How to Convert Miles Per Gallon to Km Per Litre

by Jonathan Spiegel

Converting miles per gallon (mpg) to kilometers per litre (km/l) is a simple mathematical process. It can be done in a few easy steps. The only mathematical skills required are multiplication and division, and the use of a simple hand calculator will make things even easier. Miles per gallon (mpg) is determined by dividing the number of miles traveled by the amount of fuel consumed, in gallons. Kilometers per litre (km/l) is determined by dividing the kilometers traveled by the number of litres consumed. For a sample calculation, use 25 miles per gallon as an example, and round all numbers to 2 decimal places.

Convert miles into kilometers. Since a kilometer is shorter than a mile, and there are 1.61 kilometers in every mile, you will have to multiply to get the answer. Doing the math (25 x 1.61 = 40.25) shows that 25 miles is equivalent to 40.25 kilometers.

Convert gallons into litres. Since a litre is smaller than a gallon, you must again multiply to get the answer. There are 3.79 litres in every gallon. Here the math is simple, because you are using only 1 gallon. 1 x 3.79 = 3.79, so a gallon of gas is equal to 3.79 litres.

Perform the calculation to determine how many kilometers are attributable to each litre of fuel consumed. Since you have determined that the vehicle traveled 40.25 kilometers on 3.79 litres of fuel, simple division will tell you how many kilometers are traveled on 1 litre. 40.25 ÷ 3.79 = 10.62. 25 mpg is therefore equivalent to 10.62 km/l.

Create a conversion factor, based on the above calculations. One mile is equal to 1.61 kilometers. One gallon is equal to 3.79 litres. Simple division will give you a conversion factor. 1.61 ÷ 3.79 = 0.425. This means that 0.425 km/l equals 1 mpg. You can use the newly calculated conversion factor by multiplying miles per gallon by 0.425. Checking your previous work, 25 mpg x 0.425 = 10.62 km/l, which is identical to the answer in the three-step calculation above.

Tip

  • check Check you fuel mileage every few tankfuls of gas. If mileage decreases, it may be a sign of developing car trouble.

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About the Author

Jonathan Spiegel has been involved in the automotive and motorcycle industries for over 25 years. He has authored numerous technical articles and professional papers. Spiegel currently works as a freelance journalist and small business consultant based in Kona, Hawaii. He holds a Bachelor of Science in applied physics from Georgia Institute of Technology.