How to use this calculator
Replace the example values with your own measurements or specifications. Keep the units shown beside each label. Results update as you type; reset restores the example.
Fill to the first automatic shutoff, reset the trip meter, then refill the same way next time. Record the distance and fuel added. Multiple tanks reduce the effect of pump shutoff variation. Never top off the tank.
The formula
A worked example
Driving 360 miles and refilling with 12 U.S. gallons gives 30 U.S. mpg, about 7.84 L/100 km. For a metric example, 600 km and 48 liters gives 8 L/100 km, 12.5 km/L, 29.40 U.S. mpg, or 35.31 UK mpg.
Common questions
Can I average several tanks?
Add the distances and fuel volumes using consistent units, then divide total distance by total fuel. An unweighted average of tank MPG figures can give the wrong result.
Are U.S. and UK gallons the same?
No. One U.S. gallon is 3.785411784 liters; one Imperial gallon is 4.54609 liters. Choose the unit actually recorded at the pump.
Can I enter a partial refill?
For the full-to-full method, measure between comparable full fills. A partial refill alone does not tell you how much fuel was consumed over the recorded distance.
Does changing units convert the entered numbers?
No. The selected unit describes the number you enter. Enter the actual reading in that unit. All four result units update together.
Sources & calculation method
Related guidance: U.S. DOE / EPA: fuel economy and driving. Accessed September 9, 2026. The equation above describes this tool’s model; the reference provides practical context and does not endorse this site.
Prepared with AI assistance. Formula examples and input validation have automated checks. This page has not received an independent automotive professional review. Read our review standards.