Two ways to describe fuel economy
Fuel economy can be stated as distance per amount of fuel or as fuel per distance. Americans and Britons use miles per gallon, and Japan and India use kilometers per liter: higher numbers mean a more efficient vehicle. Europe, Canada and Australia use liters per 100 kilometers, the fuel needed to cover a fixed distance: there, lower is better.
How to use this converter
Type a value in any field and the others update as you type. Make sure you pick the right gallon: US and UK mpg differ by about 20% for the same car. Each pair below the converter has its own page with the formula, an example and a chart.
The formulas
Because one scale is the inverse of the other, the conversion is a division:
- L/100 km = 235.215 ÷ US mpg
- L/100 km = 282.481 ÷ UK mpg
- L/100 km = 100 ÷ km/L
- US mpg = 2.35215 × km/L
- UK mpg = 1.20095 × US mpg
The mpg illusion
On an mpg scale, equal steps do not save equal amounts of fuel. Over 10,000 miles, a car at 10 mpg burns 1,000 gallons and one at 20 mpg burns 500, saving 500 gallons. Going from 30 to 40 mpg saves only about 83 gallons over the same distance. Replacing a very thirsty vehicle therefore saves far more than fine-tuning an efficient one. L/100 km avoids this trap because fuel use is directly proportional to it.
Comparing ratings
Official figures depend on the test cycle. US EPA ratings, the European WLTP cycle and older NEDC figures give different results for the same car, with NEDC the most optimistic. Convert units to compare, but compare like with like when you choose a vehicle.
Tips
To estimate a trip’s fuel cost, convert to L/100 km or gallons per 100 miles, multiply by the distance in hundreds and by the fuel price.
The units in detail
What is a kilometer per liter?
Kilometers per liter tell how far a vehicle travels on one liter of fuel, like mpg with metric units. Japan, India and much of Latin America use it. Higher is better: 15 km/L is about 35 US mpg.
What is a liter per 100 kilometers?
Liters per 100 kilometers measure how much fuel a vehicle burns over a fixed distance. Europe, Canada and Australia use it on window stickers. Lower is better, and fuel cost scales directly with it: a car at 5 L/100 km burns half as much as one at 10.
What is a mile per gallon?
Miles per US gallon are the fuel economy unit of US window stickers and EPA ratings. Higher is better. Because it is a distance per volume, savings are not linear: going from 10 to 20 mpg saves far more fuel than going from 30 to 40 mpg.
What is a mile per imperial gallon?
UK mpg use the imperial gallon of 4.546 liters, 20% larger than the US gallon. The same car therefore shows a higher figure in Britain: 40 UK mpg is only about 33 US mpg.