather than physics, but it works well in practice.

**Why do Celsius and Fahrenheit not line up exactly on oven charts?** Gas marks were defined in Fahrenheit, 25 degrees apart from 275F at gas mark 1, and the Celsius values on charts are rounded conventions. Strictly 180C is 356F, but recipe books call it 350F. Ovens are not precise enough for the difference to matter.

**How accurate does an oven temperature need to be?** Most domestic ovens swing 10 to 20 degrees around their set point as the thermostat cycles, so these conversions are well within normal oven tolerance. If baking results seem consistently off, an inexpensive oven thermometer will tell you what your oven really does.

### Power converter
https://hopi.co.uk/power-converter/

Free power converter. Turn watts, kilowatts, horsepower and PS (metric horsepower) into each other instantly, with car engine examples and exact factors.

**What is the difference between hp and PS?** They are two different horsepower definitions. Mechanical horsepower (hp) is 550 foot-pounds per second, which works out at 745.7 watts. PS, metric horsepower, is 75 kilogram-force metres per second, or 735.5 watts. PS is about 1.4 percent smaller, so the same engine always shows a slightly bigger number in PS than in hp.

**What is 100 kW in horsepower?** 100 kW is 134.1 hp, or 136.0 PS. To convert kilowatts to horsepower, multiply by 1.341 for mechanical hp or by 1.360 for PS. Going the other way, 100 hp is 74.6 kW and 100 PS is 73.5 kW.

**Why do car adverts use PS instead of hp?** PS is the traditional continental European unit, standardised in Germany as the DIN horsepower, and most European manufacturers still quote it. UK adverts mix PS and bhp freely, which muddies comparisons because the PS figure is always slightly higher for the same car. The official EU unit is actually the kilowatt, which is why spec sheets list kW alongside.

**Is bhp the same as hp?** For everyday purposes, yes. The b stands for brake, meaning the power was measured at the engine's output shaft with a brake dynamometer rather than calculated on paper. It describes how the figure was measured, not a different sized unit, so bhp converts exactly like mechanical hp in this tool.

**Are these conversions exact?** Yes, apart from display rounding. Mechanical horsepower is defined exactly through the international pound and foot, giving 745.699872 watts, and PS is defined as exactly 735.49875 watts. The tool uses the full factors internally and rounds only for display.

### Pressure converter
https://hopi.co.uk/pressure-converter/

Free pressure converter. Turn bar, psi, kPa and atmospheres into each other instantly, with tyre pressure examples and the exact conversion factors.

**What is 32 psi in bar?** 32 psi is 2.21 bar, or 220.6 kPa. To convert any tyre pressure, multiply psi by 0.0689 to get bar, or multiply bar by 14.5 to get psi. Most UK tyre pressures sit between 30 and 36 psi, which is roughly 2.1 to 2.5 bar.

**What is the difference between bar and atm?** They are close but not identical. A bar is a round metric unit of exactly 100 kPa, while an atmosphere is the average air pressure at sea level, defined as 101.325 kPa. So 1 atm is 1.01325 bar, about 1.3 percent higher than 1 bar.

**Why do UK tyre pressures use psi?** Habit, mostly. Psi (pounds per square inch) is an imperial unit that stuck around on British forecourts and pressure gauges, while car handbooks now usually print both psi and bar. European equipment tends to read in bar, which is why many garage inflators let you switch between the two.

**How many kPa are in a bar?** Exactly 100. The bar was deliberately defined as 100,000 pascals, so kPa to bar is just a matter of moving the decimal point two places. That makes kPa handy as a bridge unit: convert anything to kPa first and bar follows instantly.

**Are these conversions exact?** Yes, apart from display rounding. Bar, kPa and atm are all defined exactly in pascals, and psi comes from the exactly defined pound and inch, giving 1 psi = 6.894757 kPa to the precision shown. The tool uses the full factors internally and rounds only for display.

### Ring size converter
https://hopi.co.uk/ring-size-converter/

Free ring size converter. Turn UK letter ring sizes into US numbers and inside circumference in mm, in any direction, with charts and measuring tips.

**What is a UK N in US ring sizes?** UK N sits at about US 6¾, with an inside circumference of roughly 53.8 mm. It falls exactly between the common US half sizes, and UK N½ lines up with US 7. If the ring you want only comes in US half sizes, most people in an N would take the 7 for comfort rather than squeeze into a 6½.

**How do I measure my ring size at home?** Wrap a thin strip of paper snugly around the base of the finger, mark where it overlaps, and measure the length in millimetres to get the circumference. Do it at the end of the day when fingers are warmest, repeat two or three times, and check the ring can pass over the knuckle. A jeweller will size you properly for free, which is worth it before an expensive purchase.

**Why is the conversion only approximate?** The systems step by different amounts. A UK half letter is about 0.6 mm of circumference while a US quarter size is about 0.64 mm, so the scales slowly drift apart and published charts disagree by up to a quarter of a size, especially at the largest and smallest ends. Band width matters too, since a wide band wears tighter than a slim one.

**What should I do if I am between two sizes?** Go up rather than down. The ring has to clear your knuckle, fingers swell in heat and through the day, and a slightly loose ring is far more wearable than a tight one. For chunky bands of 6 mm or more, jewellers usually suggest an extra half size. Most plain metal rings can also be resized a size or so either way later.

**Do men and women use different ring size scales?** No, the scales are the same for everyone; only the typical range differs. Most women's rings in the UK fall between about J and P (roughly US 5 to 8) and most men's between about P and W (roughly US 8 to 11½). Hands vary hugely though, so measure rather than guess.

### Shoe size converter
https://hopi.co.uk/shoe-size-converter/

Free shoe size converter. Turn UK shoe sizes into their EU and US equivalents for men and women, half sizes included, with full charts and fit advice.

**What is a UK 9 in EU and US sizes?** For men, a UK 9 is about an EU 43 and a US 10. For women, a UK 9 is about an EU 42 and a US 11. Men's US sizes run one ahead of UK, women's US sizes run two ahead.

**Are men's and women's shoe sizes converted differently?** Yes. UK and US men's sizes differ by one (UK 8 is US 9) but UK and US women's sizes differ by two (UK 5 is US 7). EU sizes are unisex, though the UK to EU offset used on charts is usually 34 for men and 33 for women.

**Why is the conversion only approximate?** Because the systems do not line up exactly. EU sizes step in Paris points of two thirds of a centimetre while UK and US sizes step in thirds of an inch, and every brand shapes its lasts differently. Two brands can label the same shoe EU 42 and EU 42.5, so always check the brand's own chart when buying.

**Do half sizes convert cleanly?** Roughly. A half size in UK terms is about half a size in US terms and half a European size, and the tool follows that through. Half sizes are where charts disagree most though, so if you are between sizes in one system expect to be between sizes in the others too.

**How do I find my size accurately?** Measure your foot length in centimetres at the end of the day, standing, from heel to longest toe, and compare it against the sizing chart of the brand you are buying. Foot length is the one measurement every brand chart shares, so it beats converting between size systems.

### Speed converter
https://hopi.co.uk/speed-converter/

Free speed converter. Turn mph, km/h, metres per second, knots and Mach into each other instantly, using exact factors, with worked driving examples.

**How do I convert mph to km/h?** Multiply by 1.609344, the exact number of kilometres in a mile. So the UK motorway limit of 70 mph is 112.65 km/h. Going the other way, divide by 1.609344: a 100 km/h limit abroad is 62.14 mph.

**What is a knot?** One nautical mile per hour. The nautical mile is exactly 1,852 metres, so a knot is 1.852 km/h, or about 1.15 mph. Knots are the standard for ships, aircraft and wind speeds in marine forecasts, because the nautical mile matches one minute of latitude.

**How fast is Mach 1?** About 761 mph or 1,225 km/h at sea level in air at 15 degrees Celsius, which is the figure this tool uses. The speed of sound falls as air gets colder, so at airliner cruising altitude Mach 1 is closer to 660 mph. Treat any Mach conversion as approximate unless you know the air conditions.

**What is a fast running speed in mph?** A 30 minute 5K works out at 10 km/h, which is 6.2 mph. An elite marathon runner holds around 21 km/h (13 mph) for the whole race, and Usain Bolt's 9.58 second 100 m averaged 37.6 km/h, about 23.4 mph.

**Why are UK speed limits in mph when most countries use km/h?** Britain planned to metricate road signs in the 1970s but never did, so speed limits, distance signs and car odometers stayed in miles. Most of the rest of the world signs in km/h, which is why hire cars abroad and imported dash cams so often need this conversion.

### Temperature converter
https://hopi.co.uk/celsius-to-fahrenheit/

Free Celsius to Fahrenheit converter that works both ways as you type. Includes the formula, worked examples and reference temperatures for ovens and weather.

**How do I convert Celsius to Fahrenheit?** Multiply by 9, divide by 5, then add 32. So 20°C is 20 × 9 ÷ 5 = 36, plus 32 gives 68°F. Going the other way, subtract 32 first, then multiply by 5 and divide by 9.

**What is normal body temperature in both scales?** Around 37°C, which is 98.6°F. Anything from about 36.1°C to 37.2°C is considered normal, and the NHS treats 38°C (100.4°F) or above as a fever.

**At what temperature are Celsius and Fahrenheit equal?** At minus 40. Set C = F in the conversion formula and the only solution is -40, so -40°C and -40°F are exactly the same temperature.

**What is 180°C in Fahrenheit for baking?** 356°F, which American recipes usually round to 350°F. In practice ovens are nowhere near precise enough for the 6 degree difference to matter, so treat 180°C and 350°F as the same moderate oven.

**Why does Fahrenheit use 32 for freezing?** Fahrenheit set his zero at the coldest brine mixture he could reproduce, which left pure water freezing at 32 degrees on his scale. Celsius later defined a scale with water freezing at 0 and boiling at 100, which is the one most of the world adopted.

### Volume converter
https://hopi.co.uk/volume-converter/

Free volume converter. Turn millilitres, litres, UK pints, UK and US gallons, fluid ounces and cubic metres into each other instantly, with exact factors.

**How many millilitres are in a UK pint?** 568.26 ml, or exactly 568.26125 ml. The UK pint is one eighth of the imperial gallon, which is defined as exactly 4.54609 litres. A US pint is smaller at about 473.18 ml, which is why American pint glasses hold noticeably less beer.

**What is the difference between a UK gallon and a US gallon?** The UK (imperial) gallon is exactly 4.54609 litres, while the US gallon is exactly 3.785411784 litres, so the UK gallon is about 20 percent bigger. This matters for fuel economy: a car doing 40 miles per UK gallon would only score about 33.3 miles per US gallon on the same journey.

**Are UK and US fluid ounces the same?** No, and the difference runs the opposite way to pints. A UK fluid ounce is about 28.41 ml while a US fluid ounce is about 29.57 ml, so the US ounce is slightly bigger even though the US pint is smaller. That works because a UK pint holds 20 UK fluid ounces but a US pint holds only 16 US fluid ounces.

**How many litres are in a gallon of petrol?** UK forecourts have sold fuel in litres since the 1980s, but mpg survived, so the useful factor is 4.54609 litres per UK gallon. A 50 litre tank is about 11 UK gallons. If you are reading an American source, its gallon is 3.785 litres, so a 50 litre tank is about 13.2 US gallons.

**How many litres are in a cubic metre?** Exactly 1,000 litres, which is why water meters bill in cubic metres. One cubic metre is about 12 and a half baths at 80 litres each, or roughly 1,760 UK pints. Going the other way, a litre is exactly 1,000 cubic centimetres.

### Weight converter
https://hopi.co.uk/weight-converter/

Free weight converter. Turn grams, kilograms, ounces, pounds and stones into each other instantly, using exact factors, with worked examples included.

**How many grams are in an ounce?** Exactly 28.349523125 g. That comes straight from the definition of the pound (453.59237 g) divided by 16. For kitchen purposes, 28.35 g per ounce is accurate to a hundredth of a gram.

**How do I convert kilograms to pounds?** Multiply by about 2.20462. So 5 kg is 11.02 lb and 70 kg is 154.3 lb. Going the other way, multiply pounds by 0.45359237 to get kilograms.

**How many pounds are in a stone?** 14 pounds, which makes a stone exactly 6.35029318 kg. Body weight in the UK is usually quoted in stones and pounds, so 11 stone 11 lb is 165 lb, or about 74.8 kg.

**Is a UK ounce the same as a US ounce?** For weight, yes. Both countries use the avoirdupois ounce of 28.349523125 g. The confusion comes from fluid ounces, which measure volume and do differ: a UK fluid ounce is 28.41 mL and a US one is 29.57 mL.

**How accurate are the results?** The tool converts through grams using the exact definition 1 lb = 0.45359237 kg and only rounds for display, to six significant figures. Kitchen and bathroom scales round far more aggressively than that.

## Health & fitness

### Alcohol unit calculator
https://hopi.co.uk/alcohol-unit-calculator/

Free alcohol unit calculator. Enter ABV and volume or tap a drink preset to get UK units per drink, plus your weekly total against the NHS 14 unit guideline.

**What is a unit of alcohol?** One unit is 10 millilitres (8 grams) of pure alcohol, the amount an average adult processes in roughly an hour. It is a UK measure designed to make different drinks comparable, because a pint of beer, a glass of wine and a shot of spirits all contain different amounts of alcohol.

**How do I work out the units in a drink?** Multiply the ABV percentage by the volume in millilitres, then divide by 1,000. A pint of 4% beer is 4 times 568 divided by 1,000, which is 2.27 units. The formula works because ABV tells you what percentage of the liquid is pure alcohol, and one unit is 10 ml of it.

**How many units are in a bottle of wine?** A 750 ml bottle at 13% ABV contains 9.75 units, so close to 10. At 12% it is exactly 9 units. A medium 175 ml glass of 13% wine is about 2.3 units and a large 250 ml glass is about 3.3 units.

**What is the NHS guideline for alcohol?** The UK Chief Medical Officers advise that both men and women are safest not drinking more than 14 units a week on a regular basis, spread over three or more days, with several drink-free days. The guideline describes a low risk level, not a no risk level; no level of regular drinking has been identified as completely safe.

**How long does alcohol stay in your system?** As a rough rule the body processes about one unit an hour, but only after alcohol has been absorbed, and the rate varies with body size, sex, food, liver health and other factors. This means it cannot be used to calculate when you are safe to drive; the only reliable approach is to leave plenty of time or not drive at all.

### BMI calculator
https://hopi.co.uk/bmi-calculator/

Free BMI calculator. Enter height and weight in metric or imperial to get your body mass index and the NHS weight category, with the formula and its limits.

**What is a healthy BMI?** For most adults the NHS treats 18.5 to 24.9 as the healthy weight range. Below 18.5 is classed as underweight, 25 to 29.9 as overweight and 30 or above as obese. Lower thresholds apply for people from some ethnic backgrounds.

**How is BMI calculated?** Weight in kilograms divided by height in metres squared. If you use imperial units the tool converts first: pounds multiplied by 0.453592 gives kilograms, and inches multiplied by 0.0254 gives metres. The result is the same either way.

**Is BMI accurate for everyone?** No. It cannot tell muscle from fat, so muscular people can score high while carrying little fat, and older adults can score in range while carrying more. It is not designed for pregnancy, and children are assessed with centile charts instead. Treat it as a starting point, not a verdict.

**Why does the NHS use different thresholds for some ethnic groups?** Research shows that people from South Asian, Chinese, other Asian, Middle Eastern, Black African and African-Caribbean backgrounds face higher health risks at lower BMIs. For these groups the NHS flags increased risk from a BMI of 23 and high risk from 27.5.

**What should I do if my BMI is outside the healthy range?** A single number is not a diagnosis, so there is no need to panic either way. The NHS BMI service on nhs.uk takes more factors into account, and your GP or practice nurse can look at the fuller picture, including waist measurement and lifestyle.

### Body fat percentage calculator
https://hopi.co.uk/body-fat-calculator/

Free body fat percentage calculator using the US Navy tape method. Enter a few measurements in metric or imperial to estimate body fat, fat mass and lean mass.

**How does the US Navy body fat method work?** It estimates body fat from a handful of tape measurements: height and neck for everyone, waist for men, and waist plus hip for women. The measurements feed a formula based on logarithms that was fitted to underwater weighing results. It needs no special kit beyond a tape measure.

**How accurate is it?** It is a rough estimate. Studies put its typical error at a few percentage points against gold-standard methods, and a badly placed tape can add several more. It works best for tracking your own trend over time under the same conditions, rather than as a precise reading of a single day.

**Where do I place the tape measure?** Measure the neck just below the larynx, the waist at the navel for men and at the narrowest point for women, and the hip at the widest point. Keep the tape level and snug without squashing the skin, and measure on bare skin at the end of a normal breath for consistent results.

**What is a healthy body fat percentage?** It differs by sex and there is no single ideal. Broadly, many charts treat roughly 14 to 24% as an average range for men and 21 to 31% for women, with athletes lower and essential fat lower still. Health depends on far more than one number, so treat any band as a guide.

**How is body fat different from BMI?** BMI is only weight against height and cannot tell muscle from fat. Body fat percentage tries to estimate the fat itself, so a muscular person can have a high BMI but a low body fat figure. The two answer different questions and are best read together.

### Calories to kJ converter
https://hopi.co.uk/calories-to-kj/

Free calories to kilojoules converter. Turn kcal into kJ and back instantly using the exact factor of 4.184, with worked food-label examples.

**How many kilojoules are in a calorie?** One kilocalorie (the food calorie) is exactly 4.184 kilojoules. So a 250 kcal snack is 1,046 kJ. To go the other way, divide by 4.184: 1,000 kJ is about 239 kcal.

**Are calories and kilocalories the same thing?** On food labels, yes. The calorie people talk about in food is technically a kilocalorie, which is 1,000 of the small calories used in chemistry. Labels write it as kcal to be precise, but calorie, Calorie and kcal all mean the same unit in everyday food contexts.

**Why do UK food labels show both kJ and kcal?** UK labelling rules, carried over from EU regulations, require energy to be declared in kilojoules and kilocalories, in that order, per 100 g or 100 ml and usually per portion too. The kilojoule is the international scientific unit of energy, while the kilocalorie is the one most people actually recognise.

**What is 2,000 kcal in kilojoules?** 2,000 kcal multiplied by 4.184 is 8,368 kJ. Labels round the reference intake to 8,400 kJ, which is why you see the pair 8,400 kJ / 2,000 kcal printed on UK and EU packaging.

**Which countries use kilojoules instead of calories?** Australia and New Zealand label food energy in kilojoules, with kilocalories optional, so an Australian label might say 1,800 kJ where a UK label would lead with 430 kcal. The United States goes the other way and shows only Calories. This converter bridges all three styles.

### Daily water intake calculator
https://hopi.co.uk/water-intake-calculator/

Free daily water intake calculator. Estimate a rough daily fluid target from your weight and activity, in litres, millilitres and glasses.

**How much water should I drink a day?** There is no single right amount. The NHS suggests most adults aim for around 6 to 8 glasses of fluid a day, which includes water, lower-fat milk, tea and coffee. This tool gives a rough body-weight based figure as a starting point, but your real needs shift with heat, activity, health and diet.

**How is the estimate worked out?** It uses a common rule of thumb of about 30 to 35 millilitres of fluid per kilogram of body weight, then adds a bit for activity and hot conditions. It is a general guide only, not a medical calculation, and the range reflects how much genuine variation there is between people.

**Does tea, coffee and food count?** Yes. Most drinks count toward your fluid, and food provides a fair share too, especially fruit, vegetables, soup and yoghurt. That is one reason a pure water target can look high: you are already getting fluid from things you would not think of as a drink.

**Can you drink too much water?** Yes, though it is uncommon. Drinking very large amounts in a short time can dilute the salts in your blood, a condition called hyponatraemia, which can be dangerous. For most people, drinking to thirst and having pale straw-coloured urine is a simple, sensible guide.

**How do I know if I am drinking enough?** Thirst and the colour of your urine are the everyday signs. Pale straw colour usually means you are well hydrated, while dark yellow suggests you could drink more. Feeling thirsty, tired, lightheaded or having a dry mouth can also be signs to top up.

### Heart rate zone calculator
https://hopi.co.uk/heart-rate-zones/

Free heart rate zone calculator. Enter your age to estimate maximum heart rate and five training zones in bpm, with an optional Karvonen resting-rate method.

**How is maximum heart rate estimated?** The common shortcut is 220 minus your age, so a 30 year old gets an estimated maximum of 190 beats per minute. It is only a rough average and real maximums vary widely between people of the same age, which is why the only accurate way to know yours is a proper test.

**What are heart rate training zones for?** They split effort into bands so you can aim for the right intensity. Lower zones suit warming up, recovery and long easy sessions, middle zones build aerobic fitness, and the top zones develop speed but can only be held briefly. Spending most of your time in the easier zones is normal.

**What is the Karvonen method?** The Karvonen method uses your heart rate reserve, the gap between your resting and maximum heart rate, rather than a plain percentage of maximum. Because it factors in fitness through your resting rate, many people find its zones fit their real effort better. It needs an accurate resting heart rate to be useful.

**How do I measure my resting heart rate?** Measure it first thing in the morning before you get up, while calm and still. Count your pulse for a full minute, or use a fitness tracker averaged over several nights. For most adults it sits somewhere between 60 and 100 beats per minute, and it tends to fall as fitness improves.

**Should I train by heart rate?** It is one useful signal among several, alongside pace, breathing and how you feel. Heart rate lags behind effort, drifts up in heat and after caffeine, and monitors are not perfect, so treat the zones as a guide rather than a strict rule. If a medical condition or medication affects your heart rate, ask a doctor first.

### Pregnancy due date calculator
https://hopi.co.uk/due-date-calculator/

Free pregnancy due date calculator. Enter the first day of your last period and cycle length to estimate your due date, current week and trimester dates.

**How accurate is the estimated due date?** It is a starting point, not a promise. Only around 1 in 20 babies arrives on the due date itself, and most are born somewhere between 37 and 42 weeks. The dating scan, usually offered between 10 and 14 weeks, gives the official due date and replaces this estimate.

**Why does it count from my last period rather than conception?** Most people know the date their last period started but not the date of conception, so pregnancy is dated from the first day of the last menstrual period. That means the standard 40 weeks includes roughly 2 weeks before conception actually happened.

**What if my cycles are irregular or I am not sure of the date?** The estimate becomes less reliable, because the cycle adjustment assumes a regular pattern. Enter your best guess and treat the answer loosely. Your midwife will date the pregnancy from the scan measurement instead, which does not depend on your cycle at all.

**What do the trimester dates mean?** Pregnancy is commonly split into three trimesters: weeks 1 to 12, weeks 13 to 26, and week 27 to birth. The calculator shows the dates the second and third trimesters begin, based on your adjusted cycle. Different sources draw the lines a week or so apart, so treat them as approximate.

**Is my information stored?** No. Everything is calculated in your browser and nothing is sent to any server. Refreshing the page clears the dates.

### Running pace calculator
https://hopi.co.uk/running-pace-calculator/

Free running pace calculator. Find pace, finish time or distance from any two of them, in km or miles, with 5K, 10K, half and full marathon presets.

**How do I work out running pace?** Divide your total time by the distance. A 10 km run in 50 minutes is 3,000 seconds divided by 10, which is 300 seconds or 5 minutes per kilometre. This tool does the arithmetic and also shows the equivalent pace per mile and your speed.

**What is a good pace for a beginner?** There is no single right answer, and pace depends on age, fitness, terrain and the day. Many new runners cover a kilometre somewhere between 6 and 8 minutes and speed up as they build up. The useful comparison is with your own past runs, not with anyone else.

**What are the standard race distances?** A 5K is 5 km, a 10K is 10 km, a half marathon is 21.0975 km (13.1 miles) and a full marathon is 42.195 km (26.2 miles). The preset buttons fill these in for you so you can see the pace a target finish time needs.

**How do I convert pace per kilometre to pace per mile?** Multiply the pace per kilometre by 1.609344, since a mile is that many kilometres. A pace of 5:00 per km becomes about 8:03 per mile. The calculator shows both at once so you do not have to.

**What is the difference between pace and speed?** Pace is time per distance, such as minutes per kilometre, and gets smaller as you get faster. Speed is distance per time, such as kilometres per hour, and gets larger as you get faster. They describe the same run from opposite directions.

### Sleep cycle calculator
https://hopi.co.uk/sleep-calculator/

Free sleep cycle calculator. Enter your wake-up time to see the best bedtimes, or start from now, using 90-minute sleep cycles plus time to drop off.

**Why are sleep cycles 90 minutes?** A full cycle moves through light sleep, deep sleep and REM sleep, and in adults that journey averages about 90 minutes. It is an average, not a law: real cycles range from roughly 80 to 110 minutes and lengthen slightly through the night, so treat the suggested times as good targets rather than precision engineering.

**What if I take longer than 15 minutes to fall asleep?** The calculator assumes the average of about 15 minutes. If you know you take 30 minutes, simply head to bed 15 minutes earlier than the suggested time. Falling asleep dramatically faster than 10 minutes most nights can be a sign you are not getting enough sleep overall.

**Is 4.5 hours of sleep enough?** No, not as a routine. The 3-cycle option exists for nights when a full sleep is impossible and waking at the end of a cycle beats waking mid-cycle. The NHS advises most adults need 7 to 9 hours a night, which is the 5 or 6 cycle range.

**Why do I feel groggy even after a long sleep?** You probably woke in the middle of deep sleep. That heavy, disoriented feeling is called sleep inertia, and it depends on which stage you wake from more than on total hours. Timing sleep in whole cycles raises the odds of waking in light sleep instead.

**Do naps count as sleep cycles?** A nap either stays short or goes full cycle. Around 20 minutes keeps you in light sleep so you wake refreshed, while 90 minutes completes a whole cycle. The 30 to 60 minute middle ground often ends in deep sleep and leaves you groggier than before.

### TDEE & calorie calculator
https://hopi.co.uk/tdee-calculator/

Free TDEE calculator. Enter age, height, weight and activity to estimate your maintenance calories using the Mifflin-St Jeor formula, plus BMR and goal figures.

**What is the difference between BMR and TDEE?** BMR (basal metabolic rate) is roughly the energy your body uses at complete rest just to keep you alive. TDEE (total daily energy expenditure) is your BMR multiplied by an activity factor, so it also counts moving, working and exercising. TDEE is always the larger number.

**Which formula does this use?** The Mifflin-St Jeor equation, which research has found to be one of the more reliable estimates for the general population. It uses your weight in kilograms, height in centimetres, age and sex. Imperial entries are converted to metric first.

**How accurate is a calorie estimate?** It is an estimate, not a measurement. Real energy use varies with muscle mass, genetics, hormones, medication and how much you fidget, so two people with the same figures can differ by several hundred calories. Treat the number as a starting point and adjust based on what actually happens over a few weeks.

**What do the goal figures mean?** A rough 500 calorie daily deficit is often linked with losing about half a kilogram a week, and a 500 calorie surplus with gradual gain, because roughly 7,700 calories equals a kilogram of body fat. These are averages across a population and will not match everyone exactly.

**Is it safe to eat very few calories?** Very low intakes can leave you short of nutrients and are not suitable for everyone. The NHS suggests most adults should not drop below roughly 1,500 calories a day without medical support. If you are planning a big change to how you eat, speak to a GP or a registered dietitian first.

## Dev & data

### Base64 encode & decode
https://hopi.co.uk/base64/

Free Base64 encoder and decoder. UTF-8 safe, so accents and emoji survive the round trip, with clear errors on bad input. Runs entirely in your browser.

**Is my text uploaded anywhere?** No. Encoding and decoding happen entirely in your browser with JavaScript. Tokens, credentials and config values never leave your device, which matters because Base64 strings often contain exactly that sort of material.

**Is Base64 encryption?** No. Base64 is an encoding, not encryption. Anyone can decode it instantly with a tool like this one, so it provides no secrecy at all. Its job is to make binary data safe to carry through text-only channels, not to hide it.

**Why do some Base64 strings end in one or two equals signs?** That is padding. Base64 turns every 3 bytes into 4 characters, so when the input length is not a multiple of 3 the encoder pads the final group. One leftover byte produces two equals signs and two leftover bytes produce one.

**Why does my decode fail with an error?** The input contains characters outside the Base64 alphabet, or its length is wrong after padding. Common causes are truncated strings, URL-safe Base64 that uses minus and underscore instead of plus and slash, and stray line breaks or spaces. This tool strips whitespace for you but cannot repair a truncated string.

**Does this handle emoji and accented characters?** Yes. The text is converted to UTF-8 bytes before encoding and decoded back from UTF-8 afterwards, so characters like the pound sign, e acute and emoji survive the round trip. Older tools that skip this step corrupt anything outside basic ASCII.

### CSS minifier
https://hopi.co.uk/css-minifier/

Free CSS minifier. Strip comments and whitespace from stylesheets, with strings and calc() preserved and the bytes saved shown. Runs in your browser.

**Is my CSS uploaded anywhere?** No. Minification runs entirely in your browser with JavaScript, so stylesheets never leave your device. You can safely paste CSS from private or unreleased projects.

**Will minifying break my CSS?** This tool only removes comments and whitespace that browsers ignore, and it leaves quoted strings and the spaces inside calc() expressions alone, so valid CSS stays valid. It does not rewrite values or shorten colours, which is where aggressive minifiers occasionally introduce bugs.

**Why does calc() need its spaces?** Inside calc(), the plus and minus operators must have a space on each side, so calc(100% - 20px) is valid but calc(100%-20px) is not. A careless minifier that strips those spaces silently breaks the declaration. This tool never removes spaces around plus or minus signs, so calc() expressions pass through intact.

**How much smaller will my CSS get?** It depends on how it is written. Typical hand-written CSS with normal indentation and a sprinkling of comments shrinks by roughly 15 to 40 percent. Heavily commented files shrink more, and already compact CSS shrinks less. The before and after sizes are shown so you can see the real figure for your file.

**Is this a replacement for a build tool?** No. Build-time minifiers such as cssnano and Lightning CSS go further: they merge rules, shorten colours and values, and drop unused prefixes. This tool is for the quick case where you want a smaller stylesheet right now without installing anything. For a production pipeline, use a build tool and serve the result compressed.

### CSV to JSON converter
https://hopi.co.uk/csv-to-json/

Free CSV to JSON converter. Paste CSV, get a clean JSON array with proper handling of quoted fields. Runs entirely in your browser: nothing is uploaded.

**Is my data uploaded anywhere?** No. The conversion runs entirely in your browser with JavaScript, so exported customer lists, financial data and anything else you paste never leave your device. That is the whole point of doing it client side.

**How are commas inside values handled?** The parser follows the standard CSV quoting rules. A field wrapped in double quotes can contain commas and even line breaks, and a double quote inside a quoted field is written as two double quotes. All of that is unwrapped correctly rather than split naively on every comma.

**What does the first row is headers option do?** When ticked, the values in the first row become the keys of each JSON object, so a name column produces objects with a name property. When unticked, every row including the first becomes a plain array of strings, which suits files that have no header row.

**Why are all my numbers in quotes in the output?** CSV has no types, so every field arrives as text and the converter keeps it as a string rather than guessing. Guessing goes wrong quickly: phone numbers lose leading zeros and product codes like 1e5 turn into 100000. If you want real numbers, convert the specific fields you trust after parsing.

**My file uses semicolons instead of commas. Why?** Spreadsheet software in many European locales exports with semicolon separators because the comma is used as the decimal mark. This tool expects genuine comma-separated values, so either re-export with commas or do a careful find and replace first, watching out for semicolons inside quoted text.

### Cron expression translator
https://hopi.co.uk/cron-expression-parser/

Free cron expression translator. Turn five-field cron schedules into plain English, with steps, ranges, lists and names all understood. Runs in your browser.

**What do the five fields mean?** In order: minute (0 to 59), hour (0 to 23), day of month (1 to 31), month (1 to 12), and day of week (0 to 7, where both 0 and 7 mean Sunday). A star in a field means every value. The translator labels each field for you so you can see which is which.

**What does */5 mean?** It is a step: every fifth value. In the minute field, */5 means minutes 0, 5, 10 and so on, so the job runs every 5 minutes. Steps can also apply to a range, so 0-20/2 in the hour field means every 2nd hour from 0 through 20.

**What happens when both day-of-month and day-of-week are set?** In standard cron they are combined with OR, not AND. The expression 0 0 1 * 1 runs at midnight on the 1st of the month and also every Monday, which surprises almost everyone. If you want the first Monday of the month you need extra logic in the job itself.

**Can I use names instead of numbers?** Yes. Months can be written as three-letter names such as JAN or aug, and days of the week as SUN through SAT, in either case. Names work as single values and in ranges and lists, so MON-FRI is a valid day-of-week field.

**Which time zone does cron use?** Whatever the machine running the cron daemon is set to, which on servers is usually UTC. A schedule of 0 9 * * * fires at 09:00 server time, not your local time, so a UK job on a UTC server drifts by an hour when British Summer Time starts. Check the server clock before trusting a schedule.

### Diff checker
https://hopi.co.uk/diff-checker/

Free online diff checker. Paste two versions of your text and see added and removed lines highlighted instantly. Runs in your browser, nothing is uploaded.

**Is my text uploaded anywhere?** No. The comparison runs entirely in your browser with JavaScript. Neither version of your text is uploaded, stored or seen by anyone, which makes it safe to compare contracts, code or anything else confidential.

**How does the comparison actually work?** The tool splits both texts into lines and finds the longest common subsequence, the longest run of lines the two versions share in the same order. Everything outside that shared backbone is reported as added or removed. It is the same idea used by version control tools such as Git.

**Why does an edited line show as one removed plus one added?** The comparison works line by line, so a line that changed is treated as the old line going and a new line arriving. That pairing of a red line and a green line next to each other is the standard way diffs show an edit.

**Does the diff ignore spaces or capitalisation?** No. Two lines only count as the same if they match exactly, including spaces, tabs and case. If stray whitespace is creating noise, tidy both versions with the remove extra spaces tool first and then compare them.

**Is there a limit on how much text I can compare?** For very large texts, roughly a couple of thousand changed lines on each side, the tool will ask you to compare smaller sections instead. Unchanged beginnings and endings are skipped efficiently, so long documents with few edits compare without any trouble.

### Dummy data generator
https://hopi.co.uk/dummy-data-generator/

Free dummy data generator. Create fake but safe UK test records with names, emails and phone numbers that can never reach a real person. CSV or JSON.

**Can the phone numbers ever ring a real person?** No. Every number comes from ranges Ofcom has reserved for TV and radio drama, such as 07700 900000 to 900999 for mobiles and blocks like 0113 496 0000 to 0999 for landlines. Ofcom keeps these ranges out of normal allocation, so no communications provider can issue them to a real customer.

**Why do all the emails end in example.com or example.org?** Those domains are reserved by the internet standards body under RFC 2606 specifically for documentation and testing. They are guaranteed never to belong to a real company or accept real mailboxes, so if your test system accidentally sends an email, it cannot land in anyone's inbox.

**Could a generated record match a real person by accident?** A name might, because the lists use common UK names and a random pairing can coincide with somebody real. Nothing else will: the phone numbers, emails and full record combinations are synthetic, so no generated row describes an actual person or lets anyone contact one.

**Is dummy data safer than testing with real customer data?** Much safer. Real customer records in a test database are still personal data under UK GDPR, with all the security, access and retention duties that brings, and a leaked staging server becomes a real breach. Synthetic records carry none of that risk because there is nobody to harm.

**How is the CSV formatted?** The first line holds snake_case column headers, one row follows per record, and any value containing a comma, quote or line break is wrapped in double quotes with inner quotes doubled, per RFC 4180. Dates of birth use the ISO YYYY-MM-DD format, which spreadsheets and databases both import cleanly.

### Email link generator
https://hopi.co.uk/email-link-generator/

Free mailto link generator. Build an email link with to, cc, bcc, subject and body, correctly percent-encoded, plus an HTML snippet and a test link.

**Why do spaces become %20 rather than a plus sign?** The plus-for-space convention belongs to web form submissions, not mailto links. Mail clients are not required to translate a plus back into a space, so a subject encoded with plus signs can arrive reading like Hello+there. Percent-encoding spaces as %20 works everywhere, which is why this tool uses it.

**How do I put line breaks in the body?** Just press Enter in the body field. Each line break is encoded as %0D%0A, the carriage return and line feed pair the mailto standard expects, so the message opens in the mail app with your paragraphs intact. Typing %0D%0A by hand into the raw URL works too.

**Can a mailto link add an attachment?** No. The mailto standard has no attachment mechanism, and for good reason: a web page should not be able to reach into someone's files. If you need people to send you a file, ask for it in the body text or use a proper upload form instead.

**How do I send to more than one address?** Separate addresses with commas in the to, cc or bcc fields and the tool joins them correctly. Be careful with bcc: some mail clients ignore the bcc part of a mailto link entirely, so do not rely on it for anything important.

**Is anything I type here uploaded?** No. The link is assembled entirely in your browser with JavaScript, so addresses, subjects and body text never leave your device. Clicking the test link simply hands the finished mailto URL to your own mail app.

### HTML escape & unescape
https://hopi.co.uk/html-escape/

Free HTML escape and unescape tool. Convert special characters to entities for safe display, or decode entities back to text. Runs entirely in your browser.

**Which characters does escaping convert?** The five with special meaning in HTML: the ampersand becomes &, the less-than sign becomes <, the greater-than sign becomes >, the double quote becomes " and the single quote becomes '. Everything else passes through unchanged.

**Why do the quotes need escaping too?** Angle brackets and ampersands matter anywhere in HTML, but quotes matter inside attribute values. If user text goes into something like a title or value attribute, an unescaped quote can end the attribute early and let the rest of the text act as markup. Escaping all five characters is safe in every position.

**Does escaping user input prevent XSS?** It is the core defence for text placed into HTML, yes. Escaping means a pasted script tag displays as text instead of running. But context matters: text going into a URL, a style block or a script block needs different handling, and frameworks like React escape output for you by default.

**Will unescape run scripts from the text I paste?** No. Decoding happens inside a detached textarea element that is never added to the page, and a textarea treats its content as plain text, so nothing is executed or rendered. It simply converts entities like & and £ back into characters.

**Is my text uploaded anywhere?** No. Both directions run entirely in your browser with JavaScript, so snippets, templates and user data never leave your device.

### HTML text & link extractor
https://hopi.co.uk/html-text-extractor/

Free HTML text extractor. Paste HTML to pull out the plain text, links, email addresses, image sources and headings. Runs in your browser, nothing uploaded.

**Why paste HTML instead of just giving a web address?** Browsers deliberately block one website from fetching the raw source of another, a rule called the same-origin policy, so a page like this cannot reach out and download another site for you. Pasting the HTML you already have is the workable way around that. Open the page, view its source, copy it and paste it here.

**How do I get a page's HTML?** In most desktop browsers press Ctrl and U, or right-click the page and choose View page source, then select all and copy. For an email, use the Show original or View source option in your mail client. Paste whatever you copied into the box.

**Is my HTML uploaded anywhere?** No. The parsing and extraction happen entirely in your browser with JavaScript. Nothing you paste leaves your device, and refreshing the page clears it, so it is safe to use with private pages and email source.

**Why are some links missing or shown as relative paths?** The extractor reads the links exactly as they appear in the source you paste. Relative paths like /contact stay relative because that is how they were written. Links that a page builds with JavaScript after it loads are not in the raw source, so they will not appear unless you copy the source after the page has finished rendering.

**Does it run any scripts in the HTML I paste?** No. The HTML is parsed into an inert document, which means script tags are read as text and never executed. Every piece of extracted content is placed on the page as plain text, so nothing in what you paste can run or change this page.

### HTTP status code reference
https://hopi.co.uk/http-status-codes/

Free HTTP status code reference. Search every standard code from 100 to 511, grouped 1xx to 5xx, with plain-English meaning and when to use each one.

**What do the five classes mean?** The first digit sets the class. 1xx is informational, 2xx means success, 3xx is a redirect, 4xx is a client error where the request was at fault, and 5xx is a server error where the server failed to handle a valid request. Knowing the class alone tells you which side of the connection to look at first.

**What is the difference between 401 and 403?** A 401 Unauthorized means you have not proven who you are, so authentication is missing or wrong and retrying with valid credentials might work. A 403 Forbidden means the server knows who you are and still refuses, so no amount of logging in will help. In short, 401 is who are you, 403 is you are not allowed.

**Should a redirect be 301 or 302?** Use 301 Moved Permanently when a page has a new home for good, because browsers and search engines cache it and pass on ranking. Use 302 Found, or 307 Temporary Redirect, when the move is temporary and you want clients to keep asking the original address. Getting this wrong can strand your SEO on a URL you meant to abandon.

**Is 418 I'm a teapot real?** Yes, in a manner of speaking. It began as an April Fools joke in 1998 and was never meant for real servers, but it is written down in RFC 2324 and many frameworks still support it. You will occasionally see it used as a playful way to refuse a request.

**Are these all the codes that exist?** This lists the standard codes registered with the IANA, which is what you will meet across the web. Individual servers and platforms sometimes invent their own numbers in the same ranges, such as some 5xx codes used by particular CDNs, but those are not part of the standard and are documented by the vendor.

### Hash generator
https://hopi.co.uk/hash-generator/

Free SHA-256, SHA-1 and SHA-512 hash generator. Type or paste text and get the hex digest instantly. Runs entirely in your browser: nothing is uploaded.

**Is my text uploaded anywhere?** No. Hashing runs entirely in your browser using the WebCrypto API built into every modern browser. Nothing you type is sent to a server, which makes the tool safe to use with tokens, keys and anything else you would rather keep private.

**Why is there no MD5 option?** MD5 has been broken since 2004: researchers can manufacture two different inputs that share the same MD5 hash, which defeats the whole point of a hash. Browsers agree, so the WebCrypto API does not even implement it. If a system forces you to use MD5, treat that as a sign the system needs updating.

**Can I reverse a hash back to the original text?** Not directly. Hash functions are one way, so there is no formula that turns a digest back into its input. The caveat is short or common inputs: attackers can hash millions of guesses and compare, which is why single dictionary words make weak passwords no matter how strong the hash is.

**Should I use SHA-1 for anything new?** No. Practical collision attacks against SHA-1 were demonstrated in 2017, and browsers and certificate authorities have dropped it. It is included here because plenty of older systems, checksums and git repositories still show SHA-1 values you may need to reproduce or compare.

**Is SHA-256 the right way to store passwords?** No. Plain SHA-256 is deliberately fast, which lets attackers test billions of guesses per second against stolen hashes. Password storage needs a slow, salted algorithm designed for the job, such as bcrypt, scrypt or Argon2. Use SHA-256 for integrity checks and fingerprints, not for passwords.

### Inline CSS converter
https://hopi.co.uk/inline-css-converter/

Free inline CSS converter for HTML email. Moves style block rules onto matching elements as inline styles, entirely in your browser. Nothing is uploaded.

**Why do email templates need inline CSS?** Email clients are far less predictable than browsers. Desktop Outlook renders HTML with Word's engine and ignores much embedded CSS, some webmail clients strip the head of a message along with any style blocks, and forwarding often does the same. A style written directly on the element in a style attribute travels with the element, so it survives almost everywhere.

**Is my HTML uploaded anywhere?** No. Parsing, matching and rewriting all happen in your browser with JavaScript. Your templates, copy and links never leave your device, so it is safe to use with unreleased campaigns and client work.

**What happens to hover styles and media queries?** They cannot be expressed as inline styles, so they are never inlined. Media queries are kept in a small retained style block by default, which modern clients such as Apple Mail and Gmail respect. Pseudo-class and pseudo-element rules like a:hover or .btn::after are skipped and listed in the report so you know exactly what was left out.

**Does the converter change my HTML structure?** The document is parsed with your browser's own HTML parser, styles are applied, and the result is serialised back. Elements, attributes, text and order are preserved, though minor normalisation can occur, for example attribute quoting or the repair of unclosed tags, exactly as a browser would repair them.

**Should I strip class attributes after inlining?** Once every rule is inlined the classes usually do nothing, and removing them shrinks the message, which helps you stay under Gmail's clipping limit. Keep them if your retained media queries still target those classes, or if your sending platform uses them for link tracking or editing.

### JSON formatter
https://hopi.co.uk/json-formatter/

Free JSON formatter and validator. Pretty print or minify JSON instantly with clear error messages. Runs entirely in your browser: nothing is uploaded.

**Is my JSON uploaded anywhere?** No. Formatting and validation happen entirely in your browser with JavaScript. Your data never leaves your device, which makes this safe to use with API responses and config files you would not paste into an unknown website.

**Why does a trailing comma break my JSON?** The JSON specification does not allow a comma after the last item in an object or array, even though JavaScript itself tolerates it. Deleting the final comma before a closing bracket or brace fixes the most common JSON error there is.

**Can I use single quotes in JSON?** No. JSON requires double quotes around both keys and string values. Single quotes are valid in JavaScript objects but not in JSON, which is a stricter format.

**What does an error like Unexpected token mean?** The parser met a character it could not accept at that position: often a missing comma, an unquoted key, a stray bracket or a trailing comma. The error message includes the position, and formatting progressively smaller chunks of the document is the quickest way to corner the culprit.

**Does formatting change my data or reorder keys?** No. Pretty printing and minifying only change whitespace. Key order, values and structure all stay exactly as they were.

### JSON to CSV converter
https://hopi.co.uk/json-to-csv/

Free JSON to CSV converter. Paste a JSON array of objects and get clean, properly quoted CSV to download or copy. Runs in your browser: nothing is uploaded.

**What shape does my JSON need to be?** A single array whose items are objects, like a list of records. The keys of those objects become the column headers and each object becomes one row. A bare object on its own does not work, but wrapping it in square brackets to make a one item array does.

**What happens if my objects have different keys?** The converter takes the union of every key it sees, in the order they first appear, and uses that as the header row. Any object missing one of those keys simply gets an empty cell in that column, so no data is dropped and no column is guessed away.

**How are nested objects and arrays handled?** A CSV cell can only hold text, so any value that is itself an object or an array is written back out as compact JSON inside that one cell. That keeps the structure recoverable, though most people flatten nested data before converting if they want it spread across columns.

**Are commas and quotes inside values safe?** Yes. The output follows RFC 4180, the closest thing CSV has to a standard. Any value containing a comma, a double quote or a line break is wrapped in double quotes, and quotes inside it are doubled, so nothing splits a field in half when the file is opened later.

**Is my data uploaded anywhere?** No. The whole conversion runs in your browser with JavaScript, so API responses, exports and anything else you paste never leave your device. That is why it works offline once the page has loaded.

### JWT decoder
https://hopi.co.uk/jwt-decoder/

Free JWT decoder. See a token's header, payload and expiry as readable dates, decoded instantly in your browser. Nothing is uploaded, nothing is stored.

**Is my token uploaded anywhere?** No. The token is decoded with JavaScript in your browser and never leaves your device. That makes it safe to inspect real tokens from live systems, although it is still good practice to rotate any credential you have been pasting around while debugging.

**Does this tool verify the signature?** No, and this matters. It only decodes what the token says about itself. Anyone can create a token with any payload they like, so a decoded claim proves nothing until a server checks the signature against the correct secret or public key.

**What are exp, iat and nbf?** They are registered time claims, each a Unix timestamp in seconds. The exp claim is when the token expires, iat is when it was issued, and nbf is the moment before which it must not be accepted. This tool converts all three to readable dates and compares exp against your device clock.

**Why does my token fail to decode?** A JWT must be three base64url sections separated by dots, with the first two containing JSON. Extra whitespace and a leading Bearer prefix are handled for you, but truncated tokens, five-section encrypted JWEs and opaque session identifiers that merely look like tokens will all fail.

**Can anyone read a JWT?** Yes. Base64url is an encoding, not encryption, so anyone who holds the token can read the header and payload in full. Never put passwords, card numbers or other secrets in a JWT payload, and treat the token itself as a credential to be kept private.

### Markdown previewer
https://hopi.co.uk/markdown-previewer/

Free markdown previewer. Type markdown and see headings, lists, links and code render live as you type. Everything runs in your browser, nothing is uploaded.

**Which markdown features are supported?** Headings from # to ###, bold with double asterisks, italic with single asterisks or underscores, links, inline code in backticks, fenced code blocks, bulleted and numbered lists, and blockquotes. That covers the everyday markdown used in READMEs, issues and comments.

**Why does my HTML show as plain text instead of rendering?** That is deliberate. Every character you type is escaped before any markdown is applied, so raw HTML tags are displayed rather than executed. It means nothing you paste can run scripts or inject markup into the page, which keeps the preview safe.

**Is my markdown uploaded anywhere?** No. The conversion from markdown to the preview happens entirely in your browser with JavaScript. Nothing you type or paste leaves your device, and refreshing the page clears it.

**Why is my link not clickable in the preview?** Only links whose address starts with http, https or mailto are turned into real links. Anything else, including javascript addresses, is rendered as plain text as a safety measure. Check the address starts with https:// and uses the [text](address) format with no space between the bracket and the parenthesis.

**Is this full CommonMark?** No, it is a deliberately small, safe subset. Tables, images, footnotes, nested lists and raw HTML are not rendered. If a document leans on those features, preview it in the tool where it will finally live, such as GitHub or your CMS.

### Meta tag generator
https://hopi.co.uk/meta-tag-generator/

Free meta tag generator. Build title, description, canonical, Open Graph and Twitter card tags with live character counts. Runs entirely in your browser.

**Do meta tags boost my search rankings?** Not directly. The meta description has not been a ranking factor for many years, and the keywords tag is ignored entirely. What these tags do is help search engines and social platforms understand and present your page: a clear title and description can earn more clicks from the same position, which is valuable, but the tags alone do not move you up the results.

**How long should a page title be?** Around 60 characters is the working guideline. Google actually truncates by pixel width rather than a strict character count, so 60 is an approximation, but titles under that length almost always display in full. Put the important words first so they survive if the end is cut.

**What are Open Graph tags?** They control how a link looks when shared on Facebook, LinkedIn, WhatsApp and most messaging apps: the headline, description and preview image. Without them the platform guesses from the page content, and the guess is often wrong or ugly. Twitter reads its own twitter: tags first but falls back to Open Graph for most values.

**Should I use summary or summary_large_image?** Use summary_large_image if you have a decent landscape image, because the preview is much bigger and more clickable. The plain summary card shows a small square thumbnail beside the text, which suits logos and profile pages better than article images.

**Is anything I type uploaded?** No. The snippet is built entirely in your browser with JavaScript, so titles, descriptions and URLs never leave your device.

### Number base converter
https://hopi.co.uk/number-base-converter/

Free number base converter. Switch between binary, octal, decimal and hexadecimal instantly, or turn text into UTF-8 binary and back. Nothing is uploaded.

**How do I convert decimal to binary by hand?** Divide by 2 repeatedly and keep the remainders. For 13: 13 divided by 2 is 6 remainder 1, then 3 remainder 0, then 1 remainder 1, then 0 remainder 1. Read the remainders bottom to top and you get 1101.

**Why do programmers use hexadecimal?** One hex digit represents exactly four bits, so a byte is always two hex digits. That makes hex a compact, lossless shorthand for binary: 11111111 becomes FF. You see it in colour codes, memory addresses, MAC addresses and hash outputs.

**How large a number can the converter handle?** Effectively unlimited. It uses JavaScript's BigInt arithmetic, which works with whole numbers of any size, so values far beyond the usual 64-bit ceiling convert exactly with no rounding.

**How does text to binary work?** Each character is encoded as UTF-8 bytes and each byte is shown as an 8-digit binary octet. Plain English letters take one octet each, so Hi becomes 01001000 01101001, while accented characters, symbols and emoji take two to four octets.

**Is anything I type uploaded?** No. All conversion happens in your browser with JavaScript, and nothing is sent to a server. That makes it safe to use with values from private code, logs or documents.

### Password strength checker
https://hopi.co.uk/password-strength-checker/

Free password strength checker. Get an entropy estimate, a crack-time guess and pattern warnings, all worked out in your browser. Nothing is ever uploaded.

**Is my password sent anywhere?** No. Every part of the check runs in JavaScript on your own device. Nothing you type is uploaded, logged or stored, and leaving the page clears it. This is deliberately unlike sites that ask you to submit a password to test it, which you should never do.

**How is the strength score worked out?** It estimates entropy, the number of guesses an attacker would need, from the size of the character set you used and the length of the password. It then subtracts for patterns that make guessing easier, such as dictionary words, sequences like 123, repeated characters and keyboard walks.

**What does the crack time mean?** It is a rough estimate of how long an offline attacker with fast hardware, assumed here at ten billion guesses a second, would take on average. Online attacks against a login form are far slower, but you should plan for the offline case because that is what happens when a site is breached.

**Why is my clever password rated weak?** Human tricks are predictable. Swapping a for @, adding a 1 on the end, or basing a password on a word, a name or a keyboard row are all in every attacker's dictionary. The tool flags these because a machine tries them first, long before it resorts to brute force.

**What should I do instead?** Use a long, random password, sixteen characters or more, and let a password manager generate and remember it. The linked password generator makes one in your browser. Length beats cleverness, and a unique password per site limits the damage when any one site is breached.

### Regex tester
https://hopi.co.uk/regex-tester/

Free online regex tester. Test a pattern with g, i and m flags against your text and see every match with its position instantly. Nothing is uploaded.

**Is my pattern or test text uploaded anywhere?** No. The pattern runs against your text entirely in your browser using JavaScript's built-in regular expression engine. Nothing you type is uploaded, stored or seen by anyone, so it is safe to test against logs, emails or code.

**What do the g, i and m flags do?** The g flag finds every match rather than stopping at the first. The i flag ignores case, so cat matches Cat and CAT. The m flag makes the ^ and $ anchors match at the start and end of every line instead of only the whole text.

**Why does my pattern show as invalid?** The pattern breaks a rule of regular expression syntax, most often an unclosed bracket or group, or a quantifier like + with nothing before it. The error message under the pattern box names the problem. To match a special character literally, put a backslash before it.

**Why does the dot not match my line breaks?** In JavaScript the dot matches any character except a line break by default. If you need to cross lines, match the break explicitly with something like [\s\S], which means any whitespace or non-whitespace character.

**Which flavour of regex does this use?** It uses JavaScript's RegExp engine, the same one that runs in every browser and in Node.js. Core syntax matches other flavours such as PCRE and Python, but some advanced features differ, so always test patterns in the environment where they will run.

### Robots.txt generator
https://hopi.co.uk/robots-txt-generator/

Free robots.txt generator. Build a robots.txt file from presets or custom allow and disallow rules, add a sitemap line, then download it. Runs in your browser.

**Does robots.txt stop a page appearing in Google?** No, and this catches a lot of people out. Robots.txt stops compliant crawlers fetching a page, but if other sites link to that page it can still be indexed and appear in results as a bare URL with no description. To keep a page out of the index, let it be crawled and add a noindex robots meta tag, or put it behind a login.

**Is robots.txt a security measure?** No. The file is public, so anyone can read yours at your domain followed by /robots.txt, which means listing a private path actually advertises it. Well-behaved crawlers follow the rules; scrapers and attackers simply ignore them. Anything genuinely sensitive needs authentication, not a polite request.

**Does the crawl-delay directive work?** Not for Google, which has never supported crawl-delay and ignores the line entirely. Bing and Yandex do respect it, which is how the myth survives. If Googlebot is hitting your server too hard, the supported routes are Search Console's crawl rate tools and returning 503 or 429 responses when you are overloaded.

**Where does the file go?** At the root of the host, so https://example.co.uk/robots.txt, with the filename in lowercase. Each subdomain needs its own file, because the one on www.example.co.uk does not cover shop.example.co.uk. Crawlers only ever look at the root, so a robots.txt in a subfolder does nothing.

**Is anything I type uploaded?** No. The file is built entirely in your browser with JavaScript and downloaded straight from it, so your rules and sitemap URL never leave your device.

### SEO meta tag analyser
https://hopi.co.uk/seo-analyzer/

Free SEO analyser. Paste a page's HTML to check the title, meta description, headings, canonical, Open Graph and more. Runs entirely in your browser.

**Does passing every check guarantee a higher ranking?** No, and no tool can promise that. These checks cover the tags and structure that help search engines and social platforms understand and present your page. Getting them right removes avoidable problems and can earn more clicks, but ranking depends on content quality, links, site speed and much more that no meta tag controls.

**What is the ideal title and description length?** A title of roughly 50 to 60 characters almost always shows in full, and a meta description of around 150 to 160 characters fills the snippet without being cut off. Google actually truncates by pixel width rather than a strict count, so treat these as guidelines, and put the important words first so they survive if the end is trimmed.

**Are multiple H1 headings really a problem?** Modern search engines cope with more than one H1, so it is rarely fatal. The convention of a single, clear H1 per page still helps because it states plainly what the page is about, for readers, for screen readers and for crawlers. The analyser flags a count other than one so you can make a deliberate choice.

**What are Open Graph and Twitter card tags?** Open Graph tags control how your link looks when shared on Facebook, LinkedIn, WhatsApp and most messaging apps: the headline, description and preview image. Twitter, now X, reads its own twitter tags first and falls back to Open Graph. Without them the platform guesses from the page, and the guess is often wrong or ugly.

**Is my HTML uploaded anywhere?** No. The page is parsed and checked entirely in your browser with JavaScript, so the HTML you paste never leaves your device. That makes it safe to run against staging pages and internal sites that are not public yet.

### SQL formatter
https://hopi.co.uk/sql-formatter/

Free SQL formatter. Uppercase keywords, put each clause on its own line and indent conditions, with strings preserved. Runs entirely in your browser.

**Is my SQL uploaded anywhere?** No. Formatting runs entirely in your browser with JavaScript, so queries never leave your device. That makes it safe to tidy queries containing real table names, schema details and literal values from production systems.

**Will formatting change what my query does?** No. The formatter only changes whitespace and the case of keywords. Quoted strings, quoted identifiers, numbers, comments and the order of every token are preserved, so the query means exactly what it meant before, just laid out readably.

**Why are my column names not uppercased?** Only words on the formatter's keyword list are uppercased, so identifiers such as table and column names keep the case you wrote them in. A column that happens to be named like a keyword, for example one called count, will be uppercased too; quote such identifiers and they are left completely alone.

**Which SQL dialects does this work with?** The layout rules cover the shared core of SELECT, INSERT, UPDATE and DELETE statements, which is common to PostgreSQL, MySQL, SQL Server, SQLite and most other dialects. Single quotes with doubled escapes, double-quoted and backtick-quoted identifiers, and both comment styles are all understood. Dialect-specific syntax passes through unformatted rather than breaking.

**Does it validate my SQL?** No. It is a formatter, not a parser, so it will happily lay out a query with a typo in it. Syntax errors only surface when the database itself runs the query. For checking logic, formatting still helps, because a wrongly placed condition is far easier to spot at one clause per line.

### Schema markup generator
https://hopi.co.uk/schema-markup-generator/

Free schema markup generator. Build valid JSON-LD for FAQ, article, local business and breadcrumb structured data, ready to paste. Runs in your browser.

**What is JSON-LD?** JSON-LD is Google's preferred format for structured data: a small script block of JSON, placed anywhere in the page, that describes the content using the schema.org vocabulary. Unlike older formats such as microdata it does not touch your visible HTML at all, which is why it is by far the easiest format to add and maintain.

**Will schema markup improve my rankings?** Not by itself, and Google says as much. Structured data helps search engines understand what a page contains and makes it eligible for rich results such as breadcrumb trails or article details. Eligibility is the key word: Google decides whether to show anything extra, and markup alone does not move you up the results.

**Where do I paste the generated code?** Anywhere in the page's HTML, though the head element is the usual home. Paste the whole snippet including the script tags. You can have several JSON-LD blocks on one page, for example breadcrumbs plus an article, each in its own script tag.

**Why does my FAQ markup not produce dropdowns in Google?** Since 2023 Google has restricted FAQ rich results to a small set of authoritative government and health sites, so most sites no longer get the expanding answers in search results. The markup is still valid and can still help search engines understand the page, but do not expect the visual treatment.

**Is my content uploaded anywhere?** No. The JSON-LD is built entirely in your browser with JavaScript, so questions, addresses and everything else you type never leave your device.

### Slug generator
https://hopi.co.uk/slug-generator/

Free slug generator. Turns any title into a clean lowercase URL slug, stripping accents and punctuation and collapsing spaces to hyphens. Runs in your browser.

**What exactly does the generator change?** It lowercases the text, converts accented letters to their plain equivalents (so cafe with an e acute becomes cafe), replaces every run of spaces, punctuation and other symbols with a single hyphen, and trims any hyphens left at the ends. Letters and digits are the only characters that survive.

**Why hyphens rather than underscores?** Search engines treat a hyphen as a word separator but treat an underscore as joining two words together, so red-wine is read as two words while red_wine can be read as one. Hyphens are also easier to see in a link, where an underscore can vanish under the underline.

**How long should a slug be?** Three to six meaningful words is a good target. Keep the words people would search for and drop filler like a, the and of. Short slugs are easier to read, share and type, and they survive redesigns better than dates and category paths baked into the URL.

**What happens to characters like the ampersand or the pound sign?** Symbols with no letter equivalent are treated as separators, so a title containing an ampersand between fish and chips becomes fish-chips. If the symbol matters to the meaning, type the word out instead, giving fish-and-chips.

**Is my text uploaded anywhere?** No. The slug is generated in your browser as you type and nothing leaves your device.

### URL encode & decode
https://hopi.co.uk/url-encoder/

Free URL encoder and decoder. Percent-encode a query value or a whole URL, or decode one back to readable text. Runs entirely in your browser, nothing uploaded.

**What is the difference between the component and whole URL modes?** Component mode encodes everything that has special meaning in a URL, including slashes, question marks and ampersands, so it is right for a single value such as a query parameter. Whole URL mode leaves the structural characters alone and only encodes what cannot appear in a URL at all, such as spaces, so an existing address keeps working.

**Why did encoding break my URL?** Almost certainly because a full URL went through component mode, which encodes the slashes and question mark that hold the address together. Use whole URL mode for complete addresses and component mode only for individual values.

**What does %20 mean?** It is a percent-encoded space: a percent sign followed by the byte value in hexadecimal. Spaces are not allowed in URLs, so they travel as %20. Every encoded character follows the same pattern, such as %26 for an ampersand and %C3%A9 for e acute, which is two bytes in UTF-8.

**Why does decoding sometimes show an error?** A percent sign in the input is not followed by two valid hexadecimal digits, so the string is malformed. This usually means the text was truncated, or it contains a literal percent sign that was never encoded. Encode the percent sign itself as %25 to fix the source.

**Is anything I paste here uploaded?** No. Encoding and decoding run entirely in your browser with JavaScript, so URLs, tokens and query strings never leave your device.

### URL parser
https://hopi.co.uk/url-parser/

Free URL parser. Split any URL into protocol, host, port, path and fragment, with query parameters decoded into a readable table. Runs in your browser.

**Is the URL I paste sent anywhere?** No. Parsing happens in your browser using the URL interface built into it, and nothing is requested, fetched or logged. That matters because URLs often contain session tokens, email addresses and other identifying values in their query strings.

**Why does my URL fail to parse?** The most common reason is a missing scheme: www.example.com is not a complete URL until it starts with https:// or similar. The tool adds https:// for you when the input looks like a bare domain and tells you it has done so. Genuinely malformed input, such as stray spaces or brackets, is reported as invalid.

**What is the difference between the host and the domain?** The host is the full name in the URL, such as shop.example.co.uk, and it can include a port. The registrable domain is the part you actually buy, example.co.uk here, and everything in front of it is a subdomain chosen by the site owner.

**Why is the port often empty?** Each scheme has a default port, 443 for https and 80 for http, and browsers omit it from the URL when the default is used. A visible port such as :8080 simply means the server listens somewhere non-standard, which is common in development.

**Are query parameters case sensitive?** Treat them as if they are. The standard leaves it to each site, and most servers and frameworks match parameter names exactly, so Page=2 and page=2 can behave differently. Hosts are the exception: domain names are case insensitive, so EXAMPLE.com and example.com are the same site.

### UTM link generator
https://hopi.co.uk/utm-link-generator/

Free UTM link generator. Tag any URL with utm_source, utm_medium and utm_campaign for GA4, keeping existing parameters intact. Runs in your browser.

**Which UTM parameters do I actually need?** Source, medium and campaign are the core trio, and GA4 expects all three to make sense of a link. Term and content are optional refinements: term for paid keywords and content for telling two links in the same campaign apart, such as a button versus a text link.

**Does capitalisation matter in UTM values?** Yes. GA4 treats values as case-sensitive, so Email, email and EMAIL show up as three separate rows in your reports and split your numbers between them. Pick lowercase for everything and stick to it, which is why this tool warns you when it spots mixed case.

**Will tagging break a URL that already has parameters?** Not here. The tool parses your URL properly and appends the UTM parameters after whatever is already in the query string, so a link like example.co.uk/page?ref=x keeps its ref parameter. Bolting UTM text on by hand with a second question mark is what breaks URLs.

**Should I tag links between pages on my own site?** No. UTM parameters are for inbound links from elsewhere, such as newsletters, ads and social posts. Tagging internal links restarts the visitor's session attribution, so the campaign that genuinely brought them to your site gets overwritten by your own navigation.

**Is my URL uploaded anywhere?** No. The link is built entirely in your browser with JavaScript, so campaign URLs, parameter values and anything else you type never leave your device.

### UUID generator
https://hopi.co.uk/uuid-generator/

Free UUID generator. Create 1 to 100 random version 4 UUIDs from your browser's cryptographic random source, then copy them all in one click. Nothing uploaded.

**What is a version 4 UUID?** A universally unique identifier built almost entirely from random bits. Of its 128 bits, 6 are fixed to mark the version and variant, leaving 122 random bits. It is the most common UUID version because it needs no central authority, no clock and no hardware address, just a good source of randomness.

**Are these UUIDs really unique?** Not guaranteed, but collisions are so unlikely they are ignored in practice. There are about 5.3 undecillion possible v4 UUIDs, and you would need to generate roughly 2.7 quintillion of them before a duplicate became more likely than not. Every database and cloud platform in production relies on those odds.

**How random are they?** The tool uses crypto.randomUUID where the browser provides it, falling back to crypto.getRandomValues, both of which draw from the operating system's cryptographically secure random source. It never uses Math.random, which is predictable and unsuitable for identifiers.

**Why do all the UUIDs have a 4 in the same place?** The 13th hexadecimal digit is the version field, so every version 4 UUID shows a 4 there. The 17th digit is the variant field and is always 8, 9, a or b. Those are the only positions that are not random.

**Are the UUIDs generated on a server?** No. They are generated in your browser using its own random source, and nothing is sent or stored anywhere. Refreshing the page produces a completely fresh, unrecorded set.

### Unix timestamp converter
https://hopi.co.uk/unix-timestamp-converter/

Free Unix timestamp converter. Turn epoch timestamps into readable dates and dates into timestamps, with seconds and milliseconds detected automatically.

**What is the Unix epoch?** The epoch is midnight UTC on 1 January 1970, the zero point that Unix systems count from. A Unix timestamp is simply the number of seconds since that moment, which makes date arithmetic and comparisons trivial for computers even though the raw number means little to people.

**How does the tool know whether I pasted seconds or milliseconds?** By size. Timestamps in seconds are currently 10 digits long, while millisecond timestamps are 13 digits. The tool treats any value of 100,000,000,000 or more as milliseconds, and it always tells you which unit it detected so you can override by dividing or multiplying by 1,000.

**Do timestamps depend on my time zone?** No. A Unix timestamp identifies one exact instant everywhere on Earth, always counted in UTC. Time zones only affect how that instant is displayed, which is why this tool shows you both the UTC reading and the same moment in your local time.

**What is the year 2038 problem?** Systems that store timestamps as signed 32-bit integers run out of room at 2,147,483,647, which lands at 03:14:07 UTC on 19 January 2038. One second later the value overflows and wraps to 1901. Modern 64-bit systems are unaffected, but old embedded devices and file formats can still be caught out.

**Can a timestamp be negative?** Yes. Negative timestamps count backwards from the epoch, so they represent moments before 1 January 1970. For example, -86,400 is 31 December 1969 at midnight UTC. Many systems handle them correctly, but some tools and databases reject them, so test before relying on one.

### XML formatter
https://hopi.co.uk/xml-formatter/

Free XML formatter. Pretty print or minify XML instantly with clear messages when it will not parse. Runs entirely in your browser: nothing is uploaded.

**Is my XML uploaded anywhere?** No. Parsing and formatting happen entirely in your browser with the DOMParser built into it. Feeds, sitemaps, invoices and config files never leave your device, which makes the tool safe to use with data you would not paste into an unknown website.

**Why does my XML fail to parse?** The most common causes are a tag that is opened but never closed, tags closed in the wrong order, a bare ampersand that needs escaping as an entity, an attribute value missing its quotes, or more than one root element. The error message shown comes from your browser's parser and usually includes a line number.

**Does formatting change my data?** Element names, attributes, values and structure are all preserved. Whitespace between elements is normalised, which is what pretty printing means, and text inside elements is trimmed. If your document treats spaces and newlines inside mixed content as significant, keep a copy of the original.

**What is the difference between XML and HTML?** HTML is a specific vocabulary with forgiving parsing rules, while XML is a generic strict format for any vocabulary. XML requires every tag to be closed, attributes to be quoted and a single root element. Browsers repair broken HTML silently, but broken XML simply fails to parse.

**When should I minify XML?** Minifying strips the whitespace between elements, which shrinks payloads sent over the network or stored in bulk. It is worth doing for machine-to-machine traffic where no human reads the document. For anything a person needs to inspect or diff, the pretty printed form is worth the extra bytes.

## Crypto

### Bitcoin address validator
https://hopi.co.uk/bitcoin-address-validator/

Free Bitcoin address validator. Checks legacy, SegWit and Taproot checksums instantly in your browser. Nothing is uploaded and no balances are checked.

**Is my address sent anywhere when I check it?** No. The validation maths runs entirely in your browser with JavaScript. Nothing is transmitted, logged or stored, and the tool never looks anything up on the blockchain. Once the page has loaded it works with no connection at all.

**Does this tool show the balance of an address?** No. It checks structure and checksum only, which proves the address is well formed and free of typing errors. It does not query the blockchain, so it cannot tell you whether an address holds funds or has ever been used.

**What do the different address types mean?** Addresses starting with 1 are legacy P2PKH, a leading 3 means P2SH (often multisig or wrapped SegWit), bc1q is native SegWit (P2WPKH or P2WSH) and bc1p is Taproot. All are spendable; the newer formats generally mean lower transaction fees.

**Can a valid address still be the wrong address?** Yes. A passing checksum only proves the characters have not been mistyped. Malware that swaps addresses in your clipboard produces a different but perfectly valid address, so always compare the first and last few characters against the source before sending anything.

**Should I ever type my seed phrase into a website to check it?** Never. No legitimate website, wallet support team or airdrop needs your seed phrase or private key, and anyone who asks for one is trying to steal your funds. This tool accepts public addresses only, which are safe to share.

### Crypto DCA calculator
https://hopi.co.uk/dca-calculator/

Free crypto DCA calculator. Paste your buys as amount and price per line to see total invested, coins acquired, average cost and unrealised profit or loss.

**What format do the rows need?** One buy per line: the amount you spent, then the price you paid, separated by a comma, for example 100, 25000. Use plain numbers without pound signs or thousands separators. Any line that cannot be read is flagged with its line number so you can fix it, and the readable lines still calculate.

**Why is my average cost below the average of my buy prices?** Because a fixed amount of money buys more coins when the price is low and fewer when it is high. Your average cost is total money divided by total coins, which naturally leans towards the cheaper purchases. Averaging the prices themselves ignores how many coins each buy actually got you.

**Does pound cost averaging guarantee a profit?** No. It smooths out your entry price so no single badly timed buy dominates, but if the market falls and stays down, a drip-fed position loses money just like a lump sum. It manages timing risk, not market risk.

**Can I use this for shares or funds too?** Yes. The maths is identical for anything bought repeatedly at varying prices: units acquired equals money divided by price, and average cost equals total money divided by total units. Only the crypto framing is specific.

**Is my trading history uploaded anywhere?** No. Parsing and calculation all happen in your browser and nothing is stored or sent. As always, never enter a seed phrase or private key into any website, including this one. This tool only ever needs amounts and prices.

### Crypto profit calculator
https://hopi.co.uk/crypto-profit-calculator/

Free crypto profit calculator. Enter buy price, sell price, quantity and exchange fees to see profit or loss, return percentage and breakeven price.

**Why is the breakeven price higher than my buy price?** Because fees are usually charged twice, once when you buy and once when you sell. To walk away with the money you put in, the sale has to cover the original cost plus both fees. With a 0.5% fee per side, a coin bought at £20,000 must reach about £20,201 before you are back to zero.

**What fee percentage should I enter?** Use your exchange's trading fee for the market you traded, shown on its fees page or on each trade confirmation. Typical exchange fees run from about 0.1% to 1% per trade. If you were charged a flat amount instead, divide it by the trade value to turn it into a percentage.

**Does this work for any coin or token?** Yes. The calculator never looks up prices and has no list of tickers, so it works for any cryptocurrency, or any fraction of one. Enter the prices you actually paid and received in pounds, along with the quantity you traded.

**Do I owe tax on crypto profits in the UK?** Possibly. Selling crypto at a gain can trigger Capital Gains Tax once your total gains pass the annual exempt amount, and HMRC expects records of every disposal. This calculator ignores tax entirely, so check the cryptoassets guidance on gov.uk or ask an accountant.

**Is anything I type sent anywhere?** No. Everything is calculated in your browser and nothing is uploaded or stored. Even so, never enter a seed phrase or private key into any website, including this one. A profit calculator only ever needs prices and quantities.

### ETH unit converter
https://hopi.co.uk/eth-unit-converter/

Free ETH unit converter. Switch between wei, gwei and ETH instantly with exact 18-decimal maths and no floating point errors. Handy for reading gas fees.

**How many wei are in one ETH?** One ETH is 1,000,000,000,000,000,000 wei, which is 10 to the power of 18. One ETH is also 1,000,000,000 gwei, and one gwei is 1,000,000,000 wei. Wei is the smallest unit the Ethereum network records.

**What is a gwei?** Gwei is short for gigawei, one billion wei, which makes it one billionth of an ETH. It is the unit gas prices are quoted in, because typical gas prices come out as tidy numbers like 20 or 30 gwei rather than unreadable strings of zeros in either wei or ETH.

**How do I work out a gas fee in ETH?** Multiply the gas used by the gas price in gwei, then convert. A simple ETH transfer uses 21,000 gas, so at 30 gwei that is 21,000 × 30 = 630,000 gwei, which is 0.00063 ETH. Multiply that by your ETH price to see the fee in pounds.

**Why does the converter use BigInt instead of normal numbers?** Ordinary JavaScript numbers are floating point and only safe to about 15 or 16 digits, but one ETH is already a 19-digit number of wei. This tool parses your input as text, converts it to a BigInt number of wei, and moves the decimal point by shifting digits, so every result is exact.

**Is it safe to type amounts into this page?** The tool only ever needs plain numbers and runs entirely in your browser; nothing you type is sent anywhere and no prices are fetched. Never enter your seed phrase or private keys into any website, including this one. No legitimate converter needs them.

### Ethereum address checksum
https://hopi.co.uk/eth-address-checksum/

Free Ethereum address checksum tool. Validates EIP-55 capitalisation and produces the correctly checksummed form instantly in your browser. Nothing is uploaded.

**Is my address sent anywhere when I check it?** No. The keccak-256 hashing and the checksum comparison run entirely in your browser with JavaScript. Nothing is transmitted, logged or stored, and the tool works with no connection at all once the page has loaded.

**Why do Ethereum addresses mix capital and small letters?** The hex letters a to f mean the same thing in either case, so EIP-55 uses capitalisation as a free checksum. Each letter is capitalised or not according to the keccak-256 hash of the address, which lets wallets spot typos without changing the address itself.

**My address is all lower case. Is it wrong?** No. An all lower case address is perfectly valid and every wallet accepts it; it simply carries no checksum, so a typo cannot be detected. Copy the checksummed form this tool produces and you get exactly the same address with typo protection built in.

**Does a passing checksum mean the address is safe to send to?** No. It only proves the characters have not been mistyped. It says nothing about who controls the address, whether it is a contract, or whether it makes sense on the network you are using. Verify the address with its owner and consider a small test transfer first for large amounts.

**Should I ever type my seed phrase into a website to check it?** Never. No legitimate website, wallet support team or airdrop needs your seed phrase or private key, and anyone who asks for one is trying to steal your funds. This tool accepts public addresses only, which are safe to share.

### Market cap calculator
https://hopi.co.uk/market-cap-calculator/

Free market cap calculator. Multiply price by circulating supply to get market cap, or find the implied price at a target market cap. Instant and free.

**How is market cap calculated?** Market cap is the coin's current price multiplied by its circulating supply, the coins actually available today. A coin priced at 2.50 with 400 million circulating has a market cap of 1 billion. It is the standard way to compare the overall size of different coins.

**What is fully diluted valuation (FDV)?** FDV is the price multiplied by the maximum or total supply that will ever exist, rather than the coins circulating now. If FDV is far above the market cap, large amounts of the coin are still to be released, and that future supply can weigh on the price as it unlocks.

**What does the price at a target market cap mean?** It answers the question of what one coin would cost if the project were valued at some target figure. Divide the target market cap by the circulating supply. It is a useful sense check, but reaching another project's valuation is never guaranteed and the supply may grow along the way.

**Is a coin with a lower price cheaper?** Not by itself. Price per coin depends entirely on how many coins exist. A 0.10 coin with 100 billion in circulation is a far bigger project than a 50.00 coin with 10 million. Comparing market caps, not prices, is the honest comparison, which is exactly why this calculator exists.

**Does this calculator use live prices?** No. You enter every number yourself, including prices and supply figures, which you can take from any data site you trust. Nothing is fetched or sent anywhere, and it works in any currency. Never enter a seed phrase or private key into any website, including this one.

### Position size calculator
https://hopi.co.uk/position-size-calculator/

Free position size calculator for crypto. Enter account size, risk percentage, entry price and stop-loss to see how many units to buy and pounds at risk.

**What is the 1% risk rule?** It is the practice of risking no more than 1% of your account on any single trade, with 2% usually treated as the aggressive end. Risk here means the amount lost if the stop is hit, not the size of the position. Sized this way, even a run of ten straight losing trades only dents the account by around 10%.

**Why is the position value sometimes bigger than my account?** A very tight stop means each unit risks only a small amount, so the formula asks for a lot of units. If the total cost passes your account size, you could not open the position without leverage. Either widen the stop, accept a smaller position, or reduce the risk percentage.

**Does this work for short positions?** Yes. If the stop-loss you enter is above the entry price, the calculator treats the trade as a short and uses the same distance-based maths. The amount at risk is still the loss if the price moves against you to the stop.

**Does a stop-loss guarantee I only lose that amount?** No. In fast or thin markets the price can gap straight through a stop and fill at a worse level, called slippage, and crypto trades around the clock with no circuit breakers. Treat the amount at risk as a planning figure, not a hard ceiling.

**Is anything I enter sent anywhere?** No. All the maths runs in your browser and nothing is uploaded or stored. Never enter a seed phrase or private key into any website, including this one. A position size calculator only needs prices and percentages.

### Satoshi to BTC converter
https://hopi.co.uk/satoshi-converter/

Free satoshi to BTC converter. Turn sats into bitcoin, mBTC and bits (or BTC into sats) instantly, with exact whole-satoshi maths and no rounding errors.

**How many satoshis are in a bitcoin?** One bitcoin is exactly 100,000,000 satoshis. The satoshi is the smallest unit recorded on the Bitcoin network, named after its pseudonymous creator Satoshi Nakamoto. There is no smaller on-chain unit.

**What is 1 satoshi in BTC?** 1 satoshi is 0.00000001 BTC, or one hundred-millionth of a bitcoin. To convert any number of sats to BTC, divide by 100,000,000, which is the same as moving the decimal point eight places to the left.

**What are mBTC and bits?** A millibitcoin (mBTC) is a thousandth of a bitcoin, which is 100,000 sats. A bit, also called a microbitcoin, is a millionth of a bitcoin, which is 100 sats. They sit between the tiny satoshi and the large whole bitcoin, and this tool shows both alongside the main result.

**Why does the tool work in whole satoshis?** Computers store decimal fractions in binary floating point, so values like 0.1 cannot be held exactly and tiny errors creep into arithmetic. Satoshis are whole numbers, so this converter does all its maths on integers and only moves the decimal point as text. The results are exact at every digit.

**Does this tool show live bitcoin prices?** No. It converts between units only and never fetches prices or any other data. Everything runs in your browser and nothing you type is sent anywhere. Never enter a seed phrase or private key into any website, including this one; a unit converter only ever needs numbers.

### Staking rewards calculator
https://hopi.co.uk/staking-calculator/

Free staking rewards calculator. Enter your stake, the quoted rate as APR or APY, compounding frequency and term to see your final balance and rewards earned.

**What is the difference between APR and APY?** APR is the flat annual rate with no compounding included, while APY is what you actually earn in a year once rewards start earning rewards of their own. A 10% APR compounded daily works out at about 10.52% APY. Platforms often quote whichever looks better, so check which one you are being shown.

**Why does the compounding choice disappear when I pick APY?** Because APY already has compounding baked in. It tells you the total growth over a year whatever the schedule behind it, so adding a compounding frequency on top would count the same effect twice. The calculator simply grows your stake by the APY for each year of the term.

**Are staking rewards guaranteed?** No. Advertised rates change constantly with network conditions, rewards are usually paid in the coin itself so their pound value moves with the price, and some networks can slash staked funds for validator misbehaviour. Lock-up and unbonding periods can also stop you exiting when you want to.

**Are staking rewards taxed in the UK?** Usually, yes. HMRC generally treats staking rewards as miscellaneous income at their value when received, and selling the rewarded coins later can also trigger Capital Gains Tax. This calculator ignores tax, so check the cryptoassets guidance on gov.uk or speak to an accountant.

**Is anything I enter sent anywhere?** No. The calculation runs entirely in your browser and nothing is uploaded or stored. Never enter a seed phrase or private key into any website, including this one. Working out rewards needs a rate and an amount, nothing else.

## Files & data

### Add to calendar file generator
https://hopi.co.uk/ics-generator/

Free .ics file generator. Enter an event's title, times and location and download a calendar file that opens in Google, Apple and Outlook. Nothing is uploaded.

**What is a .ics file?** It is the standard calendar file format, defined by an internet standard called iCalendar (RFC 5545). Nearly every calendar app understands it, so one file works for Google Calendar, Apple Calendar, Outlook and most others. Opening the file offers to add the event to your calendar.

**Is anything uploaded when I create the file?** No. The file is assembled by JavaScript running on your own device and offered straight back as a download. Event details never travel over the internet, nothing is logged or stored, and closing the tab removes everything.

**How are time zones handled?** The times you enter are read in your device's local time zone and stored in the file as UTC, which every calendar app converts back to each viewer's local time. Enter 2pm UK time and a recipient in New York sees 9am, which is the same moment. Create the file on a device set to the event's time zone.

**What does the all-day option do?** It stores the event as a date rather than a time, so it appears in the all-day band at the top of the calendar and stays on the right date in every time zone. Behind the scenes the end date is stored as the day after the event finishes, because the format treats end dates as exclusive; the tool handles that for you.

**How do I share the event with other people?** Send them the .ics file by email or chat, or link to it from a website. Each person opens it and their own calendar app adds the event. For a large mailing list, attach the file to the invitation email so guests can add it with one tap.

### CSV to Excel converter
https://hopi.co.uk/csv-to-excel/

Free CSV to Excel converter. Paste CSV or drop a .csv and download a .xlsx that keeps leading zeros and dates intact. Runs in your browser, nothing uploaded.

**Is my CSV uploaded anywhere?** No. Whether you paste the text or drop a file, the conversion happens entirely in your browser and the .xlsx is assembled in memory on your device. Nothing is sent to a server, which makes this safe for customer exports and financial data, unlike converter sites that process your file remotely.

**Why not just open the CSV in Excel directly?** Double-clicking a CSV makes Excel guess what every value is. Leading zeros vanish from phone numbers and product codes, long numbers flip into scientific notation, and anything date-shaped is rewritten using your computer's locale. Converting first locks each value in place, so the spreadsheet shows exactly what the file said.

**How does the converter decide what is a number?** Only values that are unambiguous plain numbers, such as 42 or -3.75, become numeric cells. Anything with a leading zero, letters, spaces or more than 15 digits stays as text exactly as written, because those are the values Excel's own guessing tends to destroy.

**What happens to dates in my CSV?** They are kept as text in exactly the form the file used, so 01/02/2026 can never be silently swapped between 1 February and 2 January. If you need live date cells afterwards, convert the column deliberately in Excel with Text to Columns, where you can state the format explicitly.

**Does it handle quoted fields and commas inside values?** Yes. Standard CSV quoting is respected, so a field like "Smith, John" wrapped in double quotes comes through as one cell, and doubled quotes inside a quoted field become a single literal quote. Line breaks inside quoted fields are supported too.

### Dummy file generator
https://hopi.co.uk/dummy-file-generator/

Free dummy file generator. Create test files of an exact size in KB or MB, filled with random bytes, zeros or text, built in your browser and byte-verified.

**Is the file really exactly the size I asked for?** Yes, to the byte. The file is assembled from chunks whose lengths add up to precisely the requested size, and the actual size row is read back from the finished file rather than from the request, so what you see is what was built. A KB here is 1,024 bytes and a MB is 1,048,576 bytes.

**Which content type should I choose?** Random bytes for anything involving compression or transfer speed, because random data cannot be compressed and gives honest results. Zeros for the fastest possible generation when content is irrelevant. Repeating text when you want a file you can open and recognise in a text editor.

**Is the file safe?** Completely. It contains only inert bytes: random values, zeros or plain text. It is not executable and carries no metadata. It is generated on your device, so nothing is downloaded from the internet and nothing you create is uploaded anywhere.

**Why is there a 512 MB cap?** The file is built in your browser's memory before it can be saved, and both the chunks and the finished file exist together briefly. 512 MB is a size that modern desktop browsers handle comfortably; beyond that, tabs on lower-memory devices start to fail unpredictably. Above 100 MB the tool shows a memory warning for the same reason.

**What are dummy files actually used for?** Testing upload size limits on forms and APIs, checking backup and sync software, measuring real transfer speeds across networks or USB drives, filling storage to test low-space behaviour, and creating placeholder attachments. Anywhere you need a file of a known, exact size rather than a particular content.

### Dummy image generator
https://hopi.co.uk/dummy-image-generator/

Free dummy image generator. Draw placeholder images at any size with your colours and label, then download as PNG, JPG or WebP. Made in your browser.

**Which format should I download?** PNG is the safe default: it is lossless, so flat colour and text stay perfectly crisp, and every browser and design tool accepts it. JPG makes sense only if a system insists on it, and WebP gives the smallest files for web use. For a simple placeholder the differences are tiny either way.

**Why is the preview smaller than the size I typed?** The preview is capped at about 360 pixels so a 1920 wide placeholder does not take over the page. The image itself is always drawn at your exact pixel dimensions, and the download is the full size file. The dimensions row confirms exactly what you are getting.

**Can I make a transparent placeholder?** Not with this tool. The background is always filled with your chosen colour, because a placeholder's whole job is to occupy space visibly. If you need transparency, download the PNG and clear the background in an image editor, or simply pick a colour that matches its destination.

**What happens if I leave the label blank?** The label defaults to the image's own dimensions, such as 800x600, and updates automatically as you change the size. That convention makes layout problems obvious at a glance, because every misplaced image announces exactly how big it is. Type your own text to override it.

**Is anything uploaded to a server?** No. The image is drawn by the canvas built into your own browser, previewed locally and downloaded straight from memory, so it works offline once the page has loaded. Nothing you type or generate leaves your device.

### EXIF remover
https://hopi.co.uk/exif-remover/

Free EXIF remover. Strip location, device and timestamp metadata from photos in your browser and download a clean copy. Nothing is ever uploaded.

**Is my photo uploaded anywhere?** No. The photo is read and re-encoded by JavaScript running on your own device. It never travels over the internet, nothing is logged or stored, and closing the tab removes everything. That matters more than usual for a tool handling photos with location data in them.

**What does EXIF metadata actually contain?** Typically the GPS coordinates of where the photo was taken, the exact date and time, the camera or phone make and model, camera settings such as aperture and shutter speed, the editing software used, and sometimes a small embedded thumbnail. Most of it is written automatically without you ever seeing it.

**How does this tool remove it?** It redraws your photo pixel by pixel onto a blank canvas and saves the result as a fresh JPEG. Metadata lives alongside the pixels in the file, not inside them, so a file rebuilt from pixels alone contains no EXIF at all, including GPS. Nothing is selectively edited, so nothing can be missed.

**Does the image quality change?** Very slightly. The clean copy is re-encoded as a JPEG at quality 95, which is visually indistinguishable from the original for normal use. The embedded colour profile is also dropped, so photos taken in a wide gamut colour space may shift a little. Keep your original if exact fidelity matters.

**Do social networks not strip EXIF anyway?** The big platforms do remove metadata from photos they display publicly. But photos sent by email, some messaging apps, cloud storage links and your own website keep every byte of it. If a photo is leaving your hands, stripping the metadata yourself first is the only way to be sure.

### Excel to CSV converter
https://hopi.co.uk/excel-to-csv/

Free Excel to CSV converter. Drop a .xlsx or .xls file, pick a sheet and download it as a properly quoted CSV. Runs in your browser, nothing is uploaded.

**Is my spreadsheet uploaded anywhere?** No. The file is opened and converted entirely in your browser with JavaScript. It never leaves your device, nothing is stored, and once the page has loaded the converter works without an internet connection.

**What happens to my formulas?** CSV is plain text, so formulas cannot survive. Each formula cell is exported as its last calculated value, the same number you saw in Excel. The formula itself, along with all formatting, colours and column widths, is lost. Keep the original workbook if you need them back.

**My workbook has several sheets. What do I get?** A CSV file holds exactly one sheet, so the tool converts one sheet at a time. If the workbook has more than one sheet, buttons appear so you can switch between them, up to 8 sheets. Download each sheet you need as its own file.

**Why do my dates look different in the CSV?** Excel stores dates as serial numbers, such as 45658 for 1 January 2025, and only the display format makes them readable. This tool exports dates using the format saved in your file, so you get readable dates rather than serials, but the style follows whatever the spreadsheet specified.

**Will commas inside my data break the file?** No. Any value containing a comma, a quote or a line break is wrapped in double quotes, with inner quotes doubled, following the standard CSV rules. Software that parses CSV properly will read it back as one field.

### Excel to JSON converter
https://hopi.co.uk/excel-to-json/

Free Excel to JSON converter. Drop a .xlsx or .xls file, pick a sheet and get pretty-printed JSON to copy or download. Runs in your browser, nothing uploaded.

**Is my spreadsheet uploaded anywhere?** No. The file is opened and converted entirely in your browser with JavaScript. It never leaves your device, nothing is stored, and once the page has loaded the converter works with no internet connection at all.

**Why do dates come out as readable dates and not numbers?** Excel stores dates as serial numbers counting days from the end of 1899, so 1 January 2025 is really stored as 45658. This tool spots date cells and outputs them using the display format saved in your file, so you get a readable date instead of a bare serial number.

**What does the first row is headers option do?** When ticked, the values in the first row become the keys of each JSON object, so a Name column produces objects with a Name property. When unticked, every row including the first becomes a plain array of values, which suits sheets with no header row.

**My workbook has several sheets. Which one is converted?** The first sheet is converted automatically, and if the workbook contains more than one sheet a row of buttons appears so you can switch between them. Up to 8 sheets are shown. Each sheet is converted separately, so download each one you need.

**Why are numbers wrapped in quotes in the JSON?** Values are exported as the text Excel displays, so currency symbols, percentages and date formats survive the trip. That means numbers arrive as strings. If your code needs real numbers, convert the specific fields you trust after parsing, where you can handle blanks deliberately.

### Excel to XML converter
https://hopi.co.uk/excel-to-xml/

Free Excel to XML converter. Drop a .xlsx or .xls file, pick a sheet and get well-formed XML with one element per row. Runs in your browser, nothing uploaded.

**Is my spreadsheet uploaded anywhere?** No. The file is opened and converted entirely in your browser with JavaScript. It never leaves your device, nothing is stored, and once the page has loaded the converter works without an internet connection.

**What structure does the XML use?** A rows element wraps the whole sheet, each spreadsheet row becomes a row element, and each cell becomes a child element named after its column header. It is a simple, flat, predictable shape that XML tools and importers can consume without a schema.

**Why did some of my column names change?** XML element names are strict: no spaces, no brackets, no symbols, and they cannot start with a digit. Invalid characters are replaced with underscores and a leading underscore is added where needed, so Unit price becomes Unit_price and 2024 sales becomes _2024_sales. The values themselves are never altered.

**What happens to special characters in my data?** Values are escaped the standard XML way, so an ampersand becomes amp entity, and angle brackets become lt and gt entities. Any XML parser turns them back into the original characters when it reads the file, so nothing is lost.

**Why do dates come out readable instead of as numbers?** Excel stores dates as serial numbers, such as 45658 for 1 January 2025, and only the display format makes them readable. This tool detects date cells and writes them using the format saved in your file, so the XML contains dates you can read rather than bare serials.

### Favicon generator
https://hopi.co.uk/favicon-generator/

Free favicon generator. Turn any image into a real .ico file with 16, 32 and 48 pixel sizes, plus a 180px Apple touch icon, right in your browser.

**Is my image uploaded anywhere?** No. The .ico file is assembled byte by byte by JavaScript running on your own device. Your image never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**What sizes does the favicon contain?** The .ico file contains three versions of your image at 16, 32 and 48 pixels square, which covers browser tabs, bookmarks and desktop shortcuts. You also get a separate 180 pixel PNG for the Apple touch icon that iPhones and iPads use when a site is saved to the home screen.

**What happens if my image is not square?** Favicons are always square, so the tool crops your image to its largest centred square before resizing. If your logo sits off centre, crop the image yourself first so the important part survives. The preview shows exactly what will be used.

**Where do I put the files on my site?** Upload favicon.ico and apple-touch-icon.png to the root of your site, then paste the two link tags from the tool into the head of your pages. Most browsers will also find favicon.ico at the root automatically, but declaring it is the reliable route.

**What kind of image works best?** A simple, high contrast mark on a plain or transparent background. At 16 pixels there is no room for fine detail, thin lines or small text, so favicons work best when the shape reads clearly even as a thumbnail. Start from a square image of at least 180 pixels if you can.

### File hash checker
https://hopi.co.uk/file-hash-checker/

Free file hash checker. Get the SHA-256, SHA-1 or SHA-512 checksum of any file in your browser and compare it with the published hash. Nothing is uploaded.

**Is my file uploaded anywhere?** No. The file is read and hashed by JavaScript running on your own device, using the browser's built-in WebCrypto engine. Nothing travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**Which algorithm should I choose?** Use whichever one the download page published. If you have a choice, SHA-256 is the modern standard and the default here. SHA-512 is equally strong with a longer digest, while SHA-1 is offered only because many older sites still publish SHA-1 sums.

**What does a matching hash actually prove?** It proves the file on your device is byte for byte identical to the file the publisher hashed. That rules out corrupted downloads and tampering in transit. It does not prove the publisher is trustworthy, so always take the expected hash from the official site.

**Why is MD5 not included?** MD5 has been cryptographically broken for years, and attackers can create two different files with the same MD5 sum. Offering it would encourage a false sense of security. If a site only publishes an MD5 sum, treat it as a basic corruption check at best.

**Can it handle very large files?** Yes, within reason. The whole file is read into memory before hashing, so files of a few hundred megabytes are fine, but multi-gigabyte files may be slow or fail depending on your device's memory. There is no size limit imposed by the tool itself.

### HEIC to JPG converter
https://hopi.co.uk/heic-to-jpg/

Free HEIC to JPG converter. Drop iPhone photos, set the quality and download JPGs instantly. Runs entirely in your browser, nothing is uploaded.

**What is a HEIC file?** HEIC is the photo format iPhones have used by default since iOS 11 in 2017. It stores images with HEVC compression inside a HEIF container, which makes files roughly half the size of an equivalent JPG at similar quality. That is great for phone storage but bad for compatibility, because much of the software world still expects JPG.

**Why can't Windows open my HEIC photos?** Windows does not ship with a full HEVC decoder, partly because of patent licensing costs, so HEIC photos often show as blank icons or fail to open. Microsoft sells an extension in its store, but converting to JPG is free and gives you files that open everywhere, on any system, however old.

**Are my photos uploaded anywhere?** No. Most HEIC converter sites send your photos to their server, convert them there and send back the result. This one does not. The decoding and conversion run entirely inside your browser, so your photos never leave your device, nothing is stored, and closing the tab removes everything.

**Why do large batches take a while?** Because the conversion happens in your browser rather than on a server or in a native app, each photo takes a moment to decode and re-encode. A handful of photos convert in seconds, but a very large batch is slower than a dedicated desktop app would be. The progress note shows exactly where the batch is up to.

**Does converting lose quality?** A little, because JPG is a lossy format. At the default 90% quality the difference is invisible for almost all photos. Drag the slider higher for a closer match and a bigger file, or lower for smaller files. Expect the JPGs to be noticeably larger than the HEIC originals either way, since HEIC compresses more efficiently.

### Image compressor
https://hopi.co.uk/image-compressor/

Free image compressor. Shrink JPG file sizes with a quality slider and see the saving instantly. Runs entirely in your browser, nothing is uploaded.

**Is my image uploaded anywhere?** No. The compression runs as JavaScript on your own device using the browser's built-in JPEG encoder. Your photo never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**What quality setting should I use?** For photos on the web, 75 to 85 is the sweet spot: big savings with differences you will struggle to spot. Below about 60 you start to see blockiness and smudged detail. Above 90 the file grows quickly for gains most eyes cannot detect.

**Why is the compressed file sometimes bigger than the original?** If the original was already heavily compressed, re-encoding it at a high quality setting can produce more bytes than it started with. Graphics with flat colours and sharp edges can also grow, because they suit PNG better than JPEG. In either case, lower the slider or keep the original.

**Can I get the quality back afterwards?** No. JPEG compression is lossy, meaning the discarded detail is gone for good, and recompressing an already compressed image loses a little more each time. Always keep your original file and compress copies of it.

**Does it keep transparency?** No. The output is JPEG, which has no transparency, so any transparent areas are filled with white. If you need transparency to survive, keep the image as a PNG and use the image resizer to reduce its dimensions instead.

### Image cropper
https://hopi.co.uk/image-cropper/

Free image cropper. Drag and resize a crop box, lock it to 1:1, 16:9, 4:3 or 3:2, and download the cropped JPG or PNG. Nothing is uploaded to a server.

**Is my image uploaded anywhere?** No. The cropping is done by JavaScript running on your own device, using the browser's built-in canvas. The image never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**How do I move and resize the crop box?** Drag inside the box to move the whole selection, or drag any of the four corner handles to resize it. The dimmed area outside the box shows what will be cut away, and the crop size in pixels updates live as you drag.

**What does the aspect ratio lock do?** Choose 1:1, 16:9, 4:3 or 3:2 and the crop box keeps that exact shape however you resize it, which is handy for profile pictures, video thumbnails or prints. Free lets you drag any shape you like. Switching ratio recentres a fresh box at that shape.

**Does it keep my file format and quality?** PNG files are cropped and saved as PNG, keeping any transparency. Other formats, including JPG and WebP, are saved as a high quality JPG on a white background. Cropping only removes pixels from the edges, so the pixels you keep are untouched.

**What is the maximum image size?** There is no hard limit beyond your device's memory, since everything runs locally. Very large photos are scaled down for the on-screen preview so they stay easy to work with, but the crop is always applied at the image's full original resolution, so the download is full quality.

### Image resizer
https://hopi.co.uk/image-resizer/

Free image resizer. Set a new width and height with aspect ratio lock, resize any JPG or PNG in your browser and download it. Nothing is uploaded.

**Is my image uploaded anywhere?** No. The resizing is done by JavaScript running on your own device, using the browser's built-in canvas. The image never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**Will resizing reduce the quality?** Making an image smaller discards pixels, but browsers use high quality smoothing so the result usually looks crisp at its new size. Making an image larger cannot add detail that was never captured, so upscaled images look soft. Resize down whenever you can.

**What does the aspect ratio lock do?** It keeps width and height in the same proportion as the original, so nothing looks stretched or squashed. Change one dimension and the other updates automatically. Untick it only if you deliberately want to distort the image.

**Does the tool keep my file format?** PNG files are saved as PNG, which keeps any transparency. Other formats, including JPG and WebP, are saved as JPG on a white background. The download name includes the new dimensions so you can tell versions apart.

**What size should images be for the web?** For a full width photo on a modern site, 1600 to 2000 pixels wide is usually plenty. Blog images are often about 1200 wide and thumbnails 400 or less. Anything bigger than the space it will occupy is wasted bytes, so resize to roughly the displayed size.

### Image to Base64 converter
https://hopi.co.uk/image-to-base64/

Free image to Base64 converter. Drop an image to get a data URI plus ready-made CSS and HTML snippets to copy. Runs in your browser, nothing is uploaded.

**What is a Base64 data URI?** It is the entire image written out as text, wrapped in a small header like data:image/png;base64 so browsers know what it is. Because it is plain text, it can be pasted directly into HTML, CSS, JSON or code, and the image displays without needing a separate file or an extra network request.

**How much bigger does Base64 make an image?** About a third bigger. Base64 encodes every 3 bytes of the file as 4 text characters, so the text is roughly the original size multiplied by 4 and divided by 3. A 48 KB logo becomes about 64 KB of text.

**When should I embed an image instead of linking to it?** Embed tiny images that ship with the page anyway: icons, small logos, decorative bits under a few KB, or anything inside a single-file HTML document that must work offline. It saves a network request and keeps everything in one file.

**When is a data URI a bad idea?** For anything big or reused. Embedded images cannot be cached separately, so they are re-downloaded with every page that includes them, and they bloat your HTML or CSS. A large photo as Base64 makes pages slow to load and painful to edit. Link to a normal file instead.

**Is my image uploaded anywhere?** No. The file is read and encoded entirely in your browser. It never leaves your device and nothing is stored.

### JPG to PDF converter
https://hopi.co.uk/jpg-to-pdf/

Free JPG to PDF converter. Turn one or more JPG, PNG or WebP images into a multi-page PDF and download it. Runs in your browser, nothing is uploaded.

**Is my image uploaded anywhere?** No. The PDF is written entirely by JavaScript running on your own device. Your images never travel over the internet, nothing is logged or stored, and closing the tab removes everything. That makes it safe for ID documents, contracts and private photos.

**Can I combine several images into one PDF?** Yes. Select as many images as you like in one go, or drag them all onto the drop zone together. Each image becomes one page and the pages follow the order of your selection. Selecting a new set of files starts a fresh PDF.

**What size will the PDF pages be?** Each page is sized to match its image exactly, using the standard conversion of 96 pixels to 72 PDF points. So a 1600 by 1200 pixel photo becomes a 1200 by 900 point page. Nothing is cropped, stretched or squeezed onto A4.

**Does converting reduce image quality?** Images are re-encoded as JPEG at 92% quality, which is visually identical to the original for photos. PNG and WebP images with transparency are placed on a white background, because neither JPEG nor a printed page has transparency.

**Why is the PDF about the same size as my images?** The PDF stores the JPEG data for each page directly, plus a small amount of structure around it, typically well under a kilobyte per page. So the file size is roughly the sum of the re-encoded images, and the tool shows you the exact output size before you download.

### JPG to PNG converter
https://hopi.co.uk/jpg-to-png/

Free JPG to PNG converter. Drop a JPG and download a lossless PNG copy in seconds, with file sizes shown. Runs entirely in your browser, nothing is uploaded.

**Will converting to PNG improve the quality of my JPG?** No. Detail that JPG compression discarded is gone for good, and no format change can bring it back. The PNG is an exact, lossless copy of the JPG as it is now, artefacts included. What PNG does guarantee is that no further quality is lost from this point on.

**Why is the PNG bigger than my JPG?** Because PNG stores every pixel losslessly while JPG threw detail away to stay small. Storing the same picture exactly simply takes more bytes, and for photos the PNG is often five to ten times larger. That is expected and not a sign anything went wrong.

**When is converting JPG to PNG worth it?** When an upload form or piece of software insists on PNG, and when you are about to edit an image repeatedly. Editing a PNG and re-saving costs nothing, whereas every re-save of a JPG loses a little more quality. Converting once to PNG before a long editing session stops that decay.

**Does the PNG get a transparent background?** No. JPG has no transparency, so there is none to carry over. The PNG will look identical to the JPG. If you need the background removed, that is an editing job rather than a conversion job.

**Is my image uploaded anywhere?** No. The conversion happens entirely in your browser using the canvas element. Your image never leaves your device and nothing is stored.

### JSON to Excel converter
https://hopi.co.uk/json-to-excel/

Free JSON to Excel converter. Paste a JSON array of objects or arrays and download a real .xlsx file instantly. Runs in your browser: nothing is uploaded.

**Is my JSON uploaded anywhere?** No. The spreadsheet is built entirely in your browser with JavaScript and downloaded straight from memory. API responses, exports and customer data never leave your device, which is the big difference from converter sites that upload your file to a server.

**What shape does the JSON need to be?** An array. Either an array of objects, where each object becomes a row and its keys become the column headers, or an array of arrays, where each inner array becomes a row exactly as given. Anything else, such as a single object or a mix of the two, shows a clear error instead of guessing.

**What happens to nested objects?** They are flattened one level using dot keys. A value like address with city inside it becomes a column called address.city. Anything nested deeper than one level, and any array value, is written into the cell as JSON text so nothing is lost.

**Do numbers stay numbers in Excel?** Yes. JSON has real types, so a number in your data becomes a proper numeric cell you can sum and sort, booleans become TRUE and FALSE, and strings stay text. Null and missing values become empty cells.

**Can it produce more than one sheet?** No, the output is a single worksheet called Sheet1 in a standard .xlsx workbook. If you need several sheets, convert each array separately and copy the sheets together in Excel.

### Merge PDF files
https://hopi.co.uk/merge-pdf/

Free PDF merger. Combine two or more PDF files into one, reorder them before merging, and download the result. Runs in your browser, nothing is uploaded.

**Are my PDFs uploaded anywhere?** No. The files are read and the merged PDF is built entirely by JavaScript running on your own device. Nothing travels over the internet, nothing is logged or stored, and closing the tab removes everything. That makes it safe for contracts, payslips, ID scans and anything else you would not hand to a stranger's server.

**How do I control the page order?** The merged PDF follows the list on screen from top to bottom. Use the up and down buttons next to each file to move it, and the remove button to drop it from the list. You can keep adding more PDFs before you merge, and each new file joins the end of the list.

**Why was one of my files rejected?** Almost always because it is password protected or because it is not really a PDF. Rejected files are reported by name and every readable file still merges normally. For a protected PDF, open it in its original app, remove the password, save a copy and add that instead.

**Is there a limit on how many files I can merge?** There is no fixed limit on files or pages. Because the work happens in your browser's memory, the practical ceiling is your device, and merging hundreds of pages is normally quick. Very large files on an older phone may take a few seconds longer.

**Does merging reduce the quality?** No. Pages are copied across as complete objects rather than being re-rendered, so text stays sharp and selectable, images keep their original compression and links within a page keep working. The merged file is roughly the sum of the sizes of its parts.

### PNG to JPG converter
https://hopi.co.uk/png-to-jpg/

Free PNG to JPG converter. Drop a PNG, choose the quality and compare before and after file sizes, then download. Runs in your browser, nothing is uploaded.

**Why is the JPG so much smaller than my PNG?** PNG is lossless, so it keeps every pixel exactly and pays for it in file size, especially for photos. JPG is lossy: it throws away detail your eye barely notices, which is why a photo can shrink by 80% or more with no obvious change. The before and after rows show you exactly what you saved.

**What happens to transparent areas?** JPG has no transparency, so any transparent parts of the PNG are filled with white before converting. If your image needs a transparent background, for example a logo going onto a coloured page, keep it as a PNG.

**What quality setting should I choose?** The default of 92% is visually identical to the original for almost everything. Between 80% and 95% is the useful range for most photos. Below about 75% you will start to see blockiness and smudging, particularly around text and sharp edges.

**When should I keep the PNG instead?** Keep PNG for screenshots, logos, diagrams, text and anything with sharp edges or flat colour, because JPG compression visibly smears those. Also keep PNG if you plan to edit the image again, since every JPG save loses a little more quality.

**Is my image uploaded anywhere?** No. The conversion happens entirely in your browser using the canvas element. The image never leaves your device and nothing is stored.

### Photo metadata (EXIF) viewer
https://hopi.co.uk/exif-viewer/

Free EXIF viewer. Read the hidden metadata in a photo, including camera, settings, date and GPS location, entirely in your browser. Nothing is ever uploaded.

**What is EXIF metadata?** EXIF stands for Exchangeable Image File Format. It is a block of information that cameras and phones write into a photo alongside the picture itself. It can record the make and model of the device, the exposure settings, the date and time, and often the exact GPS location where the shot was taken.

**Is my photo uploaded anywhere?** No. The photo is read by JavaScript running on your own device and the metadata is decoded in the browser. Nothing is sent to a server, nothing is logged, and closing the tab clears everything. That matters here because the data being read can include where you were standing.

**Why does my photo show no metadata?** Several reasons are normal and harmless. Many social networks and messaging apps strip EXIF when you share a photo, screenshots rarely carry it, and PNG files usually have none. A photo with no metadata is a good thing for privacy, it simply has nothing to reveal.

**Why is there no location on my photo?** GPS is only written when location services were switched on for the camera at the time, and many people leave it off. Editing, resizing or exporting a photo can also drop it. If no GPS tags are present, the tool cannot invent them, so the location section is left out.

**How do I remove this metadata before sharing?** Use the EXIF remover, the companion tool linked below. It redraws the photo onto a blank canvas and saves a fresh copy that contains no EXIF at all, including GPS, so you can share the picture without giving away where or when it was taken.

### Rotate & flip image
https://hopi.co.uk/rotate-image/

Free image rotator. Turn any photo 90 degrees clockwise or anticlockwise, flip it horizontally or vertically, then download. Nothing is uploaded anywhere.

**Is my photo uploaded anywhere?** No. The rotation is done by JavaScript on your own device using the browser's canvas. The image never travels over the internet, nothing is logged or stored, and closing the tab removes everything.

**Why do my phone photos come out sideways?** Phones often save the photo exactly as the sensor captured it and record the intended orientation as a hidden note in the file. Software that ignores that note shows the photo sideways. Rotating and re-saving here bakes the correct orientation into the pixels themselves, so it displays upright everywhere.

**Can I combine rotations and flips?** Yes. Every button applies to whatever is currently on screen, so you can rotate twice for 180 degrees, or rotate once and then mirror. The orientation row describes the combined result, and Reset takes you back to the original at any point.

**Does rotating lose quality?** PNG files are re-saved as PNG, which is lossless, so nothing is lost. JPG and other formats are re-encoded as a high quality JPG, which in theory discards a tiny amount of detail, though in practice the difference is invisible for photos.

**What happens to the image dimensions?** A 90 degree turn swaps width and height, so a 4000 by 3000 photo becomes 3000 by 4000. Flips and 180 degree turns keep the dimensions as they are. The dimensions row always shows the size the download will have.

### SVG to PNG converter
https://hopi.co.uk/svg-to-png/

Free SVG to PNG converter. Export any SVG file as a crisp transparent PNG at 1x, 2x or 4x scale, right in your browser. Nothing is ever uploaded.

**Is my SVG uploaded anywhere?** No. The file is read and rendered by JavaScript in your own browser, and the PNG is generated on your device. Nothing is transmitted, logged or stored, and closing the tab removes everything.

**Why does my SVG come out blank or fail to convert?** The most common cause is external references: SVGs that link to separate image files, remote fonts or stylesheets cannot fetch those resources when rendered this way, so the linked parts are missing or the export is blocked. Embed images as data URIs and convert text to paths in your design tool, then try again.

**What size will the PNG be?** The SVG's own width and height, multiplied by the scale you pick. If the file declares no size, the viewBox dimensions are used instead, and failing that a default of 512 pixels. So a 24 by 24 icon at 4x becomes a 96 by 96 PNG.

**Why would I export at 2x or 4x?** High density screens pack more physical pixels into the same space, so a PNG exported at 1x can look soft on them. Exporting at 2x or 4x keeps icons and logos crisp on retina class displays, at the cost of a larger file.

**Does the PNG keep transparency?** Yes. The canvas starts fully transparent and the PNG format preserves it, so anywhere your SVG has no fill stays see-through. That makes the output ready to drop onto any background colour.

### Signature generator
https://hopi.co.uk/signature-generator/

Free signature generator. Draw a signature with your mouse, finger or stylus in black or blue ink and download a transparent PNG. Nothing is uploaded anywhere.

**Is my signature uploaded anywhere?** No. The drawing lives entirely on an invisible canvas in your browser and the PNG is assembled on your own device. Nothing is sent to a server, nothing is logged or stored, and closing the tab removes everything.

**Why is the background transparent?** A transparent PNG drops cleanly onto any document, whatever the page colour, without a white box around the ink. Word, Google Docs, PDF editors and email signatures all support transparent PNGs, so the signature looks like it was written on the page.

**How do I get a smoother line?** Draw slowly and at a comfortable size; the tool smooths your strokes as you go, but a slower hand always gives a cleaner curve. A stylus or a finger on a touchscreen usually beats a mouse. If a stroke goes wrong, Undo removes just that stroke rather than starting again.

**How do I put the signature in a document?** Download the PNG, then insert it as a picture in Word or Google Docs, or use your PDF editor's add-image option. Resize it to sit on the signature line. Because the background is transparent, it will not cover any text or lines beneath it.

**Is a drawn signature legally valid?** In the UK and many other countries, simple electronic signatures, including a drawn image, are generally capable of being legally valid for most everyday agreements. A pasted image proves little about who placed it, though, and some documents need witnessing or a formal signing platform, so check what your specific document requires.

### Split PDF
https://hopi.co.uk/split-pdf/

Free PDF splitter. Extract a page range like 3-7 as a new PDF, or split every page into its own file inside a ZIP. Runs in your browser, nothing is uploaded.

**Is my PDF uploaded anywhere?** No. The file is read, split and packaged entirely by JavaScript running on your own device, and the download comes straight from your browser's memory. Nothing travels over the internet, nothing is stored and closing the tab removes everything. That makes it safe for contracts, statements and scans of ID.

**How do I write a page range?** Use a dash for a run of pages and commas for a list, so 3-7 gives you pages 3 to 7 and 1,3,9 gives you those three pages. You can mix the two, like 1,3-5,9. Pages come out in the order you type them, and anything outside the document's page count is flagged before you extract.

**What does split every page give me?** One single-page PDF per page of your document, delivered together in a ZIP file. The files are numbered in order, for example report-page-01.pdf up to report-page-24.pdf, so they sort correctly in any file manager and you can send or archive exactly the pages you need.

**Can I split a password protected PDF?** No. A password protected file cannot be read without its password, so the tool reports it by name instead of splitting it. Open the PDF in the app it came from, enter the password, save an unprotected copy and split that copy instead.

**Do the extracted pages lose quality?** No. Pages are copied across as complete objects rather than being re-rendered, so text stays sharp and selectable and images keep their original compression. Each page carries the resources it needs, so a single extracted page is sometimes a little larger than you might expect.

### WebP to JPG converter
https://hopi.co.uk/webp-to-jpg/

Free WebP to JPG converter. Drop a WebP image, set the quality and download a JPG instantly. Runs entirely in your browser, nothing is uploaded.

**What is a WebP file?** WebP is an image format Google released in 2010. It compresses photos more efficiently than JPG at similar quality, which is why so many websites serve it. When you right-click and save an image from the web you often get a .webp file, even if the page originally showed a JPG.

**Why would I convert WebP to JPG?** Compatibility. Plenty of older software, upload forms, email tools and office templates still expect JPG and refuse WebP. Converting gives you a file that opens everywhere, at the cost of a slightly larger size.

**Does converting lose quality?** A little, because JPG is a lossy format. At the default 92% quality the difference is invisible for most photos. Drag the slider higher for a closer match and a bigger file, or lower for a smaller file with more visible compression.

**What happens to transparent areas?** JPG has no transparency, so any transparent parts of the WebP are filled with white before the conversion. If you need the transparency kept, convert to PNG instead.

**Is my image uploaded anywhere?** No. The file is decoded and converted entirely inside your browser using the canvas element. It never leaves your device and nothing is stored.

### XML to Excel converter
https://hopi.co.uk/xml-to-excel/

Free XML to Excel converter. Paste XML with repeated records and download a .xlsx with one row per record. Runs entirely in your browser: nothing is uploaded.

**Is my XML uploaded anywhere?** No. Parsing, record detection and building the .xlsx all happen in your browser with JavaScript, and the download is assembled in memory on your device. Nothing is sent to a server, which is the key difference from converter sites that process files remotely.

**How does it decide what a record is?** It looks for the element name that repeats most often under a single parent and treats each occurrence as one row. In a document like a rows element containing many row elements, each row becomes a spreadsheet row, its child elements and attributes become the columns, and the detected element name is shown so you can check it picked the right one.

**What XML shapes does it not handle?** It expects flat, repeated records: many elements with the same name whose children hold single values. Documents with no repeated element at all are rejected with a clear message. Deeply nested structures still convert, but anything below one level inside a record is flattened to its combined text rather than split into extra columns.

**Do attributes become columns?** Yes. An attribute on a record element, such as an id, gets its own column alongside the child elements. If a child element repeats inside one record, the extra occurrences get numbered columns such as tag_2 and tag_3 so no value is dropped.

**Do numbers come out as real numbers in Excel?** Values that are unambiguous plain numbers, like 42 or -3.75, are written as numeric cells you can sum and sort. Everything else, including codes with leading zeros and date-like strings, is kept as text exactly as it appears in the XML so nothing is reinterpreted.

## News

### Fiscal drag: how frozen tax thresholds quietly raise your bill
https://hopi.co.uk/news/fiscal-drag-frozen-thresholds-2026/
Published 2026-08-16 by Thomas Richardson. Category: Money & UK.

Frozen income tax thresholds mean pay rises push more of your money into higher bands. Here is how fiscal drag works and what it does to your take-home pay.

### A-level results: the percentage-point trap in the headlines
https://hopi.co.uk/news/a-level-results-percentage-point-trap/
Published 2026-08-16 by Thomas Richardson. Category: Maths & percentages.

A-level top grades edged up to 28.5% in 2026. How to read that without falling for the percentage-point trap, plus year-on-year change and UCAS points.

### How many calories do you actually burn in a day?
https://hopi.co.uk/news/how-many-calories-do-you-burn-a-day/
Published 2026-08-15 by Thomas Richardson. Category: Health & fitness.

Your daily calorie burn is your BMR plus movement. Here is how TDEE works, why the 2,000 a day guide is only an average, and how to find your own number.

### Why Britain still weighs itself in stones
https://hopi.co.uk/news/why-britain-still-weighs-in-stones/
Published 2026-08-12 by Thomas Richardson. Category: Converters & units.

Britain went metric decades ago, but body weight is still spoken in stones and pounds. The story of the 14-pound stone, and why converting it trips people up.