Fuel Economy Unit Converter

Compare distance-per-volume and volume-per-distance fuel-economy conventions used across countries. US mpg uses the 3.785411784-liter US gallon, while imperial mpg uses the larger 4.54609-liter imperial gallon; this tool converts units only and does not predict a vehicle’s real efficiency or fuel cost. Calculate it clearly with Figur.

How the fuel economy unit converter works

Compare distance-per-volume and volume-per-distance fuel-economy conventions used across countries. US mpg uses the 3.785411784-liter US gallon, while imperial mpg uses the larger 4.54609-liter imperial gallon; this tool converts units only and does not predict a vehicle’s real efficiency or fuel cost.

Method and assumptions

Figur normalizes distance-per-volume units to km/L. For L/100 km it applies the reciprocal relationship 100 ÷ km/L. US mpg uses 1 US gal = 3.785411784 L and imperial mpg uses 1 imperial gal = 4.54609 L.

  • The mile is the exact international mile of 1.609344 km.
  • The entered value is positive; zero does not represent a convertible fuel economy and is rejected to avoid undefined division.
  • Conversion changes the unit convention of a known efficiency; it does not estimate how a real vehicle will perform.

Unit conversion only. It does not include live fuel prices, trip costs, vehicle-specific predictions, or electric-vehicle energy economy.

Sources and references

Worked example

Convert 30 US mpg to liters per 100 kilometers.

30 mpg (US) equals approximately 7.84048611111 L/100 km.

Frequently asked questions

Why is L/100 km reciprocal?

MPG and km/L rise when efficiency improves, but L/100 km falls. Figur converts through km/L and uses 100 ÷ km/L when either side is L/100 km.

Are US mpg and imperial mpg the same?

No. Both use the same international mile, but an imperial gallon is larger than a US gallon, so the same physical fuel economy has a higher imperial-mpg number.

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