MPG to L/100 km Converter
Convert fuel economy between US mpg, imperial mpg, L/100 km and km/L.
Fuel for a journey
| Distance | Litres | Miles | US gallons |
|---|---|---|---|
| 100 km | 7.84 L | 62 mi | 2.07 US gal |
| 250 km | 19.6 L | 155 mi | 5.18 US gal |
| 500 km | 39.2 L | 311 mi | 10.36 US gal |
| 1,000 km | 78.4 L | 621 mi | 20.71 US gal |
Two ways of measuring the same thing
mpg and km/L measure economy — distance per unit of fuel, so bigger is better. L/100 km measures consumption — fuel per unit of distance, so smaller is better. They are reciprocals of each other, which is why the conversion is a division rather than a multiplication:
L/100 km = 235.215 ÷ US mpg
US mpg = 235.215 ÷ L/100 km
That constant is just 100 × 3.785411784 ÷ 1.609344 —
litres per gallon over kilometres per mile.
US and imperial gallons are different
The imperial gallon is 4.546 litres against the US gallon's 3.785, about 20% larger. So the same car is roughly 20% more economical in British mpg than in American mpg without anything changing. A UK figure of 40 mpg is about 33 mpg in US terms.
Why the reciprocal matters
Improvements in mpg are misleading. Going from 15 to 20 mpg saves far more fuel over the same distance than going from 40 to 50 mpg, even though the second looks like the bigger jump. Consumption figures like L/100 km make that comparison honest, which is the main argument for using them.
Official figures come from standardised test cycles. Real-world consumption depends heavily on speed, load, terrain and climate control.