Fuel Economy (MPG) Calculator
Work out your car’s real fuel economy in miles per gallon (UK) and litres per 100 km from miles driven and litres used, plus cost per mile.
Enter your values and press Calculate.
How to use the Fuel Economy (MPG) calculator
For accuracy, fill the tank to the top, reset the trip meter, drive normally, then fill up again and enter the miles and the litres it took. Car trip computers are often a little optimistic.
Formula
UK mpg = miles ÷ (litres ÷ 4.546). A UK (imperial) gallon is 4.546 litres; a US gallon is 3.785 litres, so US mpg figures look about 17% lower.
Frequently asked questions
How do I work out mpg from litres?
Divide the litres by 4.546 to get gallons, then divide the miles by that. 400 miles on 32 litres is 56.8 mpg.
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