Enter the distance you drove and the fuel it took to get your fuel economy in every common unit at once — miles per gallon, liters per 100 km, and km per liter — plus your cost per mile if you add the fuel price.
Track a full tank between fill-ups for the most accurate real-world figure.
How it works
MPG is distance divided by fuel: miles / gallons. The metric figures convert from there — L/100km = 235.215 / MPG, and km/L = MPG × 0.4251. Cost per mile is the fuel used times its price, divided by the distance.
FAQ
Why is L/100km inverted from MPG? MPG measures distance per fuel (higher is better), while L/100km measures fuel per distance (lower is better), so the two move in opposite directions.
For pure fuel spend on a trip, see the Fuel Cost calculator, and read How to Improve Fuel Economy.
Calculating fuel economy
Fuel economy is distance divided by fuel used, in whichever unit you prefer. MPG = miles ÷ gallons; for metric, L/100km = (litres ÷ km) × 100. Note MPG and L/100km move in opposite directions — higher MPG is better, lower L/100km is better — and they aren’t a simple linear conversion, which is why showing every unit at once is handy.
For the most accurate figure, fill the tank completely, reset the trip meter, drive normally, then refill and divide the miles by the gallons it took. A single tank can be skewed by terrain, weather, and driving style, so average several fill-ups for a true picture. Tracking it over time also flags problems early — a sudden drop can signal low tire pressure, a dragging brake, or a needed tune-up.