Miles per Gallon (US) to Kilometers per Liter Converter | mpg (US) to km/L

What this converter does

US fuel economy is given in miles per US gallon, but much of the world measures it in kilometres per litre. This converter takes a figure in US mpg and turns it into km/L. Enter the mpg value and read off the km/L, so an American economy figure can be read in metric terms.

The conversion factor

To go from US mpg to kilometres per litre you multiply:

km/L = mpg (US) × 0.425144

That factor rolls together two conversions, miles into kilometres and US gallons into litres, into a single step. It is worth being clear that this uses the US gallon of about 3.785 litres, not the larger UK one, so make sure the figure you start with really is US mpg.

Two units, the same idea

These two units measure economy the same way round, which keeps things simple. Both miles per gallon and kilometres per litre are distance covered per unit of fuel, so a higher number means a more efficient car in either one. The conversion is just a change of units, not a change of meaning. That is a small but useful thing to know, because some metric economy figures, like litres per 100 kilometres, run the other way, where lower is better, and km/L is not one of those.

A worked example

Say a car is rated at 32 mpg in the US and you want that in kilometres per litre.

• 32 × 0.425144 = 13.6 km/L

So 32 US mpg is about 13.6 km/L. In a market that quotes km/L, that is the figure you would compare against other cars, and it sits in the middle of the range for an ordinary petrol car, neither thirsty nor especially frugal.

Common mpg (US) values in km/L

As anchors, 30 mpg US is about 12.75 km/L, and a frugal 50 mpg US comes out near 21 km/L.

Where it helps

This is for carrying a US economy figure into a metric setting. Many countries, especially across Asia, quote fuel economy in km/L, so converting lets you line a US-rated car up against locally quoted ones. It helps anyone comparing an American figure with metric data, reading specs for a model sold in several markets, or simply preferring to think in kilometres and litres. Since both units run the same way, the comparison is direct once the figure is converted.

Questions people ask

How do I convert US mpg to km/L?

Multiply the US mpg figure by 0.425144. The factor combines the mile-to-kilometre and US-gallon-to-litre conversions in one step.

Does it use the US or UK gallon?

The US gallon, about 3.785 litres. If your figure is in UK mpg, it needs a different factor, so be sure which gallon the mpg refers to.

Is a higher km/L better?

Yes. Like mpg, kilometres per litre measures distance per unit of fuel, so a higher number means a more efficient car.

References

1. National Institute of Standards and Technology (NIST), Special Publication 811, Guide for the Use of the International System of Units (gallon definitions and unit conversions). https://www.nist.gov/pml/special-publication-811
2. U.S. Department of Energy and EPA, fueleconomy.gov (fuel economy ratings and information). https://www.fueleconomy.gov/