Best measurement method
For a useful estimate, reset the trip counter after filling the tank, drive normally, then divide distance by the fuel added at the next fill-up. Short trips can be distorted by cold starts, traffic and partial fills.
Example
If you drive 420 miles and add 12 US gallons at the next fill-up, the trip fuel economy is 420 / 12 = 35 mpg. The same calculator can also show metric-style results when kilometers and liters are used.
Common mistakes
Do not mix imperial and metric units by accident. Also avoid relying on a single short trip if weather, traffic or towing made that trip unusual.
Limitations
Dashboard estimates and pump shutoff behavior can differ from actual fuel use. For a better average, compare several full-tank measurements over normal driving.
Last reviewed: 2026-05-17