Unit Converters

Fuel Efficiency Converter

Convert between MPG (US & UK), L/100km, and km/L instantly. Free online fuel efficiency converter for cars, motorcycles, and all vehicles.

Did this calculator help you?

What is Fuel Efficiency Converter?

A fuel efficiency converter is a free online tool that instantly converts between MPG (US), MPG (UK), L/100km, and km/L. Fuel efficiency is measured differently around the world — the United States uses MPG (US), the United Kingdom uses MPG (UK), most of Europe and Asia use L/100km, and some Asian markets use km/L. This converter lets you compare fuel economy figures from any region in seconds.

Steps:

  1. Enter the fuel efficiency value you want to convert.
  2. Select the source unit (the unit you are converting from).
  3. Select the target unit (the unit you want to convert to).
  4. The converted result appears instantly along with the formula used.
  5. Export the result as PDF, Excel, or CSV if needed.

Formula

Fuel efficiency conversion factors: 1 MPG (US) = 235.214583 / L/100km 1 MPG (UK) = 282.481053 / L/100km 1 L/100km = 235.214583 / MPG (US) 1 km/L = 100 / L/100km 1 MPG (UK) = 1.20095 × MPG (US) 1 MPG (US) = 0.83267 × MPG (UK)

Use Cases

  • Comparing vehicle fuel economy across different countries and regions.
  • Evaluating imported car specifications that use different fuel efficiency units.
  • Understanding fuel consumption figures from manufacturer websites worldwide.
  • Planning fuel costs for international road trips or vehicle purchases.

Key Benefits

  • Convert instantly between MPG (US), MPG (UK), L/100km, and km/L.
  • Compare fuel economy figures from any country or region.
  • Understand fuel consumption ratings from global vehicle manufacturers.

Pro Tips

  • Remember: for MPG and km/L, higher is better. For L/100km, lower is better.
  • When comparing cars across markets, always convert to the same unit first.
  • Check both city and highway fuel efficiency ratings for a complete picture.
  • Real-world fuel efficiency is typically 10–25% lower than official test ratings.

Common Mistakes to Avoid

  • Confusing MPG US with MPG UK — a UK gallon is about 20% larger than a US gallon.
  • Thinking higher L/100km is better — for L/100km, lower numbers mean better efficiency.
  • Mixing up city and highway fuel economy ratings when comparing vehicles.

Key Terms Explained

MPG (US): Miles per US gallon — the standard fuel efficiency unit in the United States
MPG (UK): Miles per Imperial gallon — used in the United Kingdom, where one gallon equals 4.546 liters
L/100km: Liters per 100 kilometers — the standard fuel consumption metric in most of Europe and Asia
km/L: Kilometers per liter — used in some Asian countries as an intuitive measure of distance per fuel unit

Example

Converting 30 MPG US to other units: 30 MPG US = 36.03 MPG UK = 7.84 L/100km = 12.76 km/L. Converting 8 L/100km to other units: 8 L/100km = 29.40 MPG US = 35.31 MPG UK = 12.50 km/L.

Frequently Asked Questions

What is fuel efficiency and how is it measured?
Fuel efficiency measures how far a vehicle can travel on a given amount of fuel. In the US, it is measured in miles per gallon (MPG US). In the UK, it uses Imperial gallons (MPG UK), which are larger. Most of Europe and Asia use liters per 100 kilometers (L/100km), where a lower number means better efficiency. Some Asian markets use kilometers per liter (km/L).
What is the difference between MPG US and MPG UK?
A US gallon is approximately 3.785 liters, while an Imperial (UK) gallon is approximately 4.546 liters — about 20% larger. Because a UK gallon holds more fuel, the same vehicle will show a higher MPG UK number than MPG US. For example, a car that gets 30 MPG US would get about 36 MPG UK.
How do I convert MPG US to L/100km?
Divide 235.214583 by the MPG US value. For example, a car that gets 30 MPG US uses 235.214583 ÷ 30 = 7.84 L/100km. The formula is: L/100km = 235.214583 / MPG US.
How do I convert L/100km to km/L?
Divide 100 by the L/100km value. For example, a car that uses 7.5 L/100km travels 100 ÷ 7.5 = 13.33 km per liter. The formula is: km/L = 100 / L/100km.
Why does a lower L/100km mean better efficiency?
L/100km measures how many liters of fuel are consumed to travel 100 kilometers. A car that uses 5 liters is more efficient than one that uses 10 liters for the same distance. This is why lower numbers are better for L/100km, while higher numbers are better for MPG and km/L.
What is a good fuel efficiency rating?
For modern cars: under 6 L/100km (over 39 MPG US) is excellent, 6–8 L/100km (29–39 MPG US) is good, 8–10 L/100km (24–29 MPG US) is average, and over 10 L/100km (under 24 MPG US) is below average. SUVs and trucks typically consume 10–15 L/100km.
Does fuel efficiency change with speed?
Yes. Most vehicles achieve peak fuel efficiency between 50–80 km/h (30–50 mph). At higher speeds, aerodynamic drag increases significantly, consuming more fuel. City driving with frequent stops also reduces efficiency due to acceleration cycles. Highway driving at moderate speeds typically gives the best fuel economy.
How accurate are manufacturer fuel efficiency ratings?
Official ratings (EPA in the US, WLTP in Europe, JC08 in Japan) are based on standardized test cycles that may not reflect real-world driving. Actual fuel efficiency is typically 10–25% lower than official figures due to driving habits, traffic conditions, weather, vehicle load, and tire pressure.

Discover More Tools

Fresh picks from across our tool library.

Work Calculator

Coin Flip Simulator

Calorie Calculator

Growth Rate Comparison Calculator

Voltage Drop Calculator

Concrete Calculator