MPG Calculator
MPG = miles driven ÷ gallons used. Drive 320 miles and fill 12.4 gallons and you averaged 25.8 MPG. Fill the tank fully at both ends of the measurement for an accurate result.
Most drivers land within 10% of the EPA combined rating. Coming in well under usually points to short trips, cold weather, low tire pressure, or heavy highway speeds.
How to use the mpg calculator
Enter your own numbers in the fields above and the result updates instantly — there is no submit step, no account, and no data leaves your browser. Everything is computed client-side from the values you type, so you can try several scenarios back to back and compare the outcomes without reloading the page.
For the most realistic result, use figures that reflect how you actually drive rather than best-case numbers. Fuel prices vary by state and by season, annual mileage is usually higher than people estimate, and EPA combined MPG is a laboratory rating that most drivers fall roughly 10-15% short of in mixed real-world use — more in cold weather, heavy traffic, or at sustained highway speeds. Running the calculation twice, once with optimistic inputs and once with conservative ones, gives you a realistic range instead of a single misleading number.
Treat the output as a planning estimate, not a quote. It does not include insurance, registration, financing interest, depreciation, or unscheduled repairs, all of which can move total ownership cost more than fuel does over a five-year window.
Frequently asked questions
How does the mpg calculator work?
MPG = miles driven ÷ gallons used. Drive 320 miles and fill 12.4 gallons and you averaged 25.8 MPG. Fill the tank fully at both ends of the measurement for an accurate result.
Is it free?
Yes. The calculator runs entirely in your browser, needs no sign-up, and nothing you enter is stored or sent anywhere.
Where can I find my vehicle's specs?
Look it up on its AutoSpecData model page — every figure comes from official manufacturer and EPA data, broken out by year, engine and drivetrain.
Don't know your MPG?
Every vehicle on AutoSpecData lists its official EPA city, highway and combined ratings year by year. Search your vehicle or start from the fuel economy rankings.