How to use the fuel economy converter
- 1Type a fuel economy figure into any of the four boxes.
- 2Read the equivalent in the other units.
- 3Use L/100 km when comparing cars in Europe, Canada and Australia, and MPG in the US and UK.
Two ways of measuring
- MPG and km/L measure distance per amount of fuel. Higher is better.
- L/100 km measures fuel used over a fixed distance. Lower is better.
Because one is the inverse of the other, the conversion is not a simple multiplication: L/100 km = 235.21 ÷ US MPG.
US and UK gallons are different
A US gallon is 3.785 liters, but a UK (imperial) gallon is 4.546 liters. The same car therefore shows about 20% higher MPG in the UK. 30 US MPG equals about 36 UK MPG. Always check which gallon a figure uses.
Why L/100 km is easier to compare
Fuel used, not distance travelled, is what you pay for. Improving a car from 10 to 20 MPG saves far more fuel than going from 40 to 50 MPG, which is obvious in L/100 km (23.5 to 11.8, versus 5.9 to 4.7) but easy to miss in MPG.
Frequently asked questions
What is 30 mpg in L/100 km?
30 US MPG is about 7.84 L/100 km. 30 UK MPG is about 9.42 L/100 km.
Why is UK MPG higher than US MPG for the same car?
A UK gallon is larger (4.546 liters versus 3.785), so the car travels further per gallon.
What is good fuel economy?
For a modern petrol car, below about 6 L/100 km (above roughly 40 US MPG) is efficient, though it depends on vehicle size.
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