Enter your miles driven, gallons used, and gas price to calculate your vehicle's fuel economy (MPG) and trip fuel cost. You can also switch between metric and imperial units to see results in km/L or L/100km. Perfect for checking your car's real-world mileage before or after a road trip.
Fuel Economy (MPG)
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Fuel Economy (km/L)
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Fuel Economy (L/100km)
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Total Trip Fuel Cost
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Cost Per Mile
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Est. Annual Fuel Cost (15,000 mi/yr)
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Gas mileage, measured in miles per gallon (MPG), tells you how far your vehicle can travel on one gallon of fuel. A higher MPG means better fuel efficiency and lower running costs. The EPA tests vehicles under standardized conditions to publish city, highway, and combined MPG ratings.
To calculate MPG, divide the number of miles driven by the number of gallons of fuel used. For example, if you drove 300 miles and used 10 gallons, your MPG is 300 ÷ 10 = 30 MPG. For metric users, divide distance in km by liters used, then multiply by 0.4251 to convert to MPG.
A fuel economy above 30 MPG is generally considered good for a gasoline-powered vehicle. Compact and hybrid cars often achieve 35–50+ MPG, while trucks and SUVs typically fall in the 15–25 MPG range. The best benchmark depends on your vehicle class — compare your MPG to similar vehicles.
It depends on your vehicle's MPG. If your car gets 30 MPG, you'd need 10 gallons for a 300-mile trip (300 ÷ 30 = 10). At a gas price of $3.50/gallon, that trip would cost $35. Use this calculator to estimate fuel needs and cost for any distance.
Several factors influence fuel economy: driving speed (highway driving at 55–65 mph is most efficient), tire pressure, vehicle weight, air conditioning use, engine condition, and driving style (aggressive acceleration and braking hurt MPG). Cold weather, roof racks, and carrying extra cargo also reduce efficiency.
Modern vehicles use an onboard computer that tracks fuel injector pulse width (fuel flow) and wheel speed sensors to estimate real-time and average MPG. The displayed figure is an approximation — for the most accurate reading, use a full tank-to-full tank method and divide miles driven by gallons added.
Most passenger cars have fuel tanks ranging from 12 to 16 gallons, while trucks and SUVs can hold 20 to 36 gallons. A midsize sedan with a 14-gallon tank and 32 MPG rating would have a range of roughly 448 miles on a full tank.
To convert MPG to L/100km, use the formula: L/100km = 235.21 ÷ MPG. For example, 30 MPG converts to 235.21 ÷ 30 ≈ 7.84 L/100km. This calculator displays your fuel economy in MPG, km/L, and L/100km automatically, so no manual conversion is needed.