How to use the unit converter
- Pick a category — length, weight, temperature, volume or speed.
- Type a number and choose the units to convert from and to.
- The answer updates instantly. Hit the swap button to flip the direction.
Metric and imperial units
Most of the world uses the metric system — metres, kilograms, litres and Celsius — which is built on powers of ten. The imperial system — feet, pounds, gallons and Fahrenheit — is still common in the United States and for some everyday measures in the UK. Converting between them is one of the most frequent everyday maths tasks, whether you’re following a recipe, reading a weather forecast, or buying something from abroad.
Common conversion factors
| Conversion | Factor |
|---|---|
| 1 inch | 2.54 cm |
| 1 foot | 0.3048 m |
| 1 mile | 1.6093 km |
| 1 pound | 0.4536 kg |
| 1 kilogram | 2.2046 lb |
| 1 gallon (US) | 3.785 L |
| 0°C | 32°F |
Frequently asked questions
Length (mm to miles), weight (mg to stone), temperature (Celsius, Fahrenheit, Kelvin), volume (millilitres to gallons) and speed (m/s, km/h, mph, knots).
Yes. We use the exact international definitions — for example one inch is exactly 2.54 cm and one pound is exactly 0.45359237 kg — and round only the displayed result.
Yes — see the popular conversions above for dedicated cm to inches, kg to lbs, °C to °F pages and more, each with a quick-reference table.