Fuel Economy Converter
Convert mpg (US and UK), km/L and L/100km in any direction.
All units
About this tool
Convert fuel economy between the four figures used around the world: miles per US gallon, miles per imperial (UK) gallon, kilometers per liter, and liters per 100 km. The last one runs in the opposite direction (lower is better), and the converter handles the inverse math exactly rather than with a lookup table.
Useful when comparing a US spec sheet against a European one, or making sense of a rental car's dashboard abroad. The two gallon sizes are the classic trap: the same car scores about 20% higher in UK mpg than US mpg because the imperial gallon is bigger. Handy anchor: 1 mpg US is 235.2 L/100km, and 23.5 L/100km is 10 mpg. Everything runs locally in your browser as you type.
Frequently asked questions
- Why does L/100km go down when mpg goes up?
- They measure opposite things: mpg counts distance per amount of fuel, L/100km counts fuel per distance. A more efficient car has a higher mpg and a lower L/100km; 30 mpg US is about 7.8 L/100km.
- Why are US and UK mpg different?
- The gallons differ. A UK (imperial) gallon is 4.546 liters against the US 3.785 liters, about 20% more, so the same car scores a higher mpg figure in the UK. 40 mpg UK is only about 33.3 mpg US.
- What has no mpg equivalent?
- 0 L/100km would mean driving without using fuel, which maps to infinite mpg; the converter shows a placeholder rather than a made-up number.