Fuel Economy Converter

Convert fuel consumption between miles per gallon and liters per 100 km — 30 US mpg is 7.84 L/100 km and 5 L/100 km is 56.5 UK mpg — plus km/L and gallons per 100 miles.

This tool runs entirely in your browser.

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How to use the Fuel Economy Converter

1Enter a value.
2Choose the unit to convert from and to (use ⇄ to swap).
3Read the result, or scan the table for every unit at once.

What is the Fuel Economy Converter?

Miles per gallon and km per liter measure distance per fuel (higher is better), while L/100 km and gallons per 100 miles measure fuel per distance (lower is better). Converting between them is a reciprocal, not a multiplication: L/100 km = 235.21 ÷ US mpg.

UK and US mpg differ because the imperial gallon (4.546 L) is about 20 % bigger than the US gallon (3.785 L), so the same car shows a higher mpg figure in the UK: 40 UK mpg is only 33.3 US mpg.

Results show up to 10 significant digits; very large or small values switch to scientific notation.

Frequently asked questions

How do I convert mpg to L/100 km?

Divide 235.21 by US mpg (or 282.48 by UK mpg). For example, 30 US mpg = 235.21 ÷ 30 = 7.84 L/100 km.

Why do small mpg gains matter more for thirsty cars?

Because fuel used is the reciprocal. Going from 10 to 12 mpg saves more fuel per mile than going from 40 to 50 mpg — L/100 km shows this directly.

Is the Fuel Economy Converter free and private?

Yes. The Fuel Economy Converter is free, needs no account, and runs entirely in your browser. What you type is never sent to a server or stored.

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