Fuel economy converter (mpg, km/L, L/100km)
Convert fuel economy between km/L, miles per gallon (mpg) and liters per 100 km.
mpg uses the US gallon (3.785 L). Note that L/100km is inverted: the LOWER, the more efficient.
How the calculation works
The three scales measure the same thing differently: 1 mpg (US) = 0.4251 km/L and L/100km = 100 ÷ km/L. E.g., 30 mpg = 12.75 km/L = 7.84 L/100km. km/L and mpg rise with efficiency; L/100km falls.
Examples
- 30 mpg = 12.75 km/L = 7.84 L/100km.
- 10 km/L = 10 L/100km (where the two scales meet).
Frequently asked questions
US or imperial gallon?
We use the US gallon (3.785 L). The imperial gallon (UK) is 4.546 L — imperial mpg figures are ~20% "higher".
Why does L/100km fall as economy rises?
Because it measures the opposite: liters to go 100 km. Fewer liters = more efficient. km/L and mpg rise with efficiency.
Which scale does Europe use?
Mostly L/100km. Brazil uses km/L; the US, mpg. This tool converts among all three.
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Updated on July 5, 2026 · by Rafael Rossi · Methodology & sources