MPG Calculator
Work out your car's real fuel economy from a fill-up, or convert between mpg and litres per 100km — plus your cost per mile if you know the fuel price.
Estimate only. MPG and cost-per-mile figures are estimates based on the values you enter — actual fuel economy varies with driving style, traffic, load, tyre pressure and weather.
How MPG is calculated
From a fill-up, we convert the litres you used into UK (imperial) gallons — dividing by 4.54609 — then divide the miles you drove by that figure to get miles per gallon. To convert between mpg and litres per 100km, we use the standard conversion L/100km = 282.481 ÷ mpg (and its inverse, mpg = 282.481 ÷ L/100km), which combines the imperial gallon, mile and kilometre definitions. If you enter a fuel price, we use the same UK-gallon method as our fuel cost calculator to show your cost per mile.