Fuel Economy Converter

About the Fuel Economy Converter

Fuel economy is reported in three different ways around the world, and two of them are mirror images of each other. The United States uses miles per gallon, so a bigger number is better. Canada, most of Europe and Australia use liters per 100 kilometers, where a smaller number is better. Parts of Asia and some used-car markets quote kilometers per liter. This converter translates between those three, so a window sticker, an import listing or a spec sheet can be understood without a table.

Because L/100 km measures fuel used per distance while MPG and km/L measure distance per fuel, the relationship is a reciprocal and not a simple multiple. The tool first converts your figure to kilometers per liter, using 1.609344 kilometers per mile and 3.78541 liters per US gallon, and then converts that value to the unit you picked. The mile and gallon in the tool are the US ones. Output is rounded to at most six decimal places, and an input of zero or less is rejected with a message.

The page helps car buyers comparing imports, travelers working out costs for a rental abroad, drivers who want to translate a trip computer reading, fleet managers working with mixed sources, and students studying unit conversion. A converted rating is a label number, not a promise. Real consumption depends on driving style, load, weather, tires, speed and the test procedure behind the rating, which differs from region to region.

When to Use It

How to Use It, Step by Step

1. Get a fuel-economy figure and note its unit. Window stickers and US reviews use MPG, European spec sheets and Canadian ads use L/100 km, and some used-car sites and logbooks use km/L.
2. Type the number into the Value field. It accepts values above zero and up to one million, with decimals allowed, so you can enter 28 or 5.4.
3. Pick your starting unit in the From list: MPG (US), L/100 km or km/L. The tool opens on MPG (US).
4. Pick the unit you want in the To list. It opens on L/100 km; choose MPG (US) or km/L if you need either of those.
5. Press the Convert Fuel Economy button. The summary line restates your figure and the result, and a highlighted In box shows the converted value with its unit label.
6. Read the note under the result. It reminds you that the MPG here is US miles per US gallon, and that a lower L/100 km and a higher MPG or km/L both mean better efficiency.
7. Check the direction of your comparison. If you convert two cars, make sure you read each in the same unit and remember that, for L/100 km, the car with the smaller number uses less fuel.
8. If you see the message asking for a value greater than zero, check for an empty field or a zero, since none of the three units can be zero in practice.

Understanding Your Results

The result is the same efficiency expressed in a different unit. It is not a better or worse number; a car rated 28 MPG and 8.4 L/100 km is a single car. The summary line shows the two forms next to each other with up to six decimals, which is more than any rating supports. A real-world figure rounded to one decimal for L/100 km or to a whole number for MPG is adequate.

A quick check is to use the constant 235.215. Dividing it by MPG gives L/100 km, and dividing it by L/100 km gives MPG. For 28 MPG that is 235.215 divided by 28, or about 8.4. A km/L value is 100 divided by the L/100 km figure, and 15 km/L is 6.67 L/100 km. If your answer breaks these relationships, the From and To lists are probably reversed.

When comparing vehicles, think in fuel used rather than miles per gallon. A change from 15 to 20 MPG saves far more fuel over a year than a change from 40 to 45, even though both are 5 MPG improvements. Use L/100 km to see the true gain, then multiply by your annual distance to estimate fuel volumes and costs at your local price.

More Worked Examples

Tips for Better Results

• Memorize 235.2 as the bridge number. Dividing it by a US MPG rating gives liters per 100 kilometers, and dividing it by a L/100 km rating gives US MPG, a handy check without any calculator.
• To estimate fuel for a trip in metric terms, multiply the distance in kilometers by the L/100 km figure and divide by 100. A 650 kilometer drive at 6.5 L/100 km needs about 42 liters.
• To estimate the range of a tank in miles, multiply the tank size in gallons by the MPG. A 14 gallon tank at 28 MPG covers about 392 miles, although keeping a reserve is wise.
• When averaging two fill-ups of the same distance, average the L/100 km values, not the MPG values. Averaging MPG overstates efficiency because lower consumption weighs more heavily in the distance-per-fuel figure.
• Be careful comparing ratings from different regions. Test procedures differ, so a car's label in the US and its label in Europe rarely match exactly even after conversion, and real driving usually differs from both.
• Track your own fill-ups for a few tanks. Divide the distance by the fuel added at each fill, then convert with this tool, to see how your car compares to the label under your own driving conditions.

Common Mistakes to Avoid

• Reading a bigger number as better in every unit. For MPG and km/L it is, but for L/100 km a smaller number is better, so a car rated 5 L/100 km is more efficient than one rated 8.
• Using imperial MPG figures with the US option. A UK rating of 40 mpg corresponds to about 33 US MPG, so a UK source entered as US MPG makes a car look far more efficient than it is.
• Averaging MPG over equal distances. A car that gets 20 MPG on one trip and 40 on another of the same distance averages about 26.7 MPG, not 30, so convert to L/100 km, average there, and convert back.
• Expecting equal MPG gains to save equal fuel. Going from 15 to 20 MPG saves much more fuel per distance than 40 to 45, so judge upgrades by liters per 100 kilometers.
• Treating a converted label rating as a forecast. Speed, load, hills, cold weather and short trips all lower real economy, so budget with your own recorded numbers when they are available.

Assumptions and Limits

• The tool uses 1.609344 kilometers per mile and 3.78541 liters per US gallon, and treats L/100 km as 100 divided by km/L. All three units are converted through km/L, so the results are consistent in every direction.
• MPG means US miles per US gallon. UK imperial MPG is about 20 percent higher for the same car, and it is not an option in this tool.
• Results are rounded to at most six decimal places. The precision is a side effect of exact formulas and does not mean fuel economy can be measured that accurately in the real world.
• Ratings from official tests are useful for comparison but do not predict your own consumption. For fuel budgets, emissions reporting or fleet contracts, use measured data from your vehicles and the method required by the relevant authority.

Key Terms

MPG (US)

Miles traveled per US gallon of fuel. Higher means better efficiency, and it uses the US gallon of 3.78541 liters.

L/100 km

Liters of fuel used to travel 100 kilometers. Lower means better efficiency, and it is the standard unit in much of the world.

km/L

Kilometers traveled per liter of fuel. It is the metric counterpart of MPG, and the intermediate unit this converter uses.

Reciprocal

The result of dividing 1 by a number. L/100 km is proportional to the reciprocal of km/L, which is why conversions do not use a single multiplier.

Imperial gallon

The UK gallon of about 4.546 liters, around 20 percent larger than the US gallon. It makes UK MPG figures look higher.

Test cycle

A standardized driving pattern used in labs to rate fuel economy. Different regions use different cycles, so ratings are not directly interchangeable.