Fuel Economy Converter
Convert km/L, L/100km, MPG US, and MPG UK with this free fuel economy converter. Compare vehicle fuel efficiency across US, UK, and metric standards.
About This Calculator
The Fuel Economy Converter is a free online tool that instantly converts between four major fuel economy units: kilometers per liter (km/L), liters per 100 kilometers (L/100km), miles per US gallon (MPG US), and miles per UK gallon (MPG UK). Whether you are comparing a car from a different market, planning an international road trip, or simply trying to understand fuel efficiency specifications from different countries, this converter makes it effortless.
How Fuel Economy Conversion Works
Fuel economy measures how efficiently a vehicle uses fuel. Different regions use different measurement systems: the United States uses miles per US gallon (MPG), the United Kingdom and some Commonwealth countries historically used miles per imperial gallon (MPG UK), while most of the world uses liters per 100 kilometers (L/100km). Some markets like India and Japan also use kilometers per liter (km/L).
The conversion relies on precise factors: 1 US gallon equals 3.785 liters, 1 UK (imperial) gallon equals 4.546 liters, and 1 mile equals 1.609 kilometers. Using these constants, the converter accurately transforms any value between all four units. Note that L/100km and MPG are inversely related — a lower L/100km value means better fuel economy, while a higher MPG value means better fuel economy.
Regional Notes
United States: Fuel economy is universally expressed in miles per US gallon (MPG). The EPA provides fuel economy ratings for all new vehicles, and the CAFE standards regulate corporate average fuel economy. US gallons are smaller than UK gallons, so US MPG numbers appear lower than UK MPG for the same vehicle.
United Kingdom: Fuel economy is commonly expressed in miles per imperial gallon (MPG UK) in older vehicles and publications, but new car fuel consumption is increasingly given in L/100km to align with EU standards. The UK gallon is approximately 20% larger than the US gallon.
India and other metric countries: Fuel economy is typically expressed in km/L or L/100km. Indian car manufacturers commonly quote both km/L and L/100km in specifications. The Indian government's fuel efficiency standards are based on km/L measurements.
Frequently Asked Questions
How does the Fuel Economy Converter work?
Enter a fuel economy value and select the source unit (km/L, L/100km, MPG US, or MPG UK) and the target unit. The converter uses standard conversion factors to instantly compute the equivalent value in your desired unit. All four units update simultaneously in the comparison chart.
What is the difference between MPG US and MPG UK?
US and UK gallons are different sizes. A US gallon is 3.785 liters while a UK (imperial) gallon is 4.546 liters, making a UK gallon about 20% larger. This means the same vehicle will show a higher MPG value in UK gallons than in US gallons. For example, 30 MPG US equals approximately 36 MPG UK.
How do I convert US MPG to UK MPG?
To convert US MPG to UK MPG, multiply the US MPG value by 1.201. For example, 25 US MPG × 1.201 = 30.03 UK MPG. This accounts for the difference in gallon sizes between US customary units and imperial units.
How do I convert L/100km to MPG?
To convert L/100km to US MPG, divide 235.21 by your L/100km value. For UK MPG, divide 282.48 by your L/100km value. For example, 8 L/100km = 235.21 ÷ 8 = 29.4 US MPG. Lower L/100km means better fuel economy.
What is a good fuel economy for a car?
A good fuel economy depends on the vehicle type and measurement system. In L/100km, anything under 6 L/100km is excellent, 6-8 L/100km is good, and above 10 L/100km is poor. In US MPG, over 40 MPG is excellent, 30-40 MPG is good, and under 25 MPG is below average. Modern hybrids can achieve over 50 MPG.
How can I improve my vehicle fuel economy?
Drive at steady speeds around 55-65 mph (90-105 km/h), maintain proper tire pressure, remove excess weight, avoid aggressive acceleration and braking, use cruise control on highways, reduce idling time, and keep your vehicle properly maintained with regular oil changes and air filter replacements. Using the recommended grade of motor oil also helps.
How do I manually calculate my car fuel economy?
Fill your tank completely, reset the trip odometer to zero, drive normally for at least 100 miles or several days, then fill the tank again and note the gallons pumped. Divide the miles driven by the gallons used. For example, 300 miles ÷ 10 gallons = 30 MPG. For metric, divide liters used by kilometers driven and multiply by 100 to get L/100km.
Why do different countries use different fuel economy units?
The US uses MPG (miles per gallon) with US gallons as part of its customary measurement system. The UK and some Commonwealth countries historically used MPG with imperial gallons but increasingly use L/100km. Most other countries, including all of Europe, Canada, Australia, and Japan, use L/100km as the standard metric unit. km/L is another metric variant used in some markets like India and Japan.