Office of Transportation and Air Quality

EPA-420-F-11-041

December 2011

Greenhouse Gas Emissions from a 

Typical Passenger Vehicle

The U.S. Environmental Protection Agency (EPA) developed this 

fact sheet to answer common questions about greenhouse gas 

emissions from passenger vehicles. This fact sheet provides emission 

rates and calculations consistent with EPA’s regulatory work.

How much tailpipe carbon dioxide (CO2) is created from burning one gallon 

of fuel?

The amount of CO2 created from burning one gallon of fuel depends on the amount 

of carbon in the fuel. After combustion, a majority of the carbon is emitted as CO2

and very small amounts as hydrocarbons and carbon monoxide. Carbon content 

varies by fuel, and some variation within each type of fuel is normal. The EPA and 

other agencies use the following average carbon content values to estimate CO2

emissions:

CO2

 Emissions from a gallon of gasoline: 8,887 grams CO2 / gallon1

CO2 Emissions from a gallon of diesel: 10,180 grams CO2 / gallon2

Vehicles that use diesel fuel generally have higher fuel economy than comparable 

gasoline vehicles. However, when comparing carbon dioxide emissions, the higher 

CO2 emissions from diesel fuel partially offset the fuel economy benefit.

1 This gasoline factor is from a recent regulation establishing GHG standards for model year 2012-

2016 vehicles (75 FR 25324, May 7, 2010).

2 This diesel factor is from the calculations that vehicle manufacturers use to measure fuel economy 

(40 C.F.R 600.113).

Questions and Answers
2

Questions and Answers

How much tailpipe carbon dioxide (CO2) is emitted from driving a mile?

The average passenger vehicle emits about 423 grams of CO2 per mile. This number can vary 

based on two factors: the fuel economy of the vehicle and the amount of carbon in the vehicle’s 

fuel. The average gasoline vehicle on the road today has a fuel economy of about 21 miles per 

gallon.3 Most vehicles on the road in the US today are gasoline vehicles, and every gallon of 

gasoline creates about 8887 grams of CO2

 when burned. Therefore, the average vehicle when 

driving one mile has tailpipe CO2

 emissions of about:

What are the average annual carbon dioxide (CO2

) emissions of a typical passenger vehicle?

A typical passenger vehicle emits about 5.1 metric tons of carbon dioxide per year. This number 

can vary based on a vehicle’s fuel, fuel economy, and the number of miles driven per year. The 

average gasoline vehicle on the road today has a fuel economy of about 21 miles per gallon and 

drives around 12,000 miles per year. Every gallon of gasoline burned by that vehicle creates 

about 8887 grams of CO2

, and there are one million grams per metric ton. Therefore, the average 

vehicle over a year of driving has tailpipe CO2 emissions of about4:

EPA uses this to compare CO2 emissions from other sources to emissions from passenger vehicles. 

For example, an energy efficiency program that reduces greenhouse gas emissions by 5,100 metric 

tons of CO2

 per year has the same impact as removing 1000 vehicles from the road.

Are there other sources of greenhouse gas emissions from a vehicle?

In addition to carbon dioxide (CO2

), automobiles produce methane (CH4) and nitrous oxide 

(N2

O) from the tailpipe, as well as hydro fluorocarbon (HFC) emissions from leaking air conditioners. The emissions of these gases are small in comparison to CO2

; however, these gases are 

more potent greenhouse gases (they have a higher global warming potential) than CO2

.

3 This is representative of the light duty passenger vehicle fleet as a whole, including both new and existing vehicles. 

EPA expects the average passenger vehicle fuel economy to increase over time as a result of new greenhouse gas 

and fuel economy standards developed in coordination between EPA, DOT and California.

4 This calculation provides a simple way to determine the average annual CO2

 emissions from a passenger vehicle. 

Anyone that needs a more detailed approach should use the EPA’s Motor Vehicle Emission Simulator (MOVES)

model (www.epa.gov/otaq/models/moves/index.htm). This model contains detailed data about the light duty fleet 

and driving patterns in the United States. Although simplified, the calculated annual CO2 emissions above are 

consistent with analyses performed by the EPA using MOVES.

CO2 emissions per mile = 

CO2

 per gallon = 8887 

= 423 grams MPG 21 

Annual CO2 emissions = 

CO2

 per gallon 

x miles = 

8887 

x 12000 = 5.1 metric tons

MPG 21 
3

Questions and Answers

Emissions of greenhouse gases are typically expressed in a common metric so that their impacts 

can be directly compared. The international standard is to express greenhouse gases in units of 

carbon dioxide equivalent, commonly written as CO2e. For a given amount of a greenhouse gas, 

multiplying the amount of gas times the global warming potential (GWP) for that gas results 

in the amount of greenhouse gas in terms of CO2e. For automotive-related gases, these global 

warming potentials are:

Greenhouse Gas Abbreviation GWP5

Carbon Dioxide CO2 1

Methane CH4 25

Nitrous Oxide N2

O 298

Air Conditioning Refrigerant HFC-134a 1,430

It is more difficult to estimate vehicle emissions of CH4, N2O, and HFCs than of CO2. Emissions 

of CH4

 and N2O are dependent on vehicle miles traveled rather than fuel consumption per mile. 

The amount of HFC leakage from air conditioners is dependent on many factors, including 

system design, amount of use, and maintenance. On average, CO2

 emissions represent 95-99% 

of the total greenhouse gas emissions from a passenger vehicle. CH4, N2O, and HFC emissions 

represent roughly 1-5% of the total greenhouse gas emissions from passenger vehicles, after 

accounting for the global warming potential of each greenhouse gas.

What are the tailpipe emissions from a plug-in hybrid or an electric vehicle? What about 

hydrogen fuel cell vehicles?

A vehicle that can only operate on electricity will not emit any tailpipe emissions. A fuel cell 

vehicle operating on hydrogen will emit only water vapor.

Plug-in hybrid vehicles (PHEVs) can operate on either electricity or gasoline. When a PHEV is 

operating on electricity, it does not create any tailpipe emissions. However, when it is operating 

on gasoline, it creates tailpipe greenhouse gas emissions based on the PHEV’s gasoline fuel economy. These emissions can be calculated as shown in the second question. The overall tailpipe 

emissions for a PHEV depend on the percentage of miles the vehicle drives on electricity versus 

gasoline. This can vary significantly based on the PHEV’s battery capacity, how it is driven, and 

how often it is charged. 

Are there any greenhouse gas emissions associated with the use of my vehicle other than 

the tailpipe emissions?

Driving most vehicles creates tailpipe greenhouse gas emissions. Producing and distributing the 

fuel used to power your vehicle also creates greenhouse gasses. Gasoline, for example, requires 

5 These 100-year time horizon GWP values are from the 2007 Intergovernmental Panel on Climate Change 

(IPCC) Fourth Assessment Report.
4

Questions and Answers

extracting oil from the ground, transporting it to a refinery, refining the oil into gasoline, and 

transporting the gasoline to service stations. Each of these steps can produce additional greenhouse gas emissions.

Electric vehicles have no tailpipe emissions; however, greenhouse gas emissions are created during 

both the production and distribution of the electricity used to fuel the vehicle. Calculators on 

Fueleconomy.gov allow you to estimate grams of greenhouse gas emissions per mile for an electric 

vehicle in your region of the country.

I thought my gasoline was blended with ethanol. Does that change the tailpipe CO2 emissions?

It is common in the U.S. to blend gasoline with a small percentage of ethanol. Most of the 

gasoline sold in the U.S.is really a mixture of gasoline and up to 10% ethanol (this mixture is 

often referred to as E10)6. The exact formulation of the gasoline in your vehicle will vary depending on season, region in the U.S., and other factors. While your fuel economy when using 

an ethanol blend in your vehicle will be slightly lower than when using pure gasoline, the CO2

tailpipe emissions per mile will be similar. This is because ethanol has less carbon per gallon 

than gasoline. 

How does the EPA measure CO2 emissions from motor vehicles?

The EPA and automobile manufacturers test vehicles using a set of standardized laboratory 

tests. These tests were designed by the EPA to mimic typical driving patterns. The EPA and the 

Department of Transportation use these values to ensure that the vehicle meets federal corporate 

average fuel economy (CAFE) standards. The test results are then adjusted to reflect different 

driving conditions and estimate fuel economy and greenhouse gas emissions for an average 

driver. These adjusted results are used on the Fuel Economy and Environment Label seen on all 

new vehicles and on Fueleconomy.gov. Detailed information on the test cycles is available on 

the EPA’s National Vehicle and Fuel Emissions Laboratory website (www.epa.gov/nvfel/).

How can I find and compare CO2

 emission rates for specific vehicle models?

You can find and compare vehicle CO2

 emissions at Fueleconomy.gov. Beginning with model 

year 2013, vehicle manufacturers will include tailpipe CO2

 emission rates on the vehicle Fuel 

Economy and Environment labels. These new labels also feature a convenient 1-to 10 Fuel 

Economy and Greenhouse Gas Rating to enable easy comparison shopping. A Smartphone QR 

Code ® on the label will direct consumers to the website Fueleconomy.gov for more information.7

6 The amount of ethanol in gasoline has historically been limited to 10%; however, the E15 waiver increases that 

amount to 15% for some vehicles. For more information see: www.epa.gov/otaq/regs/fuels/additive/e15/

7 QR (or “quick response”) Codes are simply two-dimensional bar codes used to store information. In this case, the 

information is a web site URL. The term QR Code ® is a registered trademark of Denso Wavve Incorporated.
5

Questions and Answers

The EPA publishes additional data in the report “Light-Duty Automotive Technology, 

Carbon Dioxide Emissions, and Fuel Economy Trends” (www.epa.gov/otaq/fetrends.htm). The 

Trends Report analyzes trends in fuel economy and CO2 emissions for new light duty vehicles 

from 1975 to the present.

Where can I find information on the emissions of the transportation sector as a whole? 

How can I compare this to other sectors? 

You can find documents on greenhouse gas emissions on the EPA’s Transportation and Climate 

(www.epa.gov/otaq/climate) website. This website is maintained by the Office of Transportation 

and Air Quality (OTAQ).

•	 U.S. Greenhouse Gas Inventory Report (EPA-430-R-11-005, April 2011):

www.epa.gov/climatechange/emissions/usinventoryreport.html

•	 Light-Duty Greenhouse Gas Standards: www.epa.gov/otaq/climate/regulations.htm

•	 Light-Duty Automotive Technology, Carbon Dioxide Emissions, and

Fuel Economy Trends: www.epa.gov/otaq/fetrends.htm

•	 Fueleconomy.gov

For additional information on calculating emissions of greenhouse gases, please contact: 

OTAQ@epa.gov 

Or you can contact the OTAQ library for document information at:

U. S. Environmental Protection Agency

Office of Transportation and Air Quality

2000 Traverwood Drive

Ann Arbor, MI 48105

734-214-4311 & 734-214-4434

E-mail: Group_AAlibrary@epa.gov