MPG to Litres per 100 km

How to use MPG to L/100km Converter

1. 1
   Check which gallon. American figures use the US gallon; British ones use the larger imperial gallon.
2. 2
   Enter the mpg. Both conversions are shown, so a mislabelled source is obvious.

About converting mpg to litres per 100 km

Fuel economy is measured two ways that run in opposite directions, and this is more than a notational difference. Miles per gallon expresses distance per unit of fuel, so bigger is better. Litres per 100 kilometres expresses fuel per unit of distance, so smaller is better. Converting between them is a reciprocal rather than a scaling, which is why no single multiplier exists and why the relationship is not linear. That non-linearity has a practical consequence people find counterintuitive. Improving a car from 15 to 20 mpg saves considerably more fuel over the same distance than improving another from 40 to 45, despite both being a five-mpg gain — because the first is a much larger proportional reduction in fuel consumed. Litres per 100 km makes this obvious, since it is linear in the quantity you actually buy, and it is a reasonable argument that the metric measure is the better instrument for deciding anything. The second complication is that there are two gallons. The imperial gallon used in the United Kingdom is 4.546 litres and the US gallon is 3.785, a difference of about twenty percent. British and American mpg figures are therefore not comparable, and a car quoted at 40 mpg in one country is not the same car quoted at 40 mpg in the other. Both conversions are shown here for that reason. It is also worth treating any official economy figure as an upper bound; laboratory test cycles run optimistic against real driving by ten to twenty percent.

Frequently asked questions