Gas Mileage Calculator (MPG)
Work out your car's fuel economy and convert between units.
Fuel economy in any unit
Fill the tank, drive, then fill again and record the distance and the fuel added. Dividing gives your real fuel economy. The US uses miles per gallon, much of the world uses litres per 100 km, and the UK uses miles per imperial gallon.
Example
On the first tab (miles and gallons) with the starting values shown (Distance driven 360 miles; Fuel used 12 gallons), Fuel economy comes out as 30. Other results include in litres per 100 km: 7.84; in kilometres per litre: 12.75.
Fuel economy is a lower number when you use more fuel in litres per 100 km, but a higher number in miles per gallon, so the scales run in opposite directions. Average over several tanks for a reliable figure.
Frequently asked questions
Are US and UK gallons the same?
No. A UK (imperial) gallon is about 20% bigger, so the same car shows a higher mpg in UK gallons.
Is a lower L/100 km better?
Yes. It means less fuel per distance.
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