Fuel Economy Converter
Convert between MPG, L/100km, and km/L with instant results and step-by-step explanations.
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Quick Conversion Reference
Common fuel economy comparisons across different units
| Vehicle Type | US MPG | Imperial MPG | L/100km | km/L |
|---|---|---|---|---|
| Gas Guzzler (Large SUV/Truck) | 15 MPG | 18 MPG | 15.7 L/100km | 6.4 km/L |
| Below Average (Old Car) | 20 MPG | 24 MPG | 11.8 L/100km | 8.5 km/L |
| Average Car (US Fleet) | 25 MPG | 30 MPG | 9.4 L/100km | 10.6 km/L |
| Good Economy Car | 30 MPG | 36 MPG | 7.8 L/100km | 12.8 km/L |
| Efficient Compact Car | 35 MPG | 42 MPG | 6.7 L/100km | 14.9 km/L |
| Excellent Efficiency | 40 MPG | 48 MPG | 5.9 L/100km | 17.0 km/L |
| Hybrid Vehicle | 50 MPG | 60 MPG | 4.7 L/100km | 21.3 km/L |
| Top Hybrid (Toyota Prius) | 55 MPG | 66 MPG | 4.3 L/100km | 23.4 km/L |
| Motorcycle (250cc) | 70 MPG | 84 MPG | 3.4 L/100km | 29.8 km/L |
| Small Motorcycle (125cc) | 100 MPG | 120 MPG | 2.4 L/100km | 42.5 km/L |
💡 Tip: Lower L/100km values and higher MPG/km/L values indicate better fuel efficiency. The highlighted rows show typical efficiency benchmarks.
Master Fuel Economy Conversions with Step-by-Step Math
Learn step-by-step how to convert between different fuel economy units with practical examples from automotive, transportation, and efficiency calculations
1. US MPG to L/100km Conversion
Basic Formula
L/100km = 235.215 ÷ US MPG
Example: 30 MPG → 235.215 ÷ 30 = 7.84 L/100km
For Decimal Users
L/100km = 235.215 ÷ US MPG
Example: 30 MPG → 235.215 ÷ 30.0 = 7.84 L/100km
Key Factor: 235.215 (conversion constant)
This constant comes from: (3.785 L/gallon × 100 km) ÷ 1.609 km/mile
Purpose:
Convert from US efficiency measurement to European/metric consumption standard.
“My car gets 30 MPG. What's that in L/100km?”
Benefits:
Essential for international travel, comparing European vs American car specs, and understanding global fuel efficiency standards.
Steps:
1. Take the constant 235.215
2. Divide by your US MPG value
3. Add L/100km unit to your result
Fraction Method: 30 MPG to L/100km
Step 1: 235.215 ÷ 30 = 7.84
Result: 7.84 L/100km
Decimal Method: 30 MPG to L/100km
Step 1: 235.215 ÷ 30.0 = 7.84
Result: 7.84 L/100km
Result:
30 MPG = 7.84 L/100km (good fuel efficiency)
Example:
“My Honda Civic gets 30 MPG, which equals 7.84 L/100km - that's considered good fuel economy in Europe!”
2. L/100km to US MPG Conversion
Basic Formula
US MPG = 235.215 ÷ L/100km
Example: 8 L/100km → 235.215 ÷ 8 = 29.4 MPG
For Decimal Users
US MPG = 235.215 ÷ L/100km
Example: 8.0 L/100km → 235.215 ÷ 8.0 = 29.4 MPG
Key Factor: Same 235.215 constant (inverse operation)
Lower L/100km values give higher MPG values (inverse relationship)
Purpose:
Convert from European/metric consumption to US efficiency measurement.
“This European car uses 8 L/100km. What's that in MPG?”
Benefits:
Essential for UK/Canadian car shopping, understanding British automotive specs, and comparing efficiency across different English-speaking markets.
Steps:
1. Take the constant 235.215
2. Divide by your L/100km value
3. Add MPG unit to your result
Fraction Method: 8 L/100km to MPG
Step 1: 235.215 ÷ 8 = 29.4
Result: 29.4 MPG
Decimal Method: 8 L/100km to MPG
Step 1: 235.215 ÷ 8.0 = 29.4
Result: 29.4 MPG
Result:
8 L/100km = 29.4 MPG (decent fuel efficiency)
Example:
“The European car spec shows 8 L/100km, which equals 29.4 MPG - that's comparable to many US compact cars.”
3. Imperial vs US MPG Conversions
US to Imperial MPG
Imperial MPG = US MPG × 1.201
Example: 30 US MPG → 30 × 1.201 = 36.0 Imperial MPG
Imperial to US MPG
US MPG = Imperial MPG ÷ 1.201
Example: 36 Imperial MPG → 36 ÷ 1.201 = 30.0 US MPG
Key Factor: 1.201 (gallon size difference)
Imperial gallon (4.546L) is 20% larger than US gallon (3.785L)
Purpose:
Convert between US and UK/Canadian fuel efficiency measurements.
“My UK car gets 40 Imperial MPG. What's that in US MPG?”
Benefits:
Essential for UK/Canadian car shopping, understanding British automotive specs, and comparing efficiency across different English-speaking markets.
Quick Reference:
Imperial MPG is always higher than US MPG for the same vehicle (larger gallon = more miles per gallon)
Example:
“The British car advert says 40 Imperial MPG, which equals 33.3 US MPG - still excellent fuel economy by American standards!”
Tips & Best Practices for Fuel Economy Conversions
Memory Aid: Higher MPG = Lower L/100km (inverse relationship)
More efficient vehicles have high MPG/km/L and low L/100km values
Quick Check: 30 MPG ≈ 8 L/100km ≈ 36 Imperial MPG ≈ 13 km/L
Use this common reference to verify your calculations
Essential Tips:
- • Remember: Lower L/100km = better efficiency
- • Imperial gallons are 20% larger than US gallons
- • City vs highway MPG can vary significantly
- • Consider real-world vs EPA ratings
- • Account for driving conditions and style
Best Practices:
- • Use consistent measurement standards
- • Understand efficiency vs consumption metrics
- • Consider regional differences in gallon sizes
- • Factor in fuel type differences (regular vs premium)
- • Account for vehicle age and maintenance
Real-Life Applications:
- • International car shopping and comparisons
- • Fleet management and cost analysis
- • Environmental impact calculations
- • Travel planning and budget estimation
- • Regulatory compliance and reporting
Watch Out For:
- • Confusing US vs Imperial gallons
- • Mixing efficiency and consumption units
- • Using wrong conversion constants
- • Ignoring real-world vs theoretical ratings
- • Not accounting for different driving cycles
Fuel Economy Conversion Reference
📊 Common Fuel Economy Conversions
| US MPG | Imperial MPG | L/100km | km/L | Efficiency |
|---|---|---|---|---|
| 10 | 12.01 | 23.52 | 4.25 | Poor |
| 15 | 18.01 | 15.68 | 6.38 | Below Average |
| 20 | 24.02 | 11.76 | 8.5 | Average |
| 25 | 30.02 | 9.41 | 10.63 | Good |
| 30 | 36.03 | 7.84 | 12.75 | Very Good |
| 35 | 42.03 | 6.72 | 14.88 | Excellent |
| 40 | 48.04 | 5.88 | 17.01 | Excellent |
| 50 | 60.05 | 4.7 | 21.26 | Excellent |
💡 Note: Efficiency ratings are general guidelines based on L/100km equivalent
📚 Understanding Fuel Economy Units
🇺🇸 US MPG (Miles per US Gallon):
- Most common in the United States
- 1 US gallon = 3.785 liters
- Higher numbers = better efficiency
- Typical car: 20-30 MPG
- Hybrid cars: 40-60 MPG
🇬🇧 Imperial MPG (Miles per Imperial Gallon):
- Used in the UK and some Commonwealth countries
- 1 Imperial gallon = 4.546 liters
- Higher numbers = better efficiency
- Always higher than US MPG for same vehicle
- About 20% higher than US MPG
🌍 L/100km (Liters per 100 kilometers):
- Standard in most countries worldwide
- Shows fuel consumption rate
- Lower numbers = better efficiency
- Typical car: 6-12 L/100km
- More intuitive for consumption-based thinking
⛽ km/L (Kilometers per Liter):
- Common in some Asian countries
- Shows distance per unit of fuel
- Higher numbers = better efficiency
- Directly related to L/100km (km/L = 100 ÷ L/100km)
- Similar concept to MPG but metric
🗺️ Regional Usage of Fuel Economy Units
🇺🇸 United States
- Primary: US MPG
- Official: EPA ratings
- Common: 20-40 MPG range
- CAFE Standards: Fleet averages
🇪🇺 European Union
- Primary: L/100km
- Official: WLTP cycle
- Common: 4-8 L/100km range
- CO₂ Standards: Emissions-based
🇬🇧 United Kingdom
- Primary: Imperial MPG
- Also used: L/100km
- Common: 30-70 MPG range
- Transition: Moving to L/100km
🚗 Typical Fuel Economy by Vehicle Type
Passenger Vehicles (US MPG):
Same Vehicles (L/100km):
💡 Fuel Economy Tips & Facts
Understanding the Numbers:
- US and Imperial gallons are different sizes
- L/100km and km/L are inversely related
- MPG ratings can vary significantly by driving conditions
- Real-world efficiency often differs from official ratings
- Higher speeds typically reduce fuel efficiency
Improving Fuel Economy:
- Maintain steady speeds (avoid rapid acceleration)
- Keep tires properly inflated
- Remove excess weight from vehicle
- Use air conditioning efficiently
- Regular vehicle maintenance
- Plan routes to avoid traffic congestion