What does Unit Converter do?
Free unit converter for length, weight, temperature, volume, area, speed, time, data size, pressure, energy and fuel economy, using exact defined factors.
- Price
- Free
- Account
- Not required
- Processing
- Entirely in your browser; your data and files are not uploaded
- Works on
- Any modern browser on desktop, tablet or phone
- Category
- Financial Calculators
How to use the unit converter
- Choose a category such as length, volume or fuel economy.
- Pick the unit you are converting from and the unit you want.
- Type a value in either box. The other box updates as you type.
- Use Swap to reverse the units, and check the table below for the value in every unit of the category.
- Copy the result, download the table as CSV or share a link with your values.
Worked example
Common conversions
1 mile is exactly 1.609344 km. 100 °C is 212 °F. 1 imperial gallon is about 1.200949926 US gallons. 30 mpg (US) is 7.840486111 L/100 km, while 30 mpg (UK) is 9.416031211 L/100 km. A 1 TB drive holds 931.3225746 GiB, which is why it appears smaller in some operating systems.
How it works
Each linear unit is stored as an exact multiple of a base unit (for example 1 in = 0.0254 m, 1 lb = 0.45359237 kg, 1 US gal = 3.785411784 L, 1 imperial gal = 4.54609 L, 1 psi = 0.45359237 × 9.80665 ÷ 0.0254² Pa). A value is converted to the base unit and then to the target unit. Temperature uses offsets (°F = °C × 9/5 + 32, K = °C + 273.15), and L/100 km is the reciprocal of distance per volume (L/100 km = 100 ÷ km/L). Factors follow NIST Special Publication 811 and Handbook 44, the 1959 international yard and pound agreement, the UK Weights and Measures Act 1985, the SI Brochure and IEC 80000-13 for binary prefixes. Results are rounded to 10 significant figures for display to remove floating-point noise.
Assumptions
- The US cup is the customary cup of 8 US fluid ounces (236.5882365 mL); US nutrition labels use a 240 mL cup.
- Month and Gregorian year are long-run calendar averages (30.436875 and 365.2425 days); leap seconds are ignored.
- Calories are thermochemical (4.184 J); the Btu is the International Table Btu.
- Mercury pressure units use the conventional values in NIST SP 811.
Frequently asked questions
Why are there two kinds of gallons, pints and fluid ounces?
The US kept the older wine gallon of 231 cubic inches (3.785411784 L), while the UK defined the imperial gallon as 4.54609 L. Pints and fluid ounces differ too, so check which one a recipe or fuel figure uses.
What is the difference between GB and GiB?
A gigabyte (GB) is 1,000,000,000 bytes. A gibibyte (GiB) is 1,073,741,824 bytes (1,024³). Drive makers use GB; some operating systems show GiB values labelled as GB.
Why does L/100 km go down when mpg goes up?
L/100 km measures fuel used per distance, while mpg and km/L measure distance per fuel. They are reciprocals, so better economy means a lower L/100 km figure and a higher mpg figure.
Are the results exact?
The conversion factors are exact where the unit is defined exactly. Displayed results are rounded to 10 significant figures, which is far more precision than everyday use needs.
Limitations
- Does not cover US survey units, which were retired at the end of 2022, or historical and regional units.
- Cooking conversions between volume and weight (for example cups of flour to grams) depend on the ingredient and are not included.