MPG Calculator Miles per Gallon MPG Calculator. Work out your Miles per Gallon – MPG from your Distancetravelledand Litres of Fuel used…Enter Mileage travelled and Fuel used since last fill-up: Distance travelled : miles Fuel used : litres Consumption: Miles per Imperial Gallon Miles per US Gallon Litres per 100km Kilometres per litre US Gallons are smaller than British Imperial Gallons (1 Imp Gal = 1.201 US Gal = 4.546 litres) Please note that this information is provided as aGUIDE ONLY we cannot be held responsible for any errors.