MPG Calculator

Fuel efficiency comes down to two numbers worth tracking: miles per gallon and the cost per mile your vehicle racks up. With U.S. regular gasoline averaging $4.48 a gallon in the week of September 21, 2026 (EIA), those figures move from trivia to budgeting tools, and a sudden drop in MPG can be an early sign that something mechanical needs attention. Watched over time, they inform both how you drive and when you service the car, which can add up to hundreds of dollars a year.

The arithmetic is direct. MPG comes from dividing the total miles driven by the gallons consumed, and cost per mile comes from dividing what you paid for the fuel by those same miles. Drive 300 miles on 10 gallons that cost $41.50, for example, and you land at 30 MPG and $0.138 per mile.

Clean inputs make the difference between a useful number and a misleading one. Filling the tank all the way each time you log gallons gives the most reliable average, because partial fills throw the figure off. It's worth remembering that aggressive driving, heavy loads, and underinflated tires all eat into MPG, so keep those conditions in mind when you read what the calculator returns.