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.
Enter your figures
Your mpg, L/100km and, if you add a fuel price, cost per mile appear here as you type.
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.