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.

Q: Why does my calculated MPG vary between fill-ups?

Short trips, cold starts, terrain, wind, and exactly how full you top off the tank all affect any single tank's result. Average 3-5 tanks for a reliable figure rather than trusting any one fill-up on its own.

Q: Does premium fuel improve gas mileage?

Only if your engine actually requires it. In a vehicle designed for regular unleaded, using premium gas usually produces no measurable difference in MPG — check the owner's manual for the recommended octane rating before paying extra.

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

Written by the Calculator Index team · Last reviewed September 2026

Fuel economy

—

L/100km

—

km per litre

—

Miles per litre

—

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.

Worked example — metric fill-up

A European driver logs 500 km on 42.5 litres: 42.5 ÷ 500 × 100 = 8.5 L/100km. Converting that to the MPG scale: 235.215 ÷ 8.5 ≈ 27.7 MPG (about 11.76 km per litre).

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.

Typical MPG by vehicle class

Vehicle type	Typical combined MPG
Subcompact / compact car	32–40
Midsize sedan	28–36
Hybrid sedan	50–60
Small SUV / crossover	26–32
Large SUV	18–24
Pickup truck	17–22

Common gas mileage measurement mistakes

Topping off inconsistently. Not filling to the same "click" point at both ends of the measurement can introduce a gallon or more of error, especially across pumps with different auto-shutoff sensitivity.
Forgetting to reset the trip odometer. Using a running trip total instead of the true fill-to-fill distance compounds error into every later calculation.
Comparing your tank-to-tank MPG directly against the EPA sticker. The EPA rating comes from a specific lab test cycle that differs from real-world driving, so some gap between the two numbers is normal, not a sign of a problem.

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).

Why does my calculated MPG vary between fill-ups?

Short trips, cold starts, terrain, wind, and how full you top off all affect a single tank. Average 3-5 tanks for a reliable number.

Does premium fuel improve gas mileage?

Only if your engine requires it — otherwise premium in a regular-unleaded car usually makes no measurable difference.

Related calculators

Last reviewed: September 2026.