It depends on the vehicle. Modern compact cars average 30–40 MPG, hybrids 45–55+, SUVs and trucks often 18–25. City driving is lower than highway; your real number is usually a bit under the EPA rating.

Gas Mileage Calculator

Q: How do I calculate gas mileage?

Fill the tank, reset the trip odometer, drive, then refill. Divide the miles driven by the gallons it took to refill. 320 miles on 10 gallons is 32 MPG.

Q: How do I convert MPG to L/100km?

Divide 235.2 by the MPG. 32 MPG is 235.2 ÷ 32 = 7.35 L/100km. Note that lower L/100km means better economy, the opposite direction from MPG.

Measure your vehicle's real fuel economy from the miles driven and the fuel it took to refill — in MPG and L/100km.

Fuel economy

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L/100km

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km per litre

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Miles per litre

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The gas mileage formula

MPG = Miles driven ÷ Gallons used
L/100km = 235.2 ÷ MPG

How to measure it accurately

Fill the tank completely and note the odometer (or reset the trip meter). Drive normally. At the next fill-up, record the miles and the gallons it took to fill back up. 320 miles ÷ 10 gallons = 32 MPG (7.35 L/100km). Average a few tanks for a reliable figure.

What affects your real MPG

Your actual economy is usually a bit below the EPA sticker and varies with driving: city stop-and-go is worse than steady highway, aggressive acceleration and high speeds burn more, and under-inflated tires, roof racks, extra weight, and cold weather all cut MPG. Tracking it tank-to-tank is also an early warning system — a sudden drop can flag a mechanical issue. Once you know your MPG, estimate any trip's cost with the fuel cost calculator. Note L/100km runs opposite to MPG: lower is better.

Frequently asked questions

How do I calculate gas mileage?

Miles driven ÷ gallons used. 320 miles on 10 gallons = 32 MPG.

What is a good MPG?

Compacts 30–40, hybrids 45–55+, SUVs/trucks 18–25. City is lower than highway.

How do I convert MPG to L/100km?

235.2 ÷ MPG. 32 MPG = 7.35 L/100km (lower is better).

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Last reviewed: July 2026.