Fuel Economy Converter: Units, Formulas, and Examples
Compare fuel economy in US MPG, Imperial MPG, kilometers per liter, and liters per 100 kilometers.
How to convert fuel economy
L/100 km = (100 × 3.785411784 ÷ 1.609344) ÷ US MPG. For Imperial MPG, replace the gallon volume with 4.54609 liters.
Keep the source and target definitions consistent, apply the conversion to the original value, and round the final answer to the precision needed for your calculation.
Understanding fuel economy units
Distance per fuel and fuel per distance are reciprocal measurements. Higher MPG or km/L means better fuel economy; lower L/100 km means less fuel consumed. US and Imperial gallons are different sizes.
Worked fuel economy examples
30 US MPG is approximately 7.8404861111 L/100 km and 12.7543112229 km/L.
Frequently asked questions
Which definitions should I use?
A zero or negative value cannot describe a finite, positive fuel economy. This converter requires a value greater than zero.
Why do displayed results sometimes differ slightly?
Intermediate arithmetic uses browser floating-point numbers. Display rounding and the precision of an original measurement can affect the last digits. The unit conversion does not improve the accuracy of a measured value.
Does converting back recover the original value?
Using the unrounded result normally recovers the original quantity within floating-point precision. Copying a rounded number can introduce a small difference.
How are the unit definitions documented?
For physical unit definitions and conversion factors, see the NIST conversion reference. The Canadian Fuel Consumption Guide also explains the reciprocal relationship between MPG and L/100 km.