Unit Converter — metric and imperial, side by side
Convert length, weight, area, volume, temperature and data size between metric and imperial units, with every unit in the category listed at once.
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About the Unit Converter
Most unit conversion is one multiplication, but the constant is rarely the one you remember. An inch is exactly 2.54 cm and a pound is exactly 0.45359237 kg — both defined, not approximated, since the international yard and pound agreement of 1959. This converter uses those exact factors rather than rounded ones, so a chain of conversions does not drift.
Temperature is the exception, because Celsius and Fahrenheit have different zero points as well as different step sizes. Converting between them needs an offset as well as a ratio: °F equals °C times 9/5 plus 32, and Kelvin equals °C plus 273.15. Volume has its own trap — the US gallon, quart, pint and fluid ounce are all smaller than the imperial versions still used in the UK, so a US gallon is 3.785 litres while an imperial gallon is 4.546. The volumes here are the US customary ones, which is what American recipes and product labels mean.
Rather than making you convert one pair at a time, the table underneath shows your value in every unit in the category simultaneously. Type a length once and read it in millimetres, metres, inches, feet and miles together. Everything runs in your browser, with no rounding until the moment the number is displayed.
How to use it
- Pick a category: length, weight, area, volume, temperature or data size.
- Choose the unit you are converting from and the unit you want.
- Type a number into either box — the conversion runs in both directions, so you can work backwards from the answer.
- Read the table below for the same value expressed in every other unit in that category.
- Use Swap to flip the two units, or Copy result to put the converted value on your clipboard.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54 cm. This is a definition rather than a measurement — the international inch was fixed at 2.54 cm in 1959 — so the conversion is exact in both directions: 1 cm is 0.3937 in.
How do I convert kg to pounds?
Multiply kilograms by 2.20462 to get pounds, or divide pounds by that number to get kilograms. The exact definition is the other way round: one pound is precisely 0.45359237 kg. So 70 kg is about 154.3 lb.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. So 20 °C is 68 °F and 100 °C is 212 °F. Going the other way, subtract 32 first and then multiply by 5/9. The two scales cross at −40, which is the same temperature in both.
Is a US gallon the same as an imperial gallon?
No. A US gallon is 3.785 litres and an imperial gallon, still used in the UK, is 4.546 litres — about 20% larger. The same applies to quarts, pints and fluid ounces. The volume units in this converter are US customary, which is what American recipes and packaging use.
Is a kilobyte 1000 or 1024 bytes?
It depends who is counting. This converter uses the binary convention, where 1 KB is 1024 bytes and 1 MB is 1,048,576 bytes, which is how operating systems report file sizes. Storage manufacturers use decimal units — 1 GB as 1,000,000,000 bytes — which is why a "1 TB" drive shows up as roughly 931 GB in your file manager.
Are the conversions done on a server?
No. Everything is calculated in your browser in JavaScript. Nothing you type is uploaded or logged.