How to Use the Gas Mileage Calculator

Distance driven and fuel used are the two required fields — switch the unit toggle to match however receipts and odometer actually report the numbers.

mpg = miles driven ÷ gallons used
L/100km = (liters used ÷ km driven) × 100

Worth noticing: mpg and L/100km run in opposite directions — a bigger mpg number means better economy, but a bigger L/100km number means worse economy, since one measures distance per fuel unit and the other measures fuel per distance unit. This Gas Mileage Calculator handles both conventions, plus km/L for a third way of expressing the metric side.