MotionShine01 / Length and weight
The 1959 agreement
The international yard is exactly 0.9144 m and the pound exactly 0.45359237 kg, so inches, feet, miles, ounces and stones follow exactly.
Free tool
Unit converter, exact, not rounded.
Convert between metric, US and imperial units in ten groups: length, weight, volume, temperature, area, speed, data size, time, pressure and energy. Type in either box and see every other unit in the group at the same time. The factors come from the official definitions, like the international inch of exactly 2.54 cm and the US gallon of 231 cubic inches, so results are exact, not rounded guesses.
In every unit
Conversions happen in your browser.
Where the numbers come from
Defined, not measured.
02 / Volume
US and UK differ
The US gallon is 231 cubic inches, 3.785411784 litres; the UK gallon is 4.54609 litres. Cups, pints and fluid ounces follow from each.
03 / Data
Kilobyte or kibibyte
A kilobyte is 1,000 bytes and a kibibyte 1,024. Drives are sold in gigabytes; some systems report gibibytes, which is why a drive looks smaller.
Questions
Good to know.
How many centimetres are in an inch?
Exactly 2.54. An inch was defined as 2.54 cm by international agreement in 1959.
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.
Why are US and UK pints different?
They come from different gallons: a US pint is about 473 mL, a UK pint about 568 mL. Pick the right one in Volume.
Why does my 1 TB drive show 931 GB?
The drive has 1,000,000,000,000 bytes; many systems count in gibibytes of 1,073,741,824 bytes, which gives about 931.
How exact are the results?
Factors are the official definitions; results show up to 12 significant figures.