MPG Calculator
Work out MPG, L/100km, and fuel efficiency from trip data.
UK gallon = 4.546 litres
Miles per gallon (UK)
40
Imperial (UK) gallons
MPG (UK / imperial)
40
MPG (US)
33.3
Litres per 100km
7.1
Km per litre
14.15
A UK gallon is about 20% larger than a US gallon, so UK MPG figures look higher for the same real-world economy.
In-depth explanation
Enter distance driven and fuel used to calculate MPG and metric fuel economy (L/100km). Handy after a fill-up to track real-world efficiency. Everything runs locally in your browser — your inputs are not uploaded to produce the result.
Divide miles driven by gallons used. The calculator also converts to L/100km when you enter metric values. UK and US gallons differ in size. Use the unit options that match your region for accurate results.
It depends on the vehicle. Compare against your car’s typical figures and track changes over time. Tweak the inputs above to compare options, then copy or note the result you need.
Frequently asked questions
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