Fuel Economy Converters

US MPG and L/100km are inversely related — not just scaled versions of each other. The formula is L/100km = 235.215 ÷ mpg, so a car rated at 30 mpg works out to roughly 7.84 L/100km. Because the relationship is a reciprocal, doubling your mpg doesn't halve L/100km in a straight line: the curve is steep at low mpg values and flattens at high ones, which means the efficiency gain from going 15→20 mpg is larger in real terms than the gain from 40→45 mpg. Use the L/100km to MPG converter to see exactly where any value lands.

A separate wrinkle: US and UK gallons are not the same. One US gallon is about 3.785 L; one imperial gallon is about 4.546 L. That gap means a car posting 40 US mpg would show roughly 48 imperial mpg on the same fuel — a meaningful difference when comparing specs across markets. The 7 converters here handle both gallon standards, as well as km/L, which several Asian and Latin American markets use as their primary efficiency rating. For US/UK comparison, the MPG to MPG (UK) converter makes the adjustment in one step.

L/100km and km/L run in opposite directions to each other and to MPG: a lower L/100km means better economy, a higher km/L means better economy, and a higher MPG also means better economy. Keeping that in mind prevents misreading an improvement as a regression. The km/L to L/100km converter is useful when switching between those two frames. Pick any pair from the popular list below, or scroll down for the full set.