Fuel Consumption Converter

Fuel economy units come in two families: distance per volume (mpg, km/L — higher is better) and volume per distance (L/100km — lower is better), so converting between them is a reciprocal, not a scaling. With the US gallon of 3.785411784 L, L/100km = 235.215 ÷ mpg (US).

Mind the gallon: imperial mpg uses the 4.54609 L gallon, so the same car reads higher in UK mpg — L/100km = 282.481 ÷ mpg (imperial). A car doing 30 mpg (US) does 36 mpg (imperial) and burns 7.84 L/100km.

The formula

Via km/L: mpg (US) × 0.425144 = km/L; mpg (imp) × 0.354006 = km/L; L/100km = 100 ÷ km/L

Worked example

A car rated at 30 mpg (US) burns 7.84 litres per 100 km — the figure on European spec sheets.

The example is pre-loaded in the result panel — press Calculate with your own numbers to replace it.

Frequently asked questions

How do I convert mpg to L/100km?

Divide 235.215 by the US mpg figure: 235.215 ÷ 35 mpg ≈ 6.72 L/100km. For imperial mpg, divide 282.481 instead.

Why is UK mpg always higher than US mpg for the same car?

The imperial gallon is about 20% larger, so a car travels about 20% more miles on each imperial gallon. The fuel burned per kilometre is identical.

Is higher or lower L/100km better?

Lower. L/100km measures fuel consumed, so 6 L/100km beats 8 L/100km — the opposite of mpg, where higher is better.

Category: Unit Conversions calculators

Converted consumption	7.8405
Summary	30 mpg (US) = 7.840486 L/100km