Fuel Economy Converter
Convert fuel economy between MPG (US), MPG (UK), kilometers per liter, and liters per 100km.
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MPG and L/100km measure the same thing in opposite directions: MPG is distance per unit of fuel (higher is better), L/100km is fuel per unit of distance (lower is better). That inverse relationship is why a straight multiplier can't convert between them, and why this conversion looks different from a typical unit converter under the hood. US and UK gallons are also different sizes (a UK gallon is about 20% larger), which is why MPG (US) and MPG (UK) for the same car are different numbers.
Frequently asked questions
Why is converting MPG to L/100km not just simple multiplication?+
MPG measures distance per unit of fuel (higher is better), while L/100km measures fuel per unit of distance (lower is better), an inverse relationship. A straight multiplier can't convert between an inverse pair of units the way it can for, say, meters and feet.
Why are US and UK MPG different for the same car?+
A US gallon (3.785 liters) and a UK imperial gallon (4.546 liters) are different sizes, about 20% apart. The same actual fuel efficiency produces a higher MPG (UK) number than MPG (US), purely because of the different-sized gallon, not because the car performs differently.
Which unit is most common where?+
MPG (US) in the United States, MPG (UK) historically in Britain (though L/100km is now common there too), and L/100km across most of Europe and Canada.