Fuel Consumption Converter
Convert between L/100km, km/L, mpg, and mi/gal. Useful for comparing vehicle efficiency across regions.
Fuel Consumption Converter
Enter a fuel economy value and select its unit β all other units update instantly.
Quick References
How to Convert Between MPG, L/100km, and km/L
A rental car in Europe is rated 6.5 L/100km. You want to know if that is better or worse than your 28 mpg sedan at home. Type 6.5, select L/100km, and see that it equals 31.0 UK mpg or 26.2 US mpg. The European car is slightly more efficient than your sedan. The copy button lets you paste the converted value into a spreadsheet or email.
The converter handles 8 units: L/100km, km/L, US mpg, UK mpg, mL/100m, m/mL, mi/US gal, and mi/imp gal. A buyer comparing a Toyota Prius (40.6 US mpg) to a Honda Civic (35.2 US mpg) sees the Prius travels 5.4 more miles per gallon. A fleet manager in Australia converting a truck rated at 45 L/100km to US mpg gets 5.2 mpg, which looks terrible until you remember trucks consume far more fuel than cars. The quick-reference row shows real vehicle benchmarks: Prius at 3.4 L/100km, Civic at 6.2 L/100km, F-150 at 12.4 L/100km.
When the wrong unit makes a huge difference
A car dealer advertises "50 mpg" without specifying US or UK. In US mpg that equals 41.6 UK mpg. In UK mpg that equals 41.7 US mpg. The difference is 20% because a UK (imperial) gallon holds 4.546 litres while a US gallon holds 3.785 litres. A buyer who assumes the wrong standard will overestimate fuel savings by 20%. This converter eliminates that ambiguity by showing both values side by side.
A car rated 5 L/100km does not equal "1/5 = 0.2 mpg." The correct conversion is 47.0 US mpg because you must account for the mile-to-kilometre and gallon-to-litre conversions simultaneously. The formula is US mpg = 235.215 / (L/100km). Entering 5 L/100km gives 47.0 US mpg, not 0.2. This is the single most common fuel economy conversion mistake.
A Tesla Model 3 uses about 15 kWh/100km. To compare with a petrol car, you need to know that 1 litre of petrol contains about 8.9 kWh of energy. Dividing: 15 kWh / 8.9 kWh/L = 1.69 L/100km equivalent. The quick-reference shows Tesla Model 3 at 1.7 L/100km equivalent, which is 4x better than a Prius. This helps buyers compare EVs to petrol cars on equal footing.
Related tools
How the Fuel Consumption Converter Handles MPG and L/100km
All conversions pass through a single base unit: kilometres per litre (km/L). When you enter 30 US mpg, the tool first converts to km/L by multiplying by 2.352145833 (derived from 1 mile = 1.609344 km and 1 US gallon = 3.785411784 L). The result is 70.56 km/L. Then it converts from km/L to each target unit. For L/100km, the formula inverts: 100 / 70.56 = 1.42 L/100km. For UK mpg, it divides by 2.824809703: 70.56 / 2.8248 = 25.0 UK mpg.
Why L/100km and mpg require reciprocal math
L/100km measures volume per distance (how many litres to travel 100 km). US mpg measures distance per volume (how many miles on one gallon). These are inverse relationships. To convert between them, you cannot just multiply by a constant. You must divide by the value. This is why the converter has special handling for L/100km and mL/100m: it detects these units and applies the reciprocal formula instead of a direct multiplication.
The shortcut formula for L/100km to US mpg is: US mpg = 235.215 / (L/100km). This 235.215 constant combines the mile-to-km conversion (1.609344), the gallon-to-L conversion (3.785411784), and the 100-km factor. For UK mpg, the constant is 282.481 instead, because an imperial gallon is 4.54609 L instead of 3.78541 L. The 20% difference between US and UK mpg comes entirely from this gallon size difference.
Quick-reference vehicles and how they compare
The converter shows real vehicle fuel consumption benchmarks below the results. A Toyota Prius at 3.4 L/100km equals 69.2 US mpg. A Honda Civic at 6.2 L/100km equals 37.9 US mpg. A Ford F-150 at 12.4 L/100km equals 19.0 US mpg. The Bugatti Chiron at 22.5 L/100km equals 10.5 US mpg. These references help you understand whether a converted number is reasonable for the vehicle type.
The conversion factors are derived from exact international definitions: 1 mile = 1.609344 km, 1 US gallon = 3.785411784 L, 1 imperial gallon = 4.54609 L. The JavaScript factors are IEEE 754 double-precision approximations providing 15-17 significant digits, which is far more precision than any real-world fuel measurement (typically 1-5% uncertainty depending on driving conditions).
Frequently Asked Questions
How do I convert 7 L/100km to US mpg?
Divide 235.215 by the L/100km value: 235.215 / 7 = 33.6 US mpg. For UK mpg, divide 282.481 by 7 = 40.4 UK mpg. A compact car rated at 7 L/100km is about average for a non-hybrid petrol vehicle. The quick-reference below the results shows this falls between a Honda Civic (6.2 L/100km) and a Toyota Camry (7.4 L/100km).
Why is 50 mpg different in the US and UK?
A US gallon holds 3.785 litres. An imperial (UK) gallon holds 4.546 litres. So 50 US mpg = 60.0 UK mpg. The UK number is always about 20% higher because the gallon is larger. When a car review says '50 mpg' without specifying the standard, ask which gallon they mean. European reviews typically use UK mpg, while American reviews use US mpg.
What is a good fuel economy for a family car?
A petrol Honda Civic achieves about 6.2 L/100km (37.9 US mpg). A diesel version might get 4.8 L/100km (49.0 US mpg). A hybrid Toyota Prius gets 3.4 L/100km (69.2 US mpg). If you drive 15,000 km per year at $1.50/L, the Prius costs $765 per year in fuel while the Civic costs $1,400. The Prius saves $635 annually, which adds up to $6,350 over 10 years.
Can I compare electric cars to petrol cars using this converter?
Yes, with a conversion step. Electric cars use kWh/100km instead of L/100km. One litre of petrol contains about 8.9 kWh of energy. So a Tesla Model 3 using 15 kWh/100km equals about 1.7 L/100km equivalent (15 / 8.9 = 1.69). The quick-reference includes a Tesla Model 3 entry at 1.7 L/100km equivalent, which is 4x more efficient than a Prius.
Why does my car use more fuel in winter?
Cold weather increases fuel consumption by 15-25% for several reasons: the engine takes longer to reach optimal temperature, denser air increases aerodynamic drag, and winter tyres rolling resistance is higher. If your car gets 6 L/100km in summer, expect 7-7.5 L/100km in winter. This converter helps you compare summer and winter ratings by converting between the units your dashboard displays and the units your dealer quoted.
How accurate are manufacturer fuel economy ratings?
Official ratings are measured under lab conditions (NEDC or WLTP cycles) that do not match real driving. Real-world fuel consumption is typically 20-40% worse than the advertised figure. The WLTP standard introduced in 2018 is more realistic than the old NEDC, but still does not account for aggressive driving, heavy loads, or steep hills. Use the converter to translate between units, but expect actual consumption to be higher than any official rating.