Popular fuel economy conversions
Fuel economy units
Fuel economy is either distance per volume (mpg, km/L), where higher is better, or volume per distance (L/100 km), where lower is better. Converting between the two families is an inversion, not a multiplication. US and UK mpg differ because their gallons differ.
| Unit | Symbol | Scale | Definition |
|---|---|---|---|
| Kilometer per liter | km/L | — | |
| Liter per 100 km | L/100 km | — | Liters of fuel used to drive 100 kilometers. Lower is better. |
| Mile per US gallon | mpg | — | Miles driven per US gallon, the fuel economy figure on US window stickers. |
| Mile per imperial gallon | mpg (UK) | — | Miles per imperial gallon, used in the UK. About 20% higher than the US figure for the same car. |
| Mile per liter | mi/L | — |
Calculate with fuel economy
The smart calculator does arithmetic across fuel economy units and picks a sensible unit for the answer. Try 1 m + 1 ft.
Questions and answers
Which fuel economy units can I convert?
All 5: kilometers per liter, liters per 100 km, miles per US gallon, miles per imperial gallon, miles per liter.
What is the SI unit of fuel economy?
Fuel economy is either distance per volume (mpg, km/L), where higher is better, or volume per distance (L/100 km), where lower is better. Converting between the two families is an inversion, not a multiplication. US and UK mpg differ because their gallons differ.
Why does L/100 km go down when mpg goes up?
mpg measures distance per fuel (higher is better) while L/100 km measures fuel per distance (lower is better). One is the reciprocal of the other, so the conversion divides rather than multiplies.
How precise are the results?
Factors are the exact legal definitions where one exists (an inch is exactly 2.54 cm, a pound exactly 0.45359237 kg). Results show 10 significant digits by default; the precision menu offers 4 to 15.
Does the fuel economy converter work offline?
Yes. ConvertEasy is a progressive web app: after your first visit it keeps working with no connection, and you can install it to your home screen from the browser menu.