MPG Converter

Created by Piotr Małek
Reviewed by Jack Bowater
Last updated: Aug 30, 2023

Table of contents:

This Miles Per Gallon (MPG) converter enables you to quickly and easily swap between units used in fuel economy conversions. The three available units in this MPG converter are:

  • miles per US gallon
  • miles per UK gallon
  • liters per 100 kilometer

Keep in mind that these units are inversely proportional (that is, as one decreases, the other increases, and vice versa). An efficient car consumes a low amount of gasoline per 100 kilometers, but can travel many miles on a gallon. This MPG converter can serve as a useful tool when ordering a car from abroad. Make sure you also have it with you when you are traveling in a country with different fuel economy units as the differences between them are quite significant. Our gas calculator is closely related to these issues, as it lets you calculate the total cost of a car trip based on the mileage, distance and gas price.

Fuel economy conversion

Fuel economy is the relationship between the distance a vehicle travels and the amount of fuel it consumes. When calculating, it's important to distinguish between the US and imperial gallon as they represent different values. US gallons are used mostly in the Unites States (unsurprisingly) but also in some Caribbean and Latin American countries. Imperial gallon is a unit you can encounter in some Commonwealth countries such as the United Kingdom and Canada. Liters per 100 kilometers are used almost anywhere else on the planet.

Another important difference is between the measurement systems - when using miles (either imperial or US) per gallon, the higher the value, the more efficient the vehicle is. On the other hand, those using liters per 100 km usually hope for a lower score as it results in smaller gas bills. 1 liter per 100 kilometers equals 235.2 US MPG or 282.5 Imperial MPG. At the same time 1 US MPG equals 235.2 liters per 100 km. 1 US MPG = 1.201 UK MPG while 1 UK MPG is 0.8327 US MPG. These are the basic equations of fuel economy conversion.

If you want to go deeper into the topic, check out our speed calculator which deals with the trinity of time, distance and speed; while the acceleration calculator deals with how the velocity changes over time or how much a given force moves an object with a given mass by.


How to improve fuel economy?

Here are some tips you could use for improving fuel economy:

  1. Drive at speeds around 60–65 mph (95–100 km/h). Cars consume fuel more efficiently at that speed.
  2. Keep your tires full of air.
  3. At speeds above 50 mph (80 km/h), it is highly recommended to close the windows and use the AC instead, as wind increases resistance and makes the car consume more fuel.

What is a good fuel economy?

There are different ways to measure fuel economy.

  • "The lower, the better" if we are using liters per 100 km (ℓ/100 km).
  • "The higher, the better" if we use the English metric system (miles per gallon or mpg).

Famous car blogs indicate that anything less than 6 liters per 100 km is excellent. Omnicalculator's fuel economy conversion tool shows that 6 ℓ/100 km equals 39.2 US mpg.

How to find out the fuel economy of my car?

Here is a practical method to calculate fuel economy:

  1. Set the odometer to zero. Mark where the fuel tank needle lies.
  2. Fill the tank with gas, recording how many gallons you've thrown in. Check the fuel tank needle again.
  3. Drive a bit, then stop the car when the needle is back to its position of Step 1, meaning you've consumed all the gas you've added in Step 2.
  4. Divide the miles you've drived by the spent gallons. That's your fuel economy in mpg.

How to convert fuel economy from US mpg to liters per km?

  1. Pick the US mpg (miles per US gallon). Multiply it by 1.609 to convert the miles to kilometers.
  2. Divide the result above by 3.78 to convert the US gallons to liters, and...
  3. Voilá! The result is the fuel economy expressed in km per liter. Multiply by 100 to convert it to the 100 km/ℓ measure.
Piotr Małek
US mpg
UK mpg
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