MPG Calculator
Calculate your vehicle's real fuel economy from the distance you drove and the fuel you used — shown in US MPG, UK MPG, km per litre and litres per 100 km.
E.g. the trip-meter reading between two fill-ups.
The amount it took to fill the tank back up.
The most reliable way to measure: fill the tank, reset the trip meter, drive normally, then fill up again and use the distance and the fuel added. MPG = miles ÷ gallons; L/100 km = litres ÷ km × 100 (lower is better). UK MPG uses the 4.546 L imperial gallon, US MPG the 3.785 L gallon.
30
MPG (US)
36.03
MPG (UK)
12.75
km/L
7.84
L/100 km
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How to use mpg calculator
- 1Fill the tank and reset your trip meter.
- 2Drive as normal, then fill up again and note the fuel added and distance driven.
- 3Enter the distance and fuel with their units.
- 4Read your economy in every common unit.
About this tool
Fuel economy is distance ÷ fuel: 420 miles on 14 US gallons is 30 MPG. The fill-up-to-fill-up method gives the most reliable real-world figure because it measures exactly the fuel the engine used over a known distance; a car's dashboard readout can be several percent optimistic.
The same economy is quoted in different units around the world. The US uses miles per US gallon; the UK uses miles per imperial gallon; Canada, Australia and Europe mostly use litres per 100 km, where lower is better. Useful shortcuts: L/100 km = 235.21 ÷ MPG (US), or 282.48 ÷ MPG (UK).
Economy varies a lot between trips — motorway driving, city traffic, cold weather, short journeys and heavy loads all change it — so averaging over several tanks gives a more representative number.
Frequently asked questions
Divide the miles driven since your last fill-up by the gallons it took to fill the tank again. 350 miles ÷ 10 gallons = 35 MPG.
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