Gas Mileage Calculator
Calculate your vehicle's real MPG between fill-ups.
Quick answer
Fuel economy is distance driven divided by fuel used — miles per gallon (MPG) or litres per 100 km. Fill the tank, drive, refill, then divide the miles since the last fill by the gallons it took to top off.
Fuel economy
29.6 MPG
Liters per 100 km
8
Km per liter
12.6
Miles per liter
7.81
Measuring it honestly
Fill the tank, zero the trip odometer, drive normally, refill at the same pump orientation, and divide miles by gallons pumped. Averaging three tanks smooths out pump-shutoff variance. Dashboard MPG readouts typically flatter by 3–7%.
What moves MPG
Under-inflated tires, roof cargo, and speeds above 65 mph each shave several percent; aggressive acceleration is the biggest single factor in city driving. A sudden unexplained drop of 15%+ is worth a mechanic's look — think dragging brakes or a failing oxygen sensor.
Frequently asked questions
- How does the Gas Mileage Calculator work?
- Fuel economy is distance driven divided by fuel used — miles per gallon (MPG) or litres per 100 km. Fill the tank, drive, refill, then divide the miles since the last fill by the gallons it took to top off.
- Is the Gas Mileage Calculator free to use?
- Yes. The Gas Mileage Calculator is completely free, runs entirely in your browser, and requires no account or sign-up. Your inputs never leave your device.
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