What Is Mpg?

Learn how a car's miles per gallon (mpg) is determined and how to know if it gets good gas mileage.
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Written by Shannon Bradley
Lead Writer
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Edited by Funto Omojola
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Miles per gallon (mpg) is the number of miles a car can travel on a single gallon of fuel. So, if a vehicle goes 30 miles on a gallon of gas, it would have an mpg of 30.

A car’s mpg varies based on many factors, like your driving habits, level of traffic, road conditions and type of fuel you’re using. For this reason, a vehicle’s mpg is usually calculated as an average over a period of time as opposed to one fixed number.

The higher a vehicle’s average mpg, the farther you can drive using less fuel, thus reducing fuel expenses.

How is a car’s mpg determined?

The U.S. Environmental Protection Agency (EPA) calculates average mpg for specific makes and models of vehicles based on the auto manufacturer’s self-reporting and the EPA’s own testing.

The EPA provides three different types of mpg measurements for every vehicle type:

  • City mpg: for driving at lower speeds with more stopping and accelerating, which uses more gas.

  • Highway mpg: for driving at higher speeds on a longer stretch of road without a lot of stopping and starting.

  • Combined mpg: for the average of city and highway mpg.

All three measurements are part of a vehicle’s fuel economy rating. A new vehicle’s mpg and fuel economy information is federally mandated to appear on the window sticker of all new cars and certain trucks. You can also find mpg and fuel economy ratings for specific vehicles on manufacturer websites, online car retailer sites and fueleconomy.gov.

If you’re trying to determine the average mpg of a car you already own, you can do that in several ways.

One way is to calculate your mpg manually. The next time you fill your gas tank, make a note of your odometer reading, then drive your car like you normally would until your tank is almost empty. When you refill your tank, note the new odometer reading along with how many gallons of gas it took. Subtract the first odometer reading from the second one to determine the number of miles you went between gas fill-ups. Divide that figure by how many gallons of gas it took to fill your car the second time. This will give you your mpg. Do this several times to calculate your average mpg since your driving may fluctuate between fill-ups.

You can also use online calculators, like NerdWallet’s Gas Mileage Calculator and Comparison tool. If you drive a newer car, it will most likely have an mpg display somewhere on the dashboard.

Why do some cars have an MPGe?

With the growing availability and use of electric vehicles, MPGe was developed by the EPA to measure and compare an electric vehicle’s energy consumption level to a gas-powered vehicle’s fuel consumption, or mpg. According to the formula, using 33.7 kWh of power is equivalent to using 1 gallon of gas. So, an electric vehicle that travels 100 miles on 33.7 kWh would have a 100 MPGe rating.

Did you know...

Mpg is a measurement used in the U.S., but you’re less likely to see it in other countries. For example, European countries use liters per 100 kilometers, or l/100km, to measure fuel efficiency. To convert l/100km to mpg, divide 282.5 by the car's l/100km number.

What is good gas mileage?

A “good mpg” varies by vehicle class. The EPA publishes annual lists of the most fuel efficient vehicles by class — with one list including electric vehicles and the other excluding them.

To give you an idea of what's a good mpg, here’s the combined mpg from the EPA’s most fuel efficient vehicles list (excluding EVs) for 2024. Note that the mpg shown for subcompacts, compacts, midsize and large classes are for standard hybrid vehicles.

  • Subcompacts: 32 combined mpg.

  • Compacts: 50 combined mpg.

  • Midsize: 57 combined mpg. 

  • Large: 48 combined mpg.

  • Small SUV: 53 combined mpg.

  • Standard SUV: 36 mpg.

  • Small Pickup Trucks: 37 mpg.

  • Standard Pickup Trucks: 26 mpg.

  • Minivans: 36 mpg.

Why is it helpful to know a car’s mpg?

Knowing a vehicle’s average mpg can be beneficial in many ways. If you’re shopping for a new car, you can compare the mpg of various cars to determine which one will consume less fuel and save you money. If you know the average mpg for your current car, a sudden decline could be an indicator of a mechanical issue that needs to be addressed. Also, if you’re environmentally conscious, driving a car with a higher mpg can help to reduce vehicle pollution.