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⛽ Fuel Economy Calculator
Calculate MPG, L/100km, and fuel efficiency
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Fuel Economy
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MPG (US)
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L/100km
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km/L
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MPG (UK)
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Fuel Economy Comparison
📚 Understanding Fuel Economy
What is Fuel Economy?
Fuel economy measures how efficiently a vehicle uses fuel. It's typically expressed as miles per gallon (MPG) in the US, liters per 100 kilometers (L/100km) in Europe, or kilometers per liter (km/L) in Asia. Higher MPG or km/L values indicate better fuel efficiency, while lower L/100km values indicate better efficiency.
How to Calculate Fuel Economy
The basic formula for calculating fuel economy is:
- MPG = Distance (miles) ÷ Fuel Used (gallons)
- L/100km = (Fuel Used (liters) ÷ Distance (km)) × 100
- km/L = Distance (km) ÷ Fuel Used (liters)
Fuel Economy Categories
- Excellent (40+ MPG): Hybrids, electric vehicles, small efficient cars
- Good (30-40 MPG): Compact cars, efficient sedans
- Average (25-30 MPG): Midsize sedans, small SUVs
- Below Average (20-25 MPG): Large sedans, SUVs, light trucks
- Poor (under 20 MPG): Large SUVs, trucks, performance vehicles
Factors Affecting Fuel Economy
- Driving habits: Aggressive acceleration and braking reduce efficiency by 15-30%
- Speed: Fuel economy decreases rapidly above 50 mph
- Vehicle maintenance: Dirty air filters can reduce MPG by up to 10%
- Tire pressure: Under-inflated tires reduce fuel economy by 0.2% per PSI drop
- Weight: Extra 100 lbs can reduce MPG by 1-2%
- Aerodynamics: Roof racks and open windows increase drag
- Weather: Cold weather and AC use reduce fuel economy
- Terrain: Hills and mountains significantly impact efficiency
Tips to Improve Fuel Economy
- Drive smoothly: Avoid rapid acceleration and hard braking
- Maintain steady speed: Use cruise control on highways
- Reduce speed: Driving 55 mph instead of 65 mph can improve MPG by 15%
- Keep tires inflated: Check pressure monthly
- Remove excess weight: Clean out your trunk and remove roof racks
- Regular maintenance: Change oil, air filters, and spark plugs as recommended
- Plan trips: Combine errands to reduce cold starts
- Minimize idling: Turn off engine if stopped for more than 30 seconds
Converting Between Units
- MPG to L/100km: L/100km = 235.214 ÷ MPG
- L/100km to MPG: MPG = 235.214 ÷ L/100km
- MPG to km/L: km/L = MPG × 0.425144
- km/L to MPG: MPG = km/L × 2.35214
Frequently Asked Questions
What is considered good fuel economy?
For gasoline vehicles, 30+ MPG is considered good, 40+ MPG is excellent. For context, the average new car in the US gets about 25 MPG. Hybrids typically achieve 40-60 MPG, while electric vehicles have equivalent ratings of 100+ MPGe. Fuel economy varies significantly by vehicle type and driving conditions.
How do I accurately measure my fuel economy?
Fill your tank completely, reset your trip odometer, and drive normally. At your next fill-up, note the miles driven and gallons added. Divide miles by gallons for MPG. For best accuracy, track over multiple fill-ups and average the results. Avoid topping off the tank, as this can skew measurements.
Why is my actual MPG lower than the EPA rating?
EPA ratings are based on standardized tests that may not reflect real-world driving. Factors like aggressive driving, short trips, cold weather, AC use, traffic, and terrain all reduce fuel economy. City driving typically gets 20-40% lower MPG than highway driving. Your actual MPG may vary by 10-30% from EPA estimates.
Does driving faster really use more gas?
Yes, significantly. Fuel economy peaks around 50 mph for most vehicles and decreases rapidly at higher speeds due to increased aerodynamic drag. Driving 70 mph instead of 55 mph can reduce fuel economy by 15-25%. Each 5 mph over 50 mph is equivalent to paying an extra $0.20 per gallon.
How much can proper tire pressure improve MPG?
Properly inflated tires can improve fuel economy by up to 3%. Under-inflated tires increase rolling resistance, reducing MPG by about 0.2% for every 1 PSI drop in pressure. Check tire pressure monthly when tires are cold. The recommended pressure is on a sticker inside the driver's door, not on the tire sidewall.
What's the difference between city and highway MPG?
Highway MPG is typically 20-40% higher than city MPG because highway driving involves steady speeds with minimal braking and acceleration. City driving requires frequent stops and starts, which consume more fuel. The EPA combined rating is 55% city and 45% highway driving. Your actual mix may differ based on your commute.
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