How to use the Unit Converter
- Pick a category, such as length or weight.
- Choose the units to convert from and to.
- Type a value — the result and a table of all units appear instantly.
Metric vs. imperial
The metric system (meters, grams, liters) is used by almost every country and by science worldwide. The US customary system (inches, pounds, gallons) is still used day-to-day in the United States, and the UK uses a mix — miles on road signs, stones for body weight and pints for beer.
Exact definitions
- 1 inch = 2.54 cm exactly (since 1959).
- 1 pound = 0.45359237 kg exactly.
- 1 US gallon = 3.785411784 liters; 1 UK gallon = 4.54609 liters.
- 1 mile = 1,609.344 meters.
Data units
Storage makers use decimal units (1 GB = 1,000,000,000 bytes) while many operating systems report binary units (1 GiB = 1,073,741,824 bytes). That is why a “1 TB” drive shows about 931 GB in Windows.
Convert a list of values
Use the units above for up to 500 numeric values, one per line. The batch table and CSV preserve each input alongside its converted value.
Popular conversions
- cm to inches
- inches to cm
- mm to inches
- inches to mm
- feet to meters
- meters to feet
- inches to feet
- km to miles
- miles to km
- yards to meters
- kg to lbs
- lbs to kg
- grams to ounces
- ounces to grams
- stone to kg
- stone to lbs
- Celsius to Fahrenheit
- Fahrenheit to Celsius
- Celsius to Kelvin
- ml to fl oz
- fl oz to ml
- liters to gallons
- gallons to liters
- cups to ml
- ml to cups
- sq ft to sq m
- sq m to sq ft
- acres to hectares
- hectares to acres
- km/h to mph
- mph to km/h
- MB to GB
- GB to MB
- psi to bar
- bar to psi
- kcal to kJ
- kJ to kcal
Frequently asked questions
How accurate are the conversions?
Conversions use exact international definitions and are shown to up to 10 significant digits.
Why are US and UK gallons different?
They come from different historical definitions; the UK (imperial) gallon is about 20% larger.