How the converter works
Each type has a base unit, such as the metre for length and the kilogram for weight. Your amount is converted to the base unit and then to the unit you want. That means any pair of units works, and the same step gives you the full list of equivalents in the result.
Temperature is different because Celsius, Fahrenheit and Kelvin do not just differ by a scale factor: their zero points differ too. The calculator handles that, and it warns you if a temperature would be below absolute zero.
Worked examples
A 26.2-mile marathon is 26.2 × 1.609344 = 42.1648 km. A 150 lb person weighs 150 × 0.45359237 = 68.04 kg. A 2 litre bottle holds 2 ÷ 0.2365882365 = 8.45 US cups. A garden of 2 acres is 2 × 4046.8564 = 8,093.7 m², or 0.81 hectares. Driving at 60 mph is 96.56 km/h.
Tips for accurate conversions
Check which system a measure comes from before converting, especially for volumes. A recipe from the UK may use imperial pints and a US recipe may use US cups. If the source is unclear, the difference can matter.
For a mix of feet and inches such as 5 ft 10 in, use the feet and inches calculator, which adds and subtracts them, and for fuel costs on a trip try the fuel cost calculator.
Questions people ask
How do I convert between metric and imperial units?
Choose the type (for example length), then the unit you have and the unit you want. The calculator multiplies by the exact conversion factor: 1 inch is exactly 2.54 centimetres, 1 mile is exactly 1.609344 kilometres, and 1 pound is exactly 0.45359237 kilograms.
Are the conversions exact?
Most are exact by definition: since 1959 the inch, yard and pound are defined in metric units, and the US gallon is defined as 231 cubic inches (3.785411784 litres). Results are shown to up to six decimal places. Year length uses 365.25 days.
What is the difference between a US and a UK gallon?
A US gallon is 3.785 litres and a UK (imperial) gallon is 4.546 litres, about 20% bigger. Cups, pints and quarts also differ between the two systems, so this converter lists US measures and the UK gallon separately.
Why are there two kinds of megabyte?
Storage makers and network speeds use powers of 1000: 1 MB is 1,000,000 bytes. Some operating systems use powers of 1024 and call that a megabyte too. To avoid confusion, the IEC names the 1024 version a mebibyte (MiB), and we list both.
How do I convert Fahrenheit to Celsius?
Subtract 32 and multiply by 5/9. So 98.6°F is (98.6 − 32) × 5/9 = 37°C. To go back, multiply by 9/5 and add 32. Pick the Temperature type to do it here, or use the dedicated temperature calculator.