In the United States, fuel consumption rates are expressed in miles per gallon. In Europe and other countries throughout the world, the accepted standard is kilometers per liter. If you need to calculate the fuel efficiency of your car in kilometers per liter, or if you want to covert an established miles-per-gallon rate to kilometers per liter, the process is straightforward and easy to understand.
Fill your gas tank and mark down the number of kilometers on your odometer. If the dial readout is in miles, multiply the figure by 1.609 to convert it to kilometers.
Make note of your odometer reading again when the gas tank runs out. Convert it to kilometers if necessary.
Subtract the first reading from the second and divide it by the number of liters in your gas tank. The resulting number will be your fuel consumption in kilometers per liter. If your gas tank capacity is listed in gallons, multiply it by 4.546 to convert the amount to liters.
Take an established miles-per-gallon fuel consumption rate and convert it to kilometers per liter by multiplying the rate by .425. For example, if your vehicle is able to drive 30 miles per gallon of gas, multiply 30 by .425 and you will have the kilometers-per-liter equivalent: 12.75.
