Free Calculators
Percentage, age, BMI, loan and everyday maths calculators. All 12 run in your browser, so nothing you enter is uploaded.
Percentage Calculator
Work out percentages, percentage change, and what one number is as a percentage of another.
Age Calculator
Exact age in years, months and days from a date of birth on any date, plus age difference, a baby’s corrected age and test-scoring age.
BMI Calculator
BMI for adults, children and teens: category, healthy weight range, waist-to-height ratio and CDC BMI-for-age percentiles, in metric or imperial units.
Loan Calculator
Calculate monthly repayments, total interest and the full amortisation schedule for a loan.
Percent, Decimal and Fraction Converter
Convert between percentages, decimals and fractions in any direction, with simplest fractions, mixed numbers and repeating decimals.
Scientific Notation Converter
Convert decimals to scientific, E and engineering notation and back, with significant-figure rounding and exact digits at any size.
Odds Converter
Convert fractional, decimal and American odds and implied probability into each other, with the return on a stake.
Steps to Miles Calculator
Convert steps to miles or kilometres, and distance back to steps, from your stride length or height.
W-2 to 1099 Rate Calculator
Convert a W-2 hourly rate into an equivalent 1099 contractor rate, with every assumption shown and editable.
Concrete Calculator
Work out cubic yards, cubic metres and premix bags for a slab, footing or round column, with a waste allowance.
Cubic Yards to Tons Calculator
Convert cubic yards to tons and tons to cubic yards for gravel, sand, topsoil, mulch, asphalt and concrete.
Square Footage Calculator
Find the square footage of rectangles, triangles, circles and L-shaped rooms, and add several areas together.
About these calculators
Calculators for everyday sums and for the jobs where a formula is easy to get slightly wrong: percentages and percentage change, exact age, BMI, loan repayments, fractions and scientific notation, odds, and some building and work estimates.
Every calculator shows how it gets its answer — the formula, the assumptions and the inputs it used — so you can check the result rather than take it on trust. Results update as you type and nothing you enter leaves your device.
Calculators — questions
Can I rely on these results for money or health decisions?
Use them as a careful first estimate. The loan, W-2 to 1099 and BMI calculators state their assumptions on the page; a lender, accountant or doctor works from details these tools do not have.
Why do my figures differ slightly from another calculator?
Usually rounding or a different assumption — monthly versus daily interest, or which density a material uses. The assumptions each calculator uses are listed under its result.
Do the calculators work offline?
Yes, once the page has loaded. The arithmetic runs in your browser and needs no server.