Make Sense of MPG, L/100km, and km/L
Car shopping internationally? Or just trying to understand if that rental car in Europe is actually fuel-efficient? Fuel economy ratings can be confusing when every region uses a different system.
The Fuel Efficiency Converter clears up the confusion. Instantly switch between US MPG, UK MPG (yes, they're different!), L/100km, and km/L. Whether you're planning a road trip abroad or comparing specs on a foreign import, get the numbers that make sense to you in seconds.
💡 From my experience: Comparing car efficiency across countries is confusing. MPG (US), MPG (UK), and L/100km are all different. I built this to instantly translate these figures so you can compare vehicles accurately.
Understanding Fuel Efficiency Units
MPG (Miles Per Gallon) - US
Used in: United States
Definition: Number of miles traveled per US gallon of fuel (3.785 liters)
Higher is better: 40 MPG is more efficient than 20 MPG
Typical range: Compact cars: 30-40 MPG, SUVs: 20-28 MPG, Electric/Hybrid: 50+ MPG equivalent
MPG (Miles Per Gallon) - UK/Imperial
Used in: United Kingdom, some Commonwealth countries
Definition: Number of miles traveled per Imperial gallon (4.546 liters, 20% larger than US gallon)
Key difference: UK MPG ratings appear higher than US MPG for the same vehicle due to larger gallon size
km/L (Kilometers Per Liter)
Used in: India, Japan, parts of Asia and Latin America
Definition: Number of kilometers traveled per liter of fuel
Higher is better: 15 km/L is more efficient than 10 km/L
Conversion: ~2.35× MPG (US) = km/L
L/100km (Liters Per 100 Kilometers)
Used in: Europe, Australia, Canada, China, most of the world
Definition: Number of liters consumed to travel 100 kilometers
Lower is better: 5 L/100km is more efficient than 10 L/100km (inverse of other metrics!)
European norm: Small cars: 4-6 L/100km, Mid-size: 6-8 L/100km, SUVs: 8-12 L/100km
📝 Example: Toyota Camry Fuel Economy
Same vehicle, different measurement systems:
- US Rating: 32 MPG (US)
- UK Rating: 38.4 MPG (UK)
- India/Japan: 13.6 km/L
- Europe: 7.35 L/100km
All represent identical fuel efficiency!
Why Convert Fuel Efficiency?
International Car Shopping
Comparing vehicles rated in different countries requires conversion. A European car listing "5.5 L/100km" needs conversion to MPG for American buyers to understand efficiency relative to familiar standards.
Relocating Abroad
Moving to a country with different fuel metrics means learning new efficiency benchmarks. Understanding conversions helps evaluate vehicle purchase or rental options in your new location.
Travel Planning
Renting cars internationally requires estimating fuel costs. Converting local fuel economy ratings to your familiar unit helps budget travel expenses accurately.
Automotive Research
Reading international automotive reviews, comparing global models, or researching import vehicles requires understanding multiple fuel economy standards.
How to Use the Converter
Step 1: Enter Fuel Efficiency Value
Input the fuel economy number from your vehicle specification, manufacturer rating, or real-world measurement.
Step 2: Select Source Unit
Choose the original measurement unit:Step Id: 3587
- MPG (US): If from American source
- MPG (UK): If from British/Commonwealth source
- km/L: If from Asian/Latin American source
- L/100km: If from European/Australian/Canadian source
Step 3: View All Conversions
The calculator instantly displays equivalent values in all four units simultaneously, allowing easy comparison across global standards.
Fuel Economy Tips
Improving Fuel Efficiency
- Maintain proper tire pressure: Underinflated tires reduce MPG by 3-4%
- Reduce speed: Every 5 mph over 50 mph reduces efficiency by ~7%
- Remove excess weight: Every 100 lbs reduces MPG by 1-2%
- Use cruise control: Maintains steady speed, improves highway efficiency
- Avoid idling: Idling gets 0 MPG; turn off engine if stopped >30 seconds
- Regular maintenance: Clean air filters, tune-ups improve efficiency by 4-10%
Calculating Real-World MPG
Method:
- Fill tank completely, note odometer reading
- Drive normally until next fill-up
- Fill tank again, note gallons purchased
- Calculate: (Miles driven) ÷ (Gallons used) = MPG
Repeat over several tanks for accurate average.
Regional Fuel Economy Standards
United States (CAFE Standards)
Current mandate: 49 MPG fleet average by 2026
Testing: EPA tests measure city and highway MPG separately
Labels: Window stickers show combined MPG estimate
European Union
Target: 95g CO2/km by 2021 (~4.1 L/100km gasoline equivalent)
Testing: WLTP (Worldwide Harmonized Light Vehicles Test Procedure)
Focus: CO2 emissions tied to fuel consumption
Japan
Measurement: JC08 mode or WLTC, reported in km/L
Typical vehicles: Kei cars: 20+ km/L, Standard: 15-20 km/L
Hybrids: 25-35 km/L common (Toyota Prius ~30 km/L)
Hybrid & Electric Vehicle Metrics
MPGe (Miles Per Gallon Equivalent)
Used for electric and plug-in hybrid vehicles. Equates electricity consumption to gasoline energy equivalent. Typical EVs: 100-130 MPGe.
Wh/km (Watt-Hours Per Kilometer)
European/global standard for EV efficiency. Measures electricity used per kilometer. Efficient EVs: 150-180 Wh/km.
Frequently Asked Questions
Why is US MPG different from UK MPG?
The US gallon (3.785L) is 20% smaller than the UK Imperial gallon (4.546L). Thus, UK MPG ratings are ~20% higher than US MPG for the same vehicle. Always specify which gallon when comparing MPG.
How do I compare L/100km to MPG?
Remember L/100km is inverse - lower is better, whereas MPG is higher is better. Quick mental conversion: 235.2 ÷ L/100km ≈ MPG (US). Example: 8 L/100km ≈ 29 MPG.
What's considered good fuel economy?
US Standards: 30+ MPG (compact car), 25+ MPG (sedan), 20+ MPG (SUV)
European: <6 L/100km (compact), <7 L/100km (sedan), <8 L/100km (SUV)
Hybrids: 40-60 MPG / 4-5 L/100km
Do manufacturers inflate fuel economy ratings?
Lab test conditions differ from real-world driving. Expect 10-25% lower MPG in actual use due to traffic, weather, driving style, and terrain. EPA updated tests in 2008 to reflect realistic conditions more accurately.
How much fuel costs savings does 5 MPG improvement provide?
Example: 12,000 miles/year, $3.50/gallon gas
25 MPG: 480 gallons = $1,680/year
30 MPG: 400 gallons = $1,400/year
Savings: $280/year or $2,800 over 10 years!
Can I trust the fuel economy displayed on my car's dashboard?
Dashboard trip computers are generally accurate within 5-10% but can optimistically skew. Manually calculate MPG (odometer miles ÷ gallons purchased) for precise measurement.
Why does my actual MPG differ from the EPA rating?
Factors affecting real-world MPG: aggressive driving, excessive idling, cold weather (reduces efficiency 10-30%), use of A/C (reduces ~5-25%), short trips (engine doesn't warm up), roof racks/cargo (adds drag).
Conclusion
Understanding fuel efficiency conversions enables informed vehicle decisions, whether shopping internationally, relocating abroad, or researching automotive options. This converter instantly translates between all major fuel economy standards, helping you compare vehicles across global markets and understand your car's efficiency in any measurement system.
