The conversion between miles per gallon (mpg) and kilometers per liter (km/L) can be tricky since you’re working with four units – miles, kilometers, gallons, and liters. However, once you learn the few steps it takes, you’ll kick yourself for not realizing how easy it is. 

There are two methods by which you can do it, the step-by-step method and the conversion ratio method, both of which will be explained in this article. 

Of course, you can also use an online conversion tool. Still, it doesn’t hurt to learn how to do it yourself since understanding the why behind the how will allow you to apply the same principles to other conversions.

So without further ado, let’s dive right in. 

There are two methods to convert miles per gallon (mpg) to kilometers per liter (km/L). The first method is a step-by-step process which is as follows:

  • Step 1: Multiply the miles by 1.609 to convert it into kilometers
  • Step 2: Divide the value by 3.785 to convert the answer into liters

The second method involves using a conversion ratio. This simple formula requires you to multiply the miles per gallon by 0.425144. 

It should be noted that these calculations only apply to the US gallon. Converting the UK gallon into kilometers per liter follows the same procedure but uses a different value for the second step. Let’s explore these methods in more detail and see the differences between the US and UK gallons with examples.

Step-by-step method – US gallon

There are four separate measurement units in miles per gallon and kilometers per liter. You have miles and kilometers, which measure the distance traveled, and you have gallons and liters, which measure the volume of liquid (fuel). As such, you must make two calculations to convert both miles to kilometers and gallons to liters. 

The first step is to convert miles into kilometers. One mile is equal to 1.609 kilometers. Therefore, to convert miles to kilometers, you must multiply the miles by 1.609. 

Since you’ve converted miles into kilometers, the value will be expressed as kilometers per gallon. From here, you must convert the gallons into liters. Since one US gallon equals 3.785 liters, your current answer is measured in kilometers per 3.785 liters. Therefore, to convert it to 1 liter, you must divide the gallons by 3.785.

Once these steps have been completed, you will have reached your final answer expressed as kilometers per liter.

To summarise, the steps are as follows:

  • Step 1: Multiply the miles by 1.609 to convert it into kilometers
  • Step 2: Divide the value by 3.785 to convert the answer into liters

Now that you know the steps, let’s see them in action.

Example 1

Let’s start with an easy one and calculate 10 miles per gallon in kilometers per liter.

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 10 x 1.609 = 16.09 

Step 2: Divide the value by 3.785 to convert the answer into liters:

  • 16.09 / 3.78 = 4.257.

This means that 10 miles per gallon are equal to 4.257 kilometers per liter. That was easy enough, right? Let’s look at another example.

Example 2

How many kilometers per liter are 25 miles per gallon?

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 25 x 1.609 = 40.225

Step 2: Divide the value by 3.785 to convert the answer into liters:

  • 40.225 / 3.785 = 10.628

This means that 25 miles per gallon is equal to 10.628 kilometers per liter.

Example 3

What are 7 miles per gallon in kilometers per liter?

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 7 x 1.609 = 11.263

Step 2: Divide the value by 3.785 to convert the answer into liters:

  • 11.263 / 3.785 = 2.976

This means that 7 miles per gallon equals 2.976 kilometers per liter.

Step-by-step method - UK gallon

Doing this conversion is the same as shown above, but you substitute a different number for the second step. This is because the measurement for the UK gallon is bigger than the US gallon. As such, the entire process is as follows:

  • Step 1: Multiply the miles by 1.609 to convert it into kilometers
  • Step 2: Divide the value by 4.546 to convert the answer into liters

As you can see, you divide by 4.546 instead of 3.785. Let’s see some examples.

Example 1

What is 33 miles per gallon (UK) in kilometers per liter?

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 33 x 1.609 = 53.097

Step 2: Divide the value by 4.546 to convert the answer into liters:

  • 53.097 / 4.546 = 11.680

This means that 33 miles per gallon (UK) is equal to 11.680 kilometers per liter.

Example 2

How many kilometers per liter is 15 miles per gallon (UK)?

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 15 x 1.609 = 24.135

Step 2: Divide the value by 4.546 to convert the answer into liters:

  • 24.135 / 4.546 = 5.309

This means that 15 miles per gallon (UK) is equal to 5.309 kilometers per liter.

Example 3

What is 68 miles per gallon (US) in kilometers per liter?

Step 1: Multiply the miles by 1.609 to convert it into kilometers:

  • 68 x 1.609 = 109.412

Step 2: Divide the value by 4.546 to convert the answer into liters:

  • 109.412 / 4.546 = 24.068

This means that 68 miles per gallon (UK) is equal to 24.068 kilometers.

Conversion ratio method

Instead of doing the two-step calculation, there is a quick shortcut: the conversion ratio method. All you have to memorize is the conversion ratio between mpg and km/L and multiply it by the mpg.  

US gallon

One mile per gallon is equal to 0.425144*, which is the conversion ratio. Therefore, to convert miles per gallon to kilometers per liter, do the following calculation:

  • Miles per gallon x 0.425144 = kilometers per liter

UK gallon 

One mile per gallon (UK) is equal to 0.354006*, which is the conversion ratio. Therefore, to convert miles per gallon to kilometers per liter, do the following calculation:

  • Miles per gallon x 0.354006 = kilometers per liter

*You may notice that these figures are slightly different from the value you get when using the step-by-step method. This is simply due to rounding up the numbers involved in the calculations.

Conversion table

Miles per gallon (US)Kilometers per literMiles per gallon (UK)Kilometers per liter
10.42514410.354006
20.85028720.708012
31.27543131.062018
41.70057541.416024
52.12571951.77003
62.55086262.124036
72.97600672.478042
83.40115082.832048
93.82629393.186054
104.251437103.54006
114.676581113.894066
125.101724124.248072
135.526868134.602078
145.952012144.956084
156.377156155.31009
166.802299165.664096
177.227443176.018102
187.652587186.372108
198.077730196.726114
208.502874207.08012
218.928018217.434126
229.353162227.788132
239.778305238.142138
2410.203449248.496144
2510.628593258.85015
2611.053736269.204156
2711.478880279.558162
2811.904024289.912168
2912.3291682910.266174
3012.7543113010.62018
3113.1794553110.974186
3213.6045993211.328192
3314.0297423311.682198
3414.4548863412.036204
3514.8800303512.39021
3615.3051733612.744216
3715.7303173713.098222
3816.1554613813.452228
3916.5806053913.806234
4017.0057484014.16024
4117.4308924114.514246
4217.8560364214.868252
4318.2811794315.222258
4418.7063234415.576264
4519.1314674515.93027
4619.5566114616.284276
4719.9817544716.638282
4820.4068984816.992288
4920.8320424917.346294
5021.2571855017.7003

Miles per gallon (mpg) is a unit of measurement to determine the fuel efficiency of a vehicle. It consists of two parts – miles which represent the distance traveled, and gallon, which represents the unit for the fuel volume in the vehicle. Therefore, miles per gallon details how far a vehicle can travel for every gallon of fuel consumed. The higher the miles per gallon, the more fuel-efficient the vehicle is.

It is a unit of measurement that can be applied to all vehicles, whether that be a car, bus, motorbike, lorry, etc., and is used in countries such as the United States, United Kingdom, and Canada.

There are two variations of miles per gallon – miles per gallon (US) and miles per gallon (UK). This is because the unit of measurement gallon is used in two different systems – the United States customary units and the imperial system. 

As the name suggests, the USgallon is part of the United States customary units system and is used in the United States and other United States territories. The US gallon is the most popular version of the gallon measurement and is, thus, synonymous with the word ‘gallon’. One US gallon equates to 231 cubic inches of liquid.

On the other hand, the UK gallon – also called the Imperial gallon – is used in the United Kindom. The difference between the UK and US gallon is that the UK gallon equates to 277.42 cubic inches of liquid, making it 20% larger than its US counterpart. This explains why a different value must be used when converting from UK gallons.

There’s even a third definition, called the US dry gallon. This is a measurement for dry commodities such as grain and corn. However, it’s rarely used these days.

Kilometers per liter (km/L) is also a unit of measurement that determines the fuel efficiency of a vehicle, i.e., the distance the vehicle can travel for every liter of fuel consumed. Kilometers per liter are used in most European, African, and Asian countries, and the higher the kilometers per liter of a vehicle, the more fuel-efficient it is.

As opposed to miles and gallons, kilometers and liters are metric units that are part of the International System of Units (SI). Kilometers represent the distance traveled, and liters represent the unit for the fuel volume in the vehicle. Therefore, it is simply another way to express the miles per gallon of a vehicle.

As part of the SI, kilometers per liter are standardized worldwide. This means there is no difference between a kilometer-per-gallon measurement in Australia and a kilometer-per-gallon measurement in China – they are equal. As such, we don’t run into the same problem as we do with gallons, where you may have to distinguish between the US and UK versions before converting. 

Converting miles per gallon to kilometers per liter is a straightforward process that can be done in a few steps. The step-by-step method involves converting the miles to kilometers and then the gallons to liters. The first step remains the same – regardless of whether you’re converting from US or UK gallons – however, the value used in the second step will change respectively. 

The second method is the conversation ratio method. Simply memorize the conversion ratio for both US and UK gallons and multiply your mpg value by it to reach your final answer.