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Fuel Economy Converter – L/100 km, km/L and MPG

Compare cars from different countries with this fuel economy converter for L/100 km, km/L, US MPG and UK MPG.

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Common conversions

From unit Value To unit Result
Litres per 100 kilometres (L/100 km) 5 Miles per US gallon (mpg US) 47.0429
Litres per 100 kilometres (L/100 km) 8 Miles per US gallon (mpg US) 29.4018
Miles per US gallon (mpg US) 30 Litres per 100 kilometres (L/100 km) 7.8405
Miles per UK gallon (mpg UK) 40 Miles per US gallon (mpg US) 33.307
Kilometres per litre (km/L) 20 Litres per 100 kilometres (L/100 km) 5

How to use the Fuel Economy Converter

  1. 1 Enter the fuel economy figure, for example 6.5.
  2. 2 Choose the unit it is given in: L/100 km, km/L, US MPG or UK MPG.
  3. 3 Choose the unit you want to compare with and read the result.

Two ways to express fuel economy

Fuel economy can be stated as consumption or as efficiency, and they work in opposite directions:

  • Litres per 100 km (L/100 km) – how much fuel a car uses to cover a distance. Lower is better. Used in Europe, Canada, Australia and China.
  • Kilometres per litre (km/L) – how far a car goes on one litre. Higher is better. Common in Japan, India and Latin America.
  • Miles per gallon (MPG) – how far a car goes on one gallon. Higher is better. Used in the US and the UK, but with different gallons.

Because L/100 km is the inverse of distance per volume, the conversion is not a simple factor. The converter uses 100 ÷ value to switch between L/100 km and km/L.

US MPG versus UK MPG

A UK (imperial) gallon is 4.546 litres and a US gallon is 3.785 litres, so the same car shows a higher MPG figure in the UK. 40 UK MPG is about 33.3 US MPG, and 30 US MPG is 36 UK MPG. Always check which gallon a review or brochure uses.

Formulas

  • US MPG = 235.215 ÷ L/100 km
  • UK MPG = 282.481 ÷ L/100 km
  • L/100 km = 100 ÷ km/L

For example, a car using 5 L/100 km achieves 20 km/L, 47.0 US MPG or 56.5 UK MPG.

Why L/100 km is easier for comparing savings

Improving from 10 to 20 MPG saves more fuel than improving from 30 to 50 MPG over the same distance. In L/100 km the effect is obvious: 23.5 to 11.8 L/100 km saves about 11.8 litres, while 7.8 to 4.7 L/100 km saves just 3.1 litres. Consumption figures make it easier to estimate fuel costs: multiply L/100 km by your annual distance divided by 100 and by the fuel price.

Electric cars

Electric vehicles use kWh per 100 km or miles per kWh instead. Some US labels show MPGe, which assumes 33.7 kWh of electricity is equivalent to one US gallon of petrol.

Sources

Conversion factors follow the SI definitions in the BIPM SI Brochure and the exact factors for US customary and imperial units in NIST Special Publication 811. Official US fuel economy ratings are published on fueleconomy.gov.

Frequently asked questions

How do I convert L/100 km to MPG?

Divide 235.215 by the L/100 km figure for US MPG, or 282.481 for UK MPG. For example, 8 L/100 km is 29.4 US MPG.

Is lower or higher better in L/100 km?

Lower is better: L/100 km measures how much fuel is used, while km/L and MPG measure distance per fuel, where higher is better.

Why is UK MPG higher than US MPG?

A UK gallon is about 20% larger than a US gallon, so a car travels further on it.

What is 30 MPG in L/100 km?

30 US MPG is 7.84 L/100 km; 30 UK MPG is 9.42 L/100 km.

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