Calculate fuel economy from two odometer readings and the fuel added at the second fill. Optional fuel price adds fill cost and unit-cost results.
How to use this calculator
Use the distance driven and fuel used over the same trip or fill-up interval. Select the correct units, especially US versus Imperial gallons. For a steadier estimate, combine distance and fuel across several fills rather than averaging the displayed mileage figures.
Examples
U.S. default
Driving 360 miles on 15 gallons gives 24 mpg, or 9.8 L/100 km. At $3 per gallon, the fill costs $45 and fuel costs $0.125 per mile.
Formula
In U.S. units, mpg = miles traveled / gallons. In metric units,
km/L = kilometers traveled / liters and L/100 km = 100 / (km/L).
Measurement limits
Tank-to-tank mileage is most useful across several complete fill-ups. Pump shutoff, slope, temperature, partial fills, odometer error, and vehicle display rounding can move a single result. Record the odometer and actual dispensed fuel consistently; do not infer a mechanical fault from one tank alone. EPA labels are standardized comparisons rather than a promise of an individual driver's result.
Compare an existing fuel rating
If you already have an economy rating, the Fuel Economy Converter translates US mpg, imperial mpg, km/L and L/100 km. Always check the gallon definition. Consumption per distance uses a reciprocal relationship, so higher mpg corresponds to lower L/100 km.