Gas Mileage Calculator

Miles driven and gallons used — your real fuel economy.

mi
gal
$
Fuel economy
30.00 mpg
Cost per mile
$0.117

For the most accurate reading, measure from a full tank to a full tank and record the trip odometer — partial fill-ups introduce error from how full the pump nozzle actually fills the tank.

A worked example

Driving 300 miles on 10 gallons works out to exactly 30 mpg.

Frequently asked questions

Why does my calculated mpg sometimes vary between fill-ups?

Pump auto-shutoff doesn't fill to exactly the same level every time, and driving conditions (city vs. highway, weather, load) change real fuel consumption — tracking several fill-ups and averaging gives a more reliable number than any single tank.

How is this different from the Fuel Cost Calculator?

This tool works backward from an actual fill-up to find your real-world mpg. The Fuel Cost Calculator works forward — using a known or assumed mpg to estimate the cost of a planned trip.