One converter, eight kinds of unit
This tool turns a number in one unit into the same amount in another — across length, weight, temperature, volume, area, speed, time and digital storage. Type a value on either side and the other updates instantly, so it works whether you are going from metric to imperial or back again. The table below the boxes shows your value in every unit in that category at once, which is handy when you are not sure which one you actually need.
How unit conversion works
Almost every conversion is a single multiplication. Each unit has a fixed size relative to one base unit — for length that base is the metre, for weight the gram, for volume the litre. To convert, you scale to the base and back out to the target: value × (size of your unit) ÷ (size of the target unit). Because the factors are exact and defined internationally, the answers are exact too — an inch is defined as 2.54 cm, a pound as 453.59237 g, a US gallon as 3.785411784 litres.
Metric and imperial
Most of the world measures in metric (metres, grams, litres, Celsius), which is built in tens so the units relate by moving a decimal point. The imperial and US customary systems (inches, feet, miles, pounds, ounces, gallons, Fahrenheit) grew up separately, so their steps are irregular — 12 inches to a foot, 16 ounces to a pound, 8 pints to a gallon. That irregularity is exactly why a converter is so useful: there is no clean decimal shortcut between the two families.
Popular conversions at a glance
| Convert | Equals |
|---|---|
| 1 inch | 2.54 cm |
| 1 centimetre | 0.393701 in |
| 1 foot | 30.48 cm |
| 1 mile | 1.60934 km |
| 1 kilogram | 2.20462 lb |
| 1 pound | 453.592 g |
| 1 stone | 6.35029 kg |
| 0 °C | 32 °F |
| 100 °C | 212 °F |
| 1 US cup | 236.588 ml |
| 1 US gallon | 3.78541 l |
| 1 mph | 1.60934 km/h |
| 1 GB | 1000 MB |
Temperature is the odd one out
Temperature is the only category here that is not a plain multiplication. Celsius, Fahrenheit and Kelvin scales start at different zero points, so converting means a stretch and a shift: Celsius to Fahrenheit is °C × 9/5 + 32, and Celsius to Kelvin is simply °C + 273.15. The converter applies the right formula automatically — you just read the answer.
A note on US and Imperial volumes
Cups, pints and gallons are not the same size everywhere. A US gallon is about 3.785 litres while an Imperial (UK) gallon is about 4.546 litres — roughly 20% bigger — and US and UK pints and fluid ounces differ too. This tool uses US customary volumes for cup, pint, quart and fluid ounce, and lists the Imperial gallon and pint separately so you can pick the right one.
Private and free
Every conversion happens in your browser. Nothing you type is sent to a server, stored, or logged, and once the page has loaded it keeps working offline. No sign-up, no limits.
Common questions
- How do I convert cm to inches?
- Choose Length, set the left box to centimetres and the right to inches, and type a value. One centimetre is 0.393701 inches (because an inch is exactly 2.54 cm), so 10 cm is about 3.94 inches. Type in the inches box to go the other way.
- How do I convert kg to pounds?
- Pick Weight with kilograms and pounds selected. One kilogram is about 2.20462 lb, so 70 kg is roughly 154 lb. A rough shortcut: double the kilograms and add ten percent.
- How do I convert Celsius to Fahrenheit?
- Choose Temperature. Multiply Celsius by 9/5 and add 32 — so 20°C is 68°F and 37°C is about 98.6°F. The converter does this for you in both directions.
- Is it accurate?
- Yes — it uses the exact, internationally defined conversion factors and shows seven significant figures. For everyday use the results are exact; only very large or very small numbers are rounded for display.
- Is it free and private?
- Yes. It is free, needs no sign-up, and everything runs on your own device. Nothing you type is ever uploaded.