Fuel Economy Converter

Convert fuel economy between MPG, km/L, and L/100km instantly. Enter any value to compare your car's fuel efficiency across US, imperial, and metric units with this free fuel economy converter.

How to Use

  1. Enter the fuel economy value

    Type the fuel economy value you want to convert.

  2. Select the units

    Choose the source unit (e.g., MPG) and the target unit (e.g., km/L).

  3. View the result

    Click Convert to see the converted fuel economy value.

What is fuel economy?

Fuel economy is an efficiency metric that shows how far a vehicle can travel on one unit of fuel. The farther you go on less fuel, the better the economy, which means lower running costs and fewer emissions.

Different notations by country

Korea and Japan use km/L, the United States uses MPG (miles per gallon), and most of Europe uses L/100km. For km/L and MPG, higher is better, but L/100km works the opposite way, lower is better, which can easily cause confusion.

  • Comparing an imported car's MPG against the local km/L
  • Converting a European vehicle's L/100km into km/L

Calculation formula

Every unit is first converted to the base value km/L, then to the target unit.

result = value × (source factor) ÷ (target factor)

The factors are US MPG = 0.425144, UK MPG = 0.354006, and km/L = 1. Example: 30 mpg (US) → 30 × 0.425144 ≈ 12.75 km/L.

L/100km has a reciprocal relationship, so it is handled separately as km/L = 100 ÷ (L/100km). Example: 8 L/100km → 100 ÷ 8 = 12.5 km/L.

Frequently Asked Questions

What is fuel economy?
Fuel economy is a metric that shows how far a vehicle can travel on one unit of fuel. It is expressed in various units such as km/L, MPG, and L/100km, and except for L/100km, a higher value means better fuel efficiency.
What is the difference between km/L and MPG?
km/L is the distance in kilometers traveled per liter of fuel, used in Korea and Europe, while MPG (miles per gallon) is the miles traveled per gallon, used in the US and UK. 1 mpg (US) ≈ 0.425 km/L.
How do I interpret L/100km?
L/100km is the amount of fuel in liters needed to travel 100 km. Unlike other units, a smaller number means better fuel economy. It is mainly used in Europe.
How do I convert L/100km to km/L?
L/100km and km/L have a reciprocal relationship, calculated as km/L = 100 ÷ (L/100km). For example, 10 L/100km is 100 ÷ 10 = 10 km/L. Converting from km/L back to L/100km uses the same formula.
Are US gallons and UK gallons different?
Yes, a US gallon is about 3.785 L while a UK (Imperial) gallon is about 4.546 L. Because the same MPG value means better economy under the UK standard, you must always check which gallon is being used when comparing.
What exact factors are used for fuel economy conversion?
Using km/L as the base, this converter uses the factors 1 mpg (US) = 0.425144 km/L and 1 mpg (UK) = 0.354006 km/L. These are derived from the definitions 1 mile = 1.609344 km and 1 US gallon = 3.78541 L.
What is 30 MPG in km/L?
30 mpg (US) is 30 × 0.425144 ≈ 12.75 km/L. 30 mpg (UK) is 30 × 0.354006 ≈ 10.62 km/L, so the same number gives different results due to the gallon difference.
Does better fuel economy always mean lower cost?
Usually, but you also need to consider fuel type and price. Diesel may have high km/L but a different fuel price, while EVs are compared by efficiency (km/kWh) instead of fuel economy. Real-world economy also depends heavily on driving habits, traffic, and outside temperature.
2026 international standards

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