Calculate your vehicle's fuel economy in MPG, cost per mile, and trip fuel costs with comparison charts and efficiency tips.
The Fuel Mileage Calculator helps you determine your vehicle's fuel economy, cost per mile, and total fuel expenses for any trip. Enter the distance traveled and fuel used to get an MPG reading, or enter a planned trip distance and estimated MPG to estimate fuel cost before you drive.
Fuel economy is one of the easiest vehicle metrics to track over time. It helps you budget for commuting and road trips, compare vehicles, and notice changes that may point to maintenance issues like low tire pressure, worn filters, or engine problems.
The calculator supports both US MPG and metric L/100km formats, so you can work with the unit that matches your vehicle or trip records.
Use this calculator to turn odometer, fuel, and price numbers into trip cost and efficiency data. It is useful for comparing vehicles, tracking mileage changes after maintenance, and estimating how much a commute or road trip will cost.
MPG = Distance (miles) / Fuel (gallons). Cost Per Mile = Fuel Price / MPG. Trip Cost = (Trip Distance / MPG) × Price Per Gallon. L/100km = (Liters / km) × 100.
Result: 28.0 MPG, $0.125/mile
350 miles ÷ 12.5 gallons = 28.0 MPG. At $3.50/gallon, that's $0.125 per mile or $43.75 for the full tank.
MPG (Miles Per Gallon) is the standard US fuel economy measure. Higher is better. L/100km (Liters per 100 Kilometers) is the metric equivalent — lower is better. The relationship is inverse: 30 MPG ≈ 7.84 L/100km. Some countries also use km/L, where higher is better like MPG.
Vehicle design (weight, aerodynamics, engine type) determines base efficiency. Driving behavior adds 20-30% variation: aggressive driving, speeding, excessive idling, and short trips all reduce MPG. Environmental factors include temperature (cold starts use more fuel), altitude, and wind. Maintenance factors include tire pressure, oil viscosity, air filter condition, and engine tune.
The biggest savings come from driving behavior, not fuel shopping. Maintaining 60 mph instead of 75 mph saves roughly 15% on fuel. Combining short trips saves cold-start fuel waste. Properly inflating tires saves 3-5%. Using the recommended oil grade saves 1-2%. Over 15,000 miles per year at $3.50/gallon, improving from 25 to 30 MPG saves $350 annually.
Last updated:
Fill the tank completely, reset the trip odometer, drive normally, then fill up again. Divide miles driven by gallons added. Repeating the process over several tanks gives a steadier average.
The US fleet average is about 25 MPG. Compact cars get 30-40 MPG, hybrids 40-60 MPG, and trucks/SUVs 18-25 MPG. Check EPA ratings for your specific model.
L/100km = 235.215 / MPG. For example, 30 MPG ≈ 7.84 L/100km.
EPA tests are lab-based. Real-world conditions like speed, idling, cold weather, AC use, and driving style often reduce MPG compared with test figures.
Yes, significantly. Most vehicles are most efficient at 45-65 mph. Above 65, fuel economy drops roughly 7% for each 5 mph increase.
Running AC typically reduces fuel economy by 5-15% in city driving. At highway speeds, AC is more efficient than opening windows (which creates drag).