Fuel Efficiency Converter
Convert between mpg (US/UK), km/L, and L/100km — handles inverse units correctly.
Note: L/100km is a consumption rate (lower = better). All other units are efficiency rates (higher = better). They have an inverse relationship.
Frequently asked questions
Why does a better car show a lower L/100km but a higher mpg?
L/100km is a consumption rate — it tells you how much fuel you burn per 100 km. Lower is better. mpg (miles per gallon) is an efficiency rate — how far you travel per unit of fuel. Higher is better. They are mathematical inverses: a car that uses 5 L/100km gets about 47 mpg (US), while one using 10 L/100km gets about 24 mpg (US).
Why does UK mpg look better than US mpg for the same car?
A UK gallon is 4.546 litres vs a US gallon of 3.785 litres — about 20% larger. So you can travel further per UK gallon, making the mpg number bigger. A car achieving 40 mpg (US) gets approximately 48 mpg (UK). Always check which gallon a fuel economy figure uses.
What is a typical fuel efficiency for a modern car?
A typical modern petrol city car achieves 5–7 L/100km (40–47 mpg US). A large SUV might use 10–14 L/100km (17–24 mpg US). Hybrid vehicles commonly achieve 4–5 L/100km (47–59 mpg US). Plug-in hybrids and EVs are measured in kWh/100km or miles per kWh rather than fuel consumption.
