Key numbers
- Electricity: 0.350 kg CO2 per kWh (eGRID2023 US average, 771.5 lb/MWh)
- Natural gas: 5.306 kg CO2 per therm (53.06 kg/MMBtu)
- Gasoline: 8.78 kg CO2 per gallon
- Flights: 0.207 / 0.129 / 0.163 kg CO2 per passenger-mile (short / medium / long haul)
On this page
How to use the Carbon Footprint Calculator
- 1Enter your numbersFill in electricity use (kWh/month), natural gas use (therms/month), miles driven (mi/yr), fuel economy (mpg), short-haul flights (<300 mi) (mi/yr), medium-haul flights (300–2,300 mi) (mi/yr), long-haul flights (>2,300 mi) (mi/yr), people in household and grid emission factor (kg CO2/kWh). Every field starts with a typical value you can overwrite.
- 2Check the assumptionsCO2 only; EPA GHG Emission Factors Hub 2025 / eGRID2023.
- 3Read the resultsThe calculator shows total co2 per year, per person, electricity, natural gas, driving and flights, and updates as you type.
- 4Use the resultCompare it with your bill, a quote or a product spec sheet before you buy or install anything.
Results update as you type. Back to the calculator ↑
This carbon footprint calculator estimates the carbon dioxide (CO2) your household emits each year from the four things most homes can read off a bill or an odometer: electricity, natural gas, driving and flying. Enter your monthly kWh and therms, the miles you drive and your car’s mpg, and your flight miles by distance band. You get your total in tonnes of CO2 per year, the figure per person and the share from each source. Every emission factor comes from the U.S. Environmental Protection Agency (EPA), and you can swap the grid factor for your own region.
How the carbon footprint calculator works
A carbon footprint is activity × emission factor, summed over everything you do:
- Electricity: kWh per month × 12 × grid factor (kg CO2/kWh)
- Natural gas: therms per month × 12 × 5.306 kg CO2/therm
- Driving: miles per year ÷ mpg × 8.78 kg CO2/gallon
- Flights: passenger-miles in each band × that band’s factor
- Per person: total ÷ household size
Your kWh and therms are printed on your utility bills. If you only know your electric bill in dollars, convert it with the electricity usage calculator first.
Emission factors used
| Source | Factor | Data |
|---|---|---|
| Grid electricity (US average) | 0.350 kg CO2/kWh | EPA Hub 2025, Table 6 (eGRID2023), 771.5 lb/MWh total output |
| Natural gas | 5.306 kg CO2/therm | EPA Hub 2025, Table 1, 53.06 kg/MMBtu |
| Motor gasoline | 8.78 kg CO2/gallon | EPA Hub 2025, Table 2 |
| Flight, short haul (under 300 mi) | 0.207 kg CO2/passenger-mile | EPA Hub 2025, Table 10 |
| Flight, medium haul (300 to 2,300 mi) | 0.129 kg CO2/passenger-mile | EPA Hub 2025 |
| Flight, long haul (2,300 mi or more) | 0.163 kg CO2/passenger-mile | EPA Hub 2025 |
The grid factor converts as 771.5 lb × 0.4536 kg/lb ÷ 1,000 kWh = 0.350 kg per kWh. The therm factor follows from 1 therm = 0.1 MMBtu. EPA data is a U.S. Government work in the public domain; we note the edition so the numbers can be updated when the EPA publishes new ones.
Worked example
The default inputs show the calculation for a two-person household:
- Electricity: 855 kWh × 12 × 0.350 = 3,590 kg
- Natural gas: 40 therms × 12 × 5.306 = 2,547 kg
- Driving: 12,000 mi ÷ 28 mpg = 428.6 gallons × 8.78 = 3,763 kg
- Flights: 2,000 medium-haul miles × 0.129 = 258 kg
- Total: 10,158 kg = 10.2 tonnes of CO2 a year, or 5.1 tonnes per person
Driving and electricity are the two biggest slices in this example, which is why an electric car or rooftop solar can make such a difference.
Why your grid factor matters
The 0.350 kg figure is a national average. Your local grid may burn more coal, or use more hydro, nuclear, wind and solar, and eGRID publishes a separate rate for each of its subregions (EPA eGRID summary data). Replace the grid factor with your subregion’s total output rate (lb/MWh × 0.4536 ÷ 1,000) for a local answer. Electricity your own solar panels produce does not come from the grid, so leave it out of the kWh you enter.
Driving: gasoline vs electric
For context, the EPA’s equivalencies page uses an average of 10,917 miles a year and 22.8 mpg for passenger vehicles (EPA). An EV’s driving emissions show up on your electricity bill instead: estimate its kWh with the EV charging cost calculator and add them to your monthly kWh.
How to reduce your carbon footprint
- Use fewer kWh. Find the biggest loads with the electricity cost calculator.
- Clean up the kWh you use. Rooftop solar or a renewable tariff lowers the emissions behind each kWh.
- Heat with electricity. A heat pump replaces therms of gas with kWh, which get cleaner as the grid does.
- Drive less or go electric. Each gallon saved is 8.78 kg of CO2.
- Fly less. Short flights have the highest factor per mile.
To understand the unit behind most of these numbers, read what is a kilowatt-hour.
History of carbon footprint factors
The EPA’s GHG Emission Factors Hub is published by its Center for Corporate Climate Leadership to give organisations a regularly updated set of default factors for greenhouse gas inventories, with editions archived on the same page back to 2011. Its electricity factors come from eGRID, the EPA’s database of emissions from US power plants; the 2025 Hub, released in January 2025 and the current edition, uses eGRID2023 data. Aviation has been studied separately because aircraft affect the climate through more than CO2. Lee et al. (2021) found that non-CO2 effects, mainly contrail cirrus, make up a large part of aviation’s net effective radiative forcing, which is why this calculator says its flight numbers are CO2 only.
References
- U.S. EPA (2025). GHG Emission Factors Hub. epa.gov
- U.S. EPA (2025). GHG Emission Factors Hub 2025 (PDF). epa.gov
- U.S. EPA. eGRID Summary Data. epa.gov
- U.S. EPA. Greenhouse Gas Equivalencies Calculator: Calculations and References. epa.gov
- Lee, D. S. et al. (2021). “The contribution of global aviation to anthropogenic climate forcing for 2000 to 2018.” Atmospheric Environment 244, 117834. doi:10.1016/j.atmosenv.2020.117834
FAQ
Frequently asked questions
How do I calculate my carbon footprint?
List your yearly electricity (kWh), natural gas (therms), gallons of fuel and flight miles, multiply each by its emission factor and add the results. With EPA factors that is kWh × 0.350, therms × 5.306, gallons × 8.78 and flight miles × 0.129 to 0.207, all in kg of CO2.
How much CO2 does 1 kWh of electricity produce?
On the US grid as a whole, about 0.350 kg (0.77 lb) of CO2 per kWh, based on the eGRID2023 US average total output rate of 771.5 lb CO2 per MWh. Your region can be much higher or lower, so enter your eGRID subregion rate if you know it.
How much CO2 does a gallon of gasoline produce?
Burning one gallon of motor gasoline releases 8.78 kg of CO2, according to the EPA GHG Emission Factors Hub. A car at 28 mpg therefore emits about 0.31 kg of CO2 per mile.
How much CO2 does a flight produce per mile?
The EPA lists 0.207 kg CO2 per passenger-mile for flights under 300 miles, 0.129 kg for 300 to 2,300 miles and 0.163 kg for 2,300 miles or more. 2,000 passenger-miles in the medium band is 258 kg.
Is this the EPA carbon footprint calculator?
No. The EPA publishes its own household calculator. This tool is independent, but it uses public EPA emission factors and shows every factor so you can check the maths.
Does this calculator include methane and other gases?
No, it counts CO2 only. Methane and nitrous oxide add a little for fuel combustion, and aircraft also have non-CO2 effects such as contrails, which are not included here.
5 Sources
- U.S. EPA, GHG Emission Factors Hub (2025)
- U.S. EPA, GHG Emission Factors Hub 2025 (PDF, January 2025; Table 6 reproduces eGRID2023)
- U.S. EPA, eGRID summary data
- U.S. EPA, Greenhouse Gas Equivalencies Calculator: calculations and references
- Lee et al. (2021), The contribution of global aviation to anthropogenic climate forcing, Atmospheric Environment
Last updated October 25, 2026. Part of our renewable energy toolkit. Found an error? Tell us.