Start with the quantity
Convert length to length, mass to mass, and volume to volume. Do not confuse ounces by mass with fluid ounces: they share a name but measure different things. Temperature needs the right formula instead of a single multiplication factor.
Multiply or divide by a conversion factor
A conversion multiplies or divides a value by the factor between the two units. One inch is exactly 2.54 centimetres, so 12 inches equal 30.48 centimetres. One kilogram is about 2.205 pounds, so 3 kg is about 6.61 lb.
Volume examples
One U.S. liquid gallon is about 3.785 litres. One litre is about 0.264 U.S. gallons. These figures are rounded for everyday conversions; keep more digits when your calculation needs greater precision.
Use the temperature formula
To convert Fahrenheit to Celsius, subtract 32 and divide by 1.8. To convert Celsius to Fahrenheit, multiply by 1.8 and add 32. To convert Kelvin to Celsius, subtract 273.15. For example, 68 °F equals 20 °C.
Check U.S. customary and Imperial units
This converter includes U.S. gallons and cups. They are different from British Imperial units: an Imperial gallon is larger than a U.S. gallon. Check which system your recipe, label, manual, or supplier uses before converting.
Use the converter and check rounding
Choose length, mass, volume, or temperature, enter a value, then select the starting and target units. The converter works in your browser. Displayed results may be rounded; for a technical specification, keep enough decimal places and verify the required tolerance.