Fuel Mileage Calculator

To calculate MPG, note your odometer reading when you fill up the tank. Drive normally, then fill up again and note the new odometer reading and the amount of fuel added. Subtract the first reading from the second to get miles driven, then divide that number by the gallons of fuel used. The formula is: MPG = Miles Driven ÷ Gallons Used.

A US gallon equals approximately 3.785 liters, while an Imperial (UK) gallon equals approximately 4.546 liters. This means Imperial MPG figures are always higher than US MPG for the same vehicle — roughly 20% higher. Always check which gallon standard is being used when comparing fuel economy figures.

To convert US MPG to liters per 100 km, use the formula: L/100km = 235.21 ÷ MPG (US). For example, a car getting 30 MPG US achieves approximately 7.84 L/100km. Lower L/100km values indicate better fuel efficiency, while higher MPG values also indicate better efficiency.

Key ways to improve fuel mileage include maintaining correct tire pressure, avoiding aggressive acceleration and hard braking, removing excess weight from the vehicle, keeping up with regular maintenance (clean air filters, fresh spark plugs), and reducing highway speeds. Driving at 55 mph instead of 75 mph can improve fuel economy by up to 20%.

Fuel efficiency is affected by vehicle type and size, engine displacement, drivetrain (FWD/RWD/AWD), tire condition and pressure, driving style, road conditions, weather, use of air conditioning, and vehicle load. Four-wheel drive systems generally consume more fuel than two-wheel drive because the engine must power additional components.

Both methods give accurate results. Using odometer readings is convenient if you didn't reset your trip counter — just record the reading before and after a full tank. Using trip distance is easier if your vehicle has a trip odometer you reset at each fill-up. The key is to measure a full tank-to-tank cycle for the most accurate result.

According to the American Automobile Association (AAA), the average American driver spends about $3,000 per year on gasoline. This varies significantly based on how many miles you drive, your vehicle's fuel efficiency, and local gas prices. Improving your MPG by even a few points can save hundreds of dollars annually.

For a gasoline-powered car, 30 MPG or above is considered good fuel economy. Compact and midsize sedans typically achieve 28–40 MPG combined, while SUVs and trucks range from 18–28 MPG. Hybrid vehicles can exceed 50 MPG combined. You can compare official EPA ratings at fueleconomy.gov to benchmark your vehicle's real-world performance.