Fuel Economy Converter

Fuel economy: L/100km, km/L, miles per gallon (US and UK).

л/100км
L/100 km
км/л
km/L
mpg US
mpg (US)
mpg UK
mpg (UK)

The fuel economy converter translates values between liters per 100 km (L/100km), kilometers per liter (km/L), and miles per gallon — calculated separately for the American (US) and British (UK) gallon. Type a number into any field and the other units update instantly.

Conversion is useful when comparing fuel economy for foreign cars: the US and UK express efficiency in miles per gallon (mpg), while many other countries use liters per 100 km. Here's the key catch: L/100km and mpg are inversely related — the lower the L/100km, the higher the mpg, meaning the car is more efficient. You can't just "convert" them with simple multiplication; the math has to account for that inverse relationship. Also note the gallon difference: 1 US gallon ≈ 3.785 L, 1 UK gallon ≈ 4.546 L, so mpg (US) and mpg (UK) are different numbers for the same car.

For example, 8 L/100km ≈ 29.4 mpg (US). Everything is calculated right in your browser, instantly, with no data sent anywhere.

Frequently asked questions

Using a constant: mpg (US) = 235.21 / (L/100km). For example, 8 L/100km ≈ 29.4 mpg US.
The British gallon (4.546 L) is larger than the American one (3.785 L), so for the same fuel consumption, mpg UK is always about 1.2 times higher than mpg US.
For L/100km, lower is better (less fuel used). For km/L and mpg, it's the opposite: higher is better (you go further on the same amount of fuel).

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