Translate a fuel rating between US mpg, imperial mpg, km/L and consumption per distance. Each result identifies which gallon definition it uses.
Convert an existing rating
Enter a positive rating and choose its exact unit. US mpg and imperial mpg describe different distances per gallon because the gallons have different sizes. Select L/100 km when the source gives fuel used per distance. The result includes all supported equivalents and a reference table.
To calculate an observed rating from a fill-up and distance traveled, use the Gas Mileage Calculator. To estimate a journey's fuel bill, use the Fuel Cost Calculator.
Why consumption conversions use division
Mpg and km/L put distance in the numerator: a higher number means more distance per unit of fuel. L/100 km puts fuel in the numerator: a lower number means less fuel for the same trip. This reversal requires a reciprocal, not a fixed multiplier.
The constants below follow exact mile and gallon definitions; the displayed constants are rounded for readability. The calculator retains full precision. Zero consumption would imply infinite distance per fuel, so zero and negative inputs are rejected.
Comparing vehicles and real trips
Converting a rating does not adjust the test cycle, road conditions, load, driving style or weather. Compare ratings measured on the same basis. Do not average mpg figures arithmetically across unequal journeys: combine total distance and total fuel first. MPGe uses an energy equivalence and belongs in the separate MPGe Calculator.
Natural Resources Canada explains fuel-rating units and reciprocal conversions.
Formula
L/100 km = 235.214583333... ÷ mpg (US)
L/100 km = 282.480936331... ÷ mpg (imperial)
km/L = 100 ÷ (L/100 km)
Examples
A US rating
30 US mpg is approximately 7.840486111 L/100 km, 12.75431122 km/L, and 36.02849777 imperial mpg.
A consumption rating
5 L/100 km is 20 km/L, approximately 47.04291667 US mpg.
Precision and definitions
Calculations retain unrounded values internally. Displayed digits do not increase the accuracy of measurements. NIST unit definitions provide the conversion reference.