Steps shown
Open the working behind any answer, with the formula and each stage laid out.
Calculators that show their work.
Free online calculators for finance, health, maths and science, with the steps shown so you can check every result.
- Finance & Business
- Health & Fitness
- Math
- Science & Engineering
- Conversions
- Dates & Time
- Home & Construction
- Everyday Calculators
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- Steps shown. See how each answer is worked out and check it yourself.
- Works everywhere. Phone, tablet or desktop, nothing to install.
Instant and free
No sign-up and no limits. Type a value and the result is there immediately.
Works on any device
Designed for thumbs as much as keyboards, on phone, tablet or desktop.
Private by design
The numbers you enter are worked out in your browser, not saved to an account.
Browse by subject
The library is organised into 8 subjects, with 95 calculators live and more added every week.
Finance & Business
Margins, loans, salary, tax, rent and the everyday maths of running money.
Opening soonHealth & Fitness
Body measurements, calories and daily energy needs, with the formula named.
Opening soonMath
Algebra, geometry, ratios, statistics and more.
21 calculatorsScience & Engineering
Physics, electricity, chemistry, heat and fluids.
72 calculatorsConversions
Length, mass, volume and temperature, converted properly.
Opening soonDates & Time
Days between dates, time from now, ages and countdowns.
Opening soonHome & Construction
Concrete, paint, flooring, roofing and materials estimates.
2 calculatorsEveryday Calculators
Small jobs that come up all the time, from hobbies to household tasks.
Opening soonSee the numbers move
Drag the sliders to watch a balance grow with compound interest. This is a worked example, not financial advice.
Interest is added once a year and nothing is withdrawn. Real accounts differ, so use the calculators for your own figures.
Balance after years
Interest earned
Amount you started withInterest earned
| Year | Balance | Interest so far |
|---|
Formulas and conversions at a glance
The everyday maths behind our calculators, in one place.
Common formulas
| Name | Formula | Used for |
|---|---|---|
| Percentage | part ÷ whole × 100 | Shares, discounts, change |
| Simple interest | I = P × r × t | Loans and savings |
| BMI | kg ÷ m² | Weight for height |
| Circle area | π × r² | Round surfaces |
| Speed | distance ÷ time | Travel and motion |
| Pythagoras | a² + b² = c² | Right triangles |
| Profit margin | (revenue − cost) ÷ revenue × 100 | Pricing and business |
Handy conversions
| From | To |
|---|---|
| 1 inch | 2.54 cm |
| 1 mile | 1.609 km |
| 1 kilogram | 2.205 lb |
| 1 litre | 0.264 US gal |
| 1 acre | 4,047 m² |
| 0 °C | 32 °F |
| 1 hour | 3,600 seconds |
From question to answer in three steps
Here is what using any calculator looks like, shown with 15% of 200.
1
Enter your values
Fill in the fields. Units and hints are right there.
Percentage15
Of this number200
2
Get the answer
The result updates instantly, large and easy to read.
Result30
3
Check the working
Open the steps to see exactly how it was reached.
- 15 ÷ 100 = 0.15
- 0.15 × 200 = 30
- So 15% of 200 is 30
Enter values. Get the answer. See the steps.
A calculator is only useful if you can trust it. Ours are built to be checked, not just believed.
- Working shown
- Open the step-by-step view to see each stage of the calculation and the formula behind it.
- Free, with no sign-up
- Use any calculator as often as you like without creating an account.
- Works on any device
- Layouts adapt from phones to wide desktop screens, and the tools run in your browser.
- Units that make sense
- Switch between metric and imperial units without redoing the sum.
Questions people ask
Are the calculators free to use?
Yes. Every calculator on this site is free, works in your browser and needs no account or sign-up.
Can I rely on the results for medical or financial decisions?
Results are for general information and learning. They are not medical, financial or professional advice, so check important decisions with a qualified person. Our disclaimer explains this in full.
How are the results calculated?
Each calculator can show the working step by step, so you can see how an answer was reached and check it yourself.
Is my data stored anywhere?
Values you type into a calculator are processed in your browser. See our Privacy Policy for how the site itself handles data.
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