Find your fuel economy in MPG, or estimate what a trip will cost in fuel, using the same basic inputs.

How to Use the Mileage Calculator

Pick "Fuel Economy" to enter distance driven and fuel used and get MPG plus the L/100km equivalent, or switch to "Trip Cost" to enter distance, your vehicle's MPG, and the price per gallon and get the total cost of that trip.

Fuel economy and fuel cost are two different questions built into one tool, since knowing your mileage is usually step one toward estimating what a drive will actually cost.

Fuel Economy: MPG = distance ÷ fuel used
Trip Cost:    cost = (distance ÷ MPG) × price per gallon

The MPG figure here is US miles per gallon — a US gallon is smaller than a UK imperial gallon, so the same car reports a different MPG number depending on which gallon is doing the counting. L/100km sidesteps that and is shown alongside as a second reading.

MPG and L/100km Run in Opposite Directions

A bigger MPG number means better efficiency. A bigger L/100km number means worse efficiency — one measures distance per unit of fuel, the other measures fuel per unit of distance, and flipping between them isn't a straight-line conversion, it's a mathematical inversion:

L/100km = 235.215 ÷ MPG

Doubling fuel economy from 20 MPG to 40 MPG cuts fuel consumption from 11.76 L/100km to 5.88 L/100km — also exactly half, because inverting a doubled number halves it. That part lines up neatly.

What doesn't line up is comparing MPG points directly. Driving 300 miles at 10 MPG burns 30 gallons; at 20 MPG, it burns 15 — a 15-gallon saving for "+10 MPG." Make the same jump from 30 to 40 MPG and fuel drops from 10 gallons to 7.5 — a saving of just 2.5 gallons, for the identical "+10 MPG." Going from a low starting MPG buys far more real fuel savings than the same-sized jump higher up the scale.

Practically, that's why trading a 15 MPG truck for an 18 MPG one saves more fuel than trading a 45 MPG hybrid for a 50 MPG one, even though both swaps are "+3 MPG."