Fuel Economy Converter
Enter a fuel economy figure, choose the unit it is in and the unit you want. You get the converted figure and the same economy in all four units.
Your numbers
How we calculate it
Everything goes through kilometers per liter, using exact constants: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 liters and 1 UK (imperial) gallon = 4.54609 liters. Miles per gallon multiplies the kilometers per liter by the gallon size and divides by the length of a mile. Liters per 100 km is 100 divided by the kilometers per liter, so it runs the other way: a lower number is better.
So 30 miles per US gallon is 12.7543 km per liter, 36.03 miles per UK gallon and 7.84048611 liters per 100 km.
Assumptions and limits
- Miles per gallon and liters per 100 km move in opposite directions, so doubling the mpg halves the liters per 100 km.
- A US gallon is smaller than a UK gallon, so the same car has a higher figure in miles per UK gallon, by about 20%.
- The value must be above zero, because zero fuel economy has no meaning.
Frequently asked questions
How do I convert mpg to liters per 100 km?
Divide 235.215 by the miles per US gallon. 30 mpg is 235.215 ÷ 30 = 7.84 liters per 100 km. The same formula works to go back.
Why are US and UK miles per gallon different?
The gallons are different sizes. A UK gallon is 4.54609 liters and a US gallon is 3.785411784 liters, so a UK figure is about 20% higher for the same car.
Is a lower L per 100 km better?
Yes. It is the fuel needed for a fixed distance, so a smaller number means a more efficient car. Miles per gallon is the opposite: bigger is better.
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Worked example (a fixed example using the starting numbers, it does not change as you type)
Inputs: Fuel economy = 30; From = miles per US gallon (mpg (US)); To = liters per 100 kilometers (L/100 km).
- Result 7.84048611111 L/100 km
- Conversion 30 mpg (US) = 7.84048611111 L/100 km
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