Calcwise / Maths and units / Unit converter
Unit converter
Pick a category, a value and the two units to convert between.
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About this tool: Unit converter
Converts between metric and imperial units, in the six groups people need most. The tool uses the exact international definitions, for example 1 inch = 2.54 cm, 1 pound = 0.45359237 kg and 1 mile = 1,609.344 m.
US and UK gallons are different sizes, so both are listed. Temperatures use their own formulas because the scales do not start at the same point.
Formula
Result = value × (factor of the first unit ÷ factor of the second), with every unit expressed in a base unit (metre, kilogram, litre, square metre or metre per second). Temperature: °F = °C × 9 ÷ 5 + 32, K = °C + 273.15.
Worked example
1 km = 0.621371 miles. 100 °F = (100 − 32) × 5 ÷ 9 = 37.78 °C.
Sources and data
- Formulas and data last reviewed
- Accuracy
- The result is plain maths: with valid input it is exact, and we only round to cents.
Frequently asked questions
How many centimetres are in an inch?
Exactly 2.54, by international agreement.
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.
Why does the temperature row show no factor?
Temperature scales are offset from each other, so there is no single multiplier to show.