Fuel Economy Calculator

For a refill measurement, start and finish at comparable fill levels, note the distance covered between them, and use the refill amount as an estimate of fuel consumed. Inconsistent fill levels, inaccurate meters, or omitted refills affect the answer. Tank capacity alone does not tell you how much fuel was used on a particular trip.

The exact definitions used here are 1 international mile = 1.609344 km, 1 US liquid gallon = 3.785411784 L, and 1 Imperial gallon = 4.54609 L. US dry gallons and nautical miles are not supported. For a rate in km/L, multiply by liters per gallon and divide by 1.609344 to obtain that gallon system's mpg. L/100 km equals 100 divided by km/L.

Every active input must be greater than zero, with at most 64 characters, 15 integer digits, and 10 decimal places. Expressions, scientific notation, and units inside numeric fields are not accepted. Unused mode fields are disabled and do not affect the result. This tool excludes zero fuel use because a reciprocal fuel economy rate would not be finite.

Unit conversions and arithmetic retain exact fractions. Only the final display is rounded, with halfway values rounded away from zero and trailing zeros removed. ≈ marks a rounded value; a notice explains when a positive rate rounds to zero. Changing the main unit or precision reformats the existing result without adding a recent-calculation entry.

This is a distance-and-volume calculation for the values you provide, not an official test-cycle rating or an estimate of future performance. It does not calculate electric-vehicle MPGe, emissions, fuel prices, or measurement uncertainty. More displayed digits do not make the measurements more accurate.

References: FuelEconomy.gov — calculating MPG from distance and refills, US EPA — fuel economy and consumption on vehicle labels, and NIST Guide to the SI — unit conversion factors.