Fuel Economy Converter
Interactive StudioConvert between km/L, L/100km, US mpg, UK mpg, and mi/L with built-in trip fuel cost estimator. Instant feedback with zero server storage.
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About Fuel Economy Converter
Fuel economy measures automotive energy efficiency. Unlike standard distance conversions, fuel efficiency units operate across two reciprocal paradigms: • Distance-per-Fuel (mpg, km/L): Higher values indicate superior fuel efficiency. • Fuel-per-Distance (L/100km): Lower values indicate superior fuel economy.
Furthermore, US and UK imperial gallons differ in liquid volume (1 US Gallon = 3.785 L vs 1 UK Gallon = 4.546 L), resulting in higher numeric mpg ratings in the UK for the same physical vehicle efficiency.
How to use Fuel Economy Converter
- Type the value you want to convert.
- Choose the unit you are converting from and the unit you want, such as mpg (US or UK), km/L or L/100km.
- Read the converted value instantly. Swap the units to convert the other way.
- Copy the result, or check other units listed in the results grid.
Worked examples
Input: 30 mpg (US) to L/100km
Result: About 7.84 L/100km.
Input: 8 L/100km to mpg (US)
Result: About 29.4 mpg.
Input: 30 mpg (UK) to L/100km
Result: About 9.42 L/100km. A UK gallon is bigger, so the same mpg means more fuel used per 100 km than a US mpg figure.
Background
mpg and km/L measure distance per unit of fuel, so higher is better. L/100km measures fuel per distance, so lower is better. The two are reciprocal: L/100km = 235.215 / mpg(US), and 282.481 / mpg(UK).
A US gallon is 3.785 L and a UK gallon is 4.546 L, which is why the same car has a higher mpg rating in the UK.
Common mistakes
- Comparing US and UK mpg directly. A UK mpg number is about 20% higher for the same car.
- Using straight multiplication between L/100km and mpg. The relationship is inverse.
- Assuming a lower number is better for mpg. It is better for L/100km only.
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