Unit Converter
Convert length, weight, temperature, volume, area and speed units, with the formula used for each conversion.
1 km equals
0.621371 mi
Formula used
mi = km ÷ 1.609344
Results are rounded to 6 significant digits.
How to use this converter
Pick a tab (Length, Weight, Temperature, Volume, Area or Speed), type a value, and choose the units to convert from and to. The result updates as you type. Use the swap button to reverse the conversion, and check the formula shown under the result.
How the calculation works
Each unit has an exact size in a base unit (metre, kilogram, litre, square metre or metre per second). A value is converted with result = value × size of the from unit ÷ size of the to unit. The converter uses these exact definitions:
- 1 inch = 2.54 cm, and 1 mile = 1.609344 km
- 1 pound = 0.45359237 kg
- 1 US gallon = 3.785411784 L, and 1 UK gallon = 4.54609 L
Temperature uses formulas, not factors: °F = °C × 9/5 + 32, °C = (°F − 32) × 5/9 and K = °C + 273.15.
Scope and common mistakes
Results are rounded to 6 significant digits for display. Cooking measures such as cups and spoons are not included, because their sizes vary.
- Mixing up US and UK gallons or fluid ounces.
- Converting square units with a length factor: 1 m is 3.28 ft, but 1 m² is about 10.76 ft².
- Converting a temperature difference with the temperature formula: a change of 10 °C is a change of 18 °F, not 50 °F.
How many centimetres are in an inch?
Exactly 2.54. The inch is defined as 2.54 cm, so 12 inches (1 foot) is 30.48 cm.
How do I convert kilograms to pounds?
Divide the kilograms by 0.45359237, because 1 pound is defined as exactly 0.45359237 kg. For example, 10 kg is about 22.0462 lb.
How do I convert Celsius to Fahrenheit?
Multiply by 9/5 and add 32. So 100 °C is 212 °F, 0 °C is 32 °F, and −40 °C is also −40 °F, the one point where the two scales meet.
Why are there US and UK gallons?
They are different sizes. A US gallon is exactly 3.785411784 litres and a UK (imperial) gallon is exactly 4.54609 litres. Fluid ounces differ too, so pick the one your recipe or label uses.
Why does a result look rounded?
Results are shown to 6 significant digits so they stay readable. The conversion itself uses the exact defined factors, and the formula below the result shows the factor used.