How it works
How to calculate it
The calculator applies the values you enter to this formula:
MPG = miles driven ÷ gallons used.
How to use this calculator
- Fill the tank consistently.
- Reset or record the trip odometer.
- At the next fill-up, divide miles driven by gallons added.
Worked example
Driving 360 miles and adding 12 gallons at the next fill-up equals 30 MPG.
Important assumptions
- For best results, fill the tank to a similar level each time.
- Use trip-odometer miles between fill-ups.
- One tank can be distorted by driving conditions or pump shutoff variation.
Common mistakes to avoid
- Using tank capacity instead of gallons added.
- Mixing partial fill-ups.
- Judging long-term economy from one unusual tank.
Method reviewed June 10, 2026. Prices and rates are user-provided defaults and should be replaced with local values.