Percent shortcuts
| 1% | Divide by 100 |
|---|---|
| 10% | Move the decimal point one place left |
| 5% | Half of 10% |
| 15% | 10% plus 5% |
| 25% | Divide by 4 |
| 50% | Divide by 2 |
84 calculators that show their working
Numbers, explained.
Free calculators and converters for money, maths, dates, health and everyday life. Each one shows the formula, a worked example and the mistakes to avoid, and nothing you type leaves your browser.
- 84 tools
- 11 guides
- 7 categories
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Explore the tools
Percentage Calculator
Calculate a percentage of any number.
MathWhat Percent Is X of Y?
Find what percentage one number is of another.
MathPercentage Change
Calculate the percentage increase or decrease.
MathDiscount Calculator
Find the sale price after a discount.
MathVAT Calculator
Add VAT to a net price or extract VAT from a gross price.
FinanceTip Calculator
Calculate a tip and the total bill.
FinanceBill Splitter
Split a bill among people, including a tip.
FinanceAverage Calculator
Calculate the average of a list of numbers.
MathRatio Simplifier
Simplify a ratio of two numbers.
MathCompound Interest Calculator
Estimate investment growth with compound interest.
FinanceSimple Interest Calculator
Calculate interest without compounding.
FinanceLoan Payment Calculator
Estimate monthly repayments on a fixed-rate loan.
FinanceSavings Goal Calculator
Estimate monthly savings needed to reach a target.
FinanceROI Calculator
Calculate return on investment.
FinanceProfit Margin Calculator
Calculate profit and profit margin from revenue and costs.
FinanceMarkup Calculator
Calculate selling price from cost and markup.
FinanceCurrency Converter
Convert currencies using a rate you supply.
ConversionsBMI Calculator
Estimate body mass index from height and weight.
HealthDaily Calorie Estimate
Estimate daily energy needs using the Mifflin–St Jeor equation.
HealthWater Intake Estimator
Estimate a daily water baseline by body weight.
HealthAge Calculator
Calculate age from a date of birth.
DatesDate Difference
Find the number of days between two dates.
DatesAdd Days to a Date
Find a date a chosen number of days from a start date.
DatesLength Converter
Convert between common length units.
ConversionsWeight Converter
Convert mass and weight units.
ConversionsTemperature Converter
Convert Celsius, Fahrenheit and Kelvin.
ConversionsSpeed Converter
Convert speed between km/h, mph and m/s.
ConversionsVolume Converter
Convert litres, millilitres, gallons and cups.
ConversionsArea Converter
Convert square metres, hectares, acres and more.
ConversionsData Storage Converter
Convert bytes, kilobytes, megabytes and gigabytes.
ConversionsWord Counter
Count words, characters and sentences.
TextText Case Converter
Convert text to uppercase, lowercase or title case.
TextPassword Generator
Generate a random password in your browser.
UtilitiesUnix Timestamp Converter
Convert a Unix timestamp into a readable date.
DatesCharacter Limit Checker
Check text against a character limit.
TextBMI Calculator (Imperial)
Estimate BMI using pounds and inches.
HealthFuel Economy Converter
Convert between L/100 km, km/L and US mpg.
ConversionsBreak-even Calculator
Estimate units needed to cover fixed costs.
FinanceStatistics Calculator
Mean, median, mode, range and standard deviation.
MathGCD & LCM Calculator
Find the greatest common divisor and least common multiple.
MathUnit Price Comparison
Compare two products to find the better price per unit.
FinanceSales Tax Calculator
Add sales tax to a price or find the tax in a total.
FinanceHourly to Salary Calculator
Convert an hourly wage to weekly, monthly and yearly pay.
FinanceRunning Pace Calculator
Work out your pace per km and per mile.
HealthWorking Days Calculator
Count weekdays between two dates.
DatesDays Until a Date
Count the days to or since a date.
DatesRandom Number Generator
Pick random whole numbers in a range.
UtilitiesCAGR Calculator
Find the steady yearly growth rate between two values.
FinanceInflation Calculator
See how inflation changes prices and purchasing power.
FinanceElectricity Cost Calculator
Estimate what an appliance costs to run.
FinanceWeighted Grade Calculator
Weighted average of scores, and the final exam score you need.
MathRule of Three Calculator
Solve direct and inverse proportion problems.
MathFraction Simplifier
Simplify a fraction and see it as a decimal and a percent.
MathRoman Numeral Converter
Convert numbers to Roman numerals and back.
ConversionsNumber Base Converter
Convert between decimal, binary, octal and hexadecimal.
ConversionsNumber to Words
Write a number in English words.
TextDue Date Calculator
Estimate a due date from the last period.
DatesTime Duration Calculator
Hours between two times, minus a break.
DatesWeek Number Calculator
ISO week number, day of year and quarter for a date.
DatesMortgage Calculator
Estimate the monthly payment of a home loan.
FinanceLoan Affordability Calculator
Find the loan size a monthly payment can support.
FinanceSavings Growth Calculator
See savings grow with deposits and interest.
FinanceCredit Card Payoff Calculator
See how long a card balance takes to clear.
FinancePercentage Points Calculator
Difference between two percentages in points.
MathProbability Calculator
Chance of one outcome and of at least one success.
MathOdds to Probability Calculator
Turn odds like 3 to 1 into probabilities.
MathDice Roller
Roll up to 20 dice with any number of sides.
UtilitiesTime Card Calculator
Add up a run of shifts and count the pay.
DatesSleep Calculator
Plan bedtimes or wake-up times in sleep cycles.
HealthSquare Footage Calculator
Area of a rectangle in m², ft² and yd².
ConversionsPaint Quantity Calculator
How much paint a wall needs, coats included.
UtilitiesBody Fat Estimate (US Navy Method)
Tape-measure body fat percentage estimate.
HealthIdeal Weight Calculator
Weight ranges from classic formulas and BMI.
HealthFuel Cost Calculator
What a trip costs in fuel.
FinanceConcrete Calculator
Estimate concrete volume for a slab, with wastage.
UtilitiesTile Calculator
Work out how many tiles a floor or wall needs.
UtilitiesWallpaper Calculator
Estimate rolls of wallpaper for a room.
UtilitiesGravel Calculator
Convert area and depth into tonnes of gravel.
UtilitiesOvertime Pay Calculator
Add up regular pay and overtime in one go.
FinanceCalories Burned Calculator
Estimate calories burned for an activity.
HealthMacro Calculator
Split daily calories into protein, carbs and fat.
HealthMiles to Steps
Convert between distance and footsteps.
HealthTest Score Percentage
Turn points earned into a percentage score.
MathStacked Discounts
See the real total of several discounts in a row.
MathPocket cheat sheets
Numbers worth rememberingKitchen and everyday units
| 1 tsp | about 5 ml |
|---|---|
| 1 tbsp | about 15 ml |
| 1 US cup | about 237 ml |
| 1 oz | about 28 g |
| 1 lb | about 454 g |
| 180 °C | 356 °F |
Rules of thumb
| Rule of 72 | Years to double ≈ 72 ÷ rate |
|---|---|
| km to miles | Multiply by 0.62 |
| BMI | kg ÷ height in metres squared |
| Margin | Profit ÷ price, not ÷ cost |
| 1 GB | 1,000 MB (1 GiB = 1,024 MiB) |
| Remove VAT | Divide by 1 plus the rate |
Compound Interest Calculator · Profit Margin Calculator · VAT Calculator
Show your working
Every tool lists its formula and a worked example, so you can verify the answer yourself.
Understand the result
Each page explains how to read the result, when to use it and the mistakes to avoid.
Clear limits
Estimates are labelled as estimates. Read how we work on the methodology page.
Free online tools for everyday tasks
Use the tools above for everyday calculations, conversions, planning and text processing. Check your inputs before relying on results for financial, medical or other important decisions.
Financial estimates are illustrative and may exclude fees, taxes or other costs. Health-related estimates are not medical advice. See the disclaimer.