How to calculate mpg
MPG = miles ÷ gallons L/100km = 235.215 ÷ MPG
Worked example. Fuel economy: 28.6 MPG.
Example inputs — Miles driven: 320 mi; Gallons used: 11.2 gal. Starting values are illustrative.
From George Guju, founder of Calculyn · Educational calculator guidance, not professional advice.
How it works
Miles per gallon is distance divided by fuel used. For metric, 235.21 ÷ MPG gives liters per 100 km.
Assumptions & limitations
- Real fuel economy varies with speed, load, weather and driving style.
Formula and assumptions reviewed October 2026 by the Calculyn team. How we build our calculators
Frequently asked questions
Why is my real MPG lower than the sticker?
Speed, AC use, short trips, tire pressure and cargo all reduce real-world fuel economy.