Free vehicle tool
Gas mileage calculator
Calculate your car's real-world miles per gallon (MPG) from the miles you've driven and the gallons you've used.
Calculate your MPG
Enter the distance driven between fill-ups and the gallons added at your next fill-up. Use miles and US gallons.
If you track your odometer, subtract its reading at the first fill-up from its reading at the next fill-up to find miles driven.
How do you calculate MPG?
Divide the miles you drove by the gallons of fuel you used. For example, 300 miles divided by 10 gallons equals 30 miles per gallon.
- Fill the tank completely and record your odometer reading (or reset your trip meter).
- Drive as you normally would, then fill the tank completely again.
- Subtract the first odometer reading from the second. Enter those miles and the gallons shown on the second receipt above.
For a more representative result, repeat this across several fill-ups and divide the total miles by the total gallons. Don't average the individual MPG readings if fill-up sizes differ.
Why might my MPG differ from the EPA rating?
EPA figures are standardized estimates. Your measured MPG can change with traffic, speed, weather, hills, tire pressure, vehicle load, and driving style. An incomplete fill-up can also distort a single reading.
If your fuel economy has changed noticeably, check basic maintenance such as tire pressure and your vehicle's service schedule. A single fill-up alone does not diagnose a mechanical problem.
Need a vehicle's EPA-rated MPG by year, make, and model instead? Our gas cost calculator includes a vehicle lookup. You can also use your measured MPG there to budget for a drive.
If you're in Swerve's service area, you can explore maintenance service estimates.