Carbon Footprint Calculator
Estimate your yearly carbon footprint in tons of CO2 from your car, home energy, and flights — see where your emissions come from.
Reviewed by the CalcCafe editorial team · Last updated 1 July 2026 · How we test our tools
Example
Driving 12,000 miles at 25 MPG burns 480 gallons, and at 8.89 kg CO2/gallon that is 4.27 t. Adding 10,000 kWh of electricity (×0.40) = 4.00 t, 400 therms of gas (×5.30) = 2.12 t, and 10 flight hours (×90) = 0.90 t gives a total of 11.29 tonnes CO2/yr, of which 6.12 t is home energy.
How it works
Car CO2 = (miles ÷ MPG) × 8.89 kg/gallon; grid electricity = kWh × 0.40 kg; natural gas = therms × 5.30 kg; flights = flight-hours × 90 kg. Total kg is the sum of all four, and tonnes = total kg ÷ 1,000. Home energy combines grid electricity and natural gas.
Good to know
A carbon footprint is the total amount of greenhouse gas, expressed as carbon dioxide, that your activities put into the atmosphere over a year. This tool focuses on the four sources that dominate most household footprints in developed countries: the fuel your car burns, the electricity you pull from the grid, the natural gas you burn for heat and hot water, and the flights you take. Each input is multiplied by a standard emission factor and the results are added into one annual figure in tonnes.
The emission factors here are rounded averages. Burning a gallon of gasoline releases about 8.89 kg of CO2, a therm of natural gas about 5.3 kg, and a rough all-in figure of 90 kg per hour of flying captures the outsized impact of air travel. The electricity factor of 0.40 kg per kWh is a mid-range grid average; a coal-heavy region can be well above it, while a grid rich in hydro, nuclear, or renewables can be far below. If you know your utility's published figure, the real number for your home may differ.
Treat the total as a directional estimate, not an audited inventory. It deliberately leaves out the embedded carbon in the food you eat, the goods you buy, public transit, and home construction, so your true footprint is almost certainly larger. Its value is in comparison: change one input and watch which lever moves the needle most. For many people, cutting a couple of long flights or switching to a more efficient vehicle shifts the total more than months of smaller habit changes.
Use it to set priorities and to sanity-check claims about which changes matter, then confirm specifics — your grid mix, your car's real-world economy, actual flight emissions — with primary sources before making big decisions.
Frequently asked questions
What counts as a good carbon footprint?
The global average is roughly 4-5 tonnes of CO2 per person per year, while the U.S. average is much higher, around 15-16 tonnes. Climate targets point toward about 2 tonnes per person by mid-century, so lower is better — but focus on your biggest sources first.
Why is flying weighted so heavily?
Air travel is energy-intensive per hour, and this tool uses a rough all-in factor of 90 kg CO2 per flight hour. A few long-haul trips can rival or exceed a full year of driving, which is why cutting flights often moves the total the most.
Is my data uploaded anywhere?
No — this calculator runs entirely in your browser. Your inputs never leave your device, and it works offline once loaded.
Is this calculator free?
Yes, completely free with no sign-up and no limits.
People also ask
How do you calculate a carbon footprint?
Multiply each activity by an emission factor: gallons of gasoline by 8.89 kg, kWh of electricity by about 0.40 kg, therms of gas by 5.30 kg, and flight hours by roughly 90 kg. Add them up and divide by 1,000 to get tonnes of CO2 per year.
How much CO2 does driving a car produce?
About 8.89 kg of CO2 per gallon of gasoline burned. At 25 MPG, driving 12,000 miles a year uses 480 gallons and emits roughly 4.3 tonnes of CO2.
What is the biggest source of a household carbon footprint?
For most households it is transportation and home energy — driving, heating, and electricity — with air travel adding a large spike for frequent flyers. This tool breaks out driving, home energy, and flights so you can see which dominates yours.
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Sources & references
These tools follow our methodology and provide educational estimates only — verify important figures with a qualified professional.