Unit Converter
Convert length, mass, temperature, volume, area, and speed between metric and imperial. Type a value and the result updates live, with a full breakdown in every other unit underneath.
All units
About this unit converter
A single converter for the measurements you reach for most: length (millimetres to miles), mass (milligrams to stone), temperature (Celsius, Fahrenheit, Kelvin), volume (millilitres to US gallons), area (square centimetres to acres), and speed (m/s to knots). Every conversion uses exact internationally-defined factors — for example, one inch is exactly 0.0254 metres and one pound is exactly 0.45359237 kilograms.
How to use it
- Pick a category from the tabs — Length, Mass, Temperature, Volume, Area, or Speed.
- Type your value and choose the From and To units; the answer updates as you type.
- Press the ⇄ button to swap the two units and reverse the conversion.
- The All units list shows your value expressed in every unit at once.
Common conversions
- 0 °C = 32 °F · 100 °C = 212 °F (water's freezing and boiling points)
- 1 mile = 1.609 km · 1 km = 0.621 miles
- 1 kg = 2.205 lb · 1 lb = 453.6 g
- 1 US gallon = 3.785 litres
Are these US or imperial gallons?
Volume uses US customary units (US gallon, quart, pint, cup, fluid ounce). A US gallon is 3.785 litres; the UK imperial gallon is larger at 4.546 litres.
Why does temperature work differently?
Temperature scales have different zero points, so they can't be converted with a single multiply. Each value is first converted to Celsius, then to the target scale using the standard formulas.
How precise are the results?
Conversions are computed with full double-precision factors and shown to a sensible number of significant figures. Very large or very small results switch to scientific notation.