Driving Carbon Footprint Calculator
Estimate the CO₂ your car emits each year from your annual mileage and fuel economy, using the EPA gasoline emission factor.
How it works
Gallons = miles ÷ mpg · CO₂ (kg) = gallons × 8.887
Burning one US gallon of gasoline releases about 8.887 kg of CO₂ — a fixed figure set by the carbon in the fuel, not by the engine. So your driving footprint depends only on how far you drive and how many miles you get per gallon. Improving fuel economy or cutting mileage lowers emissions in direct proportion.
Worked example
At 12,000 miles a year and 25 mpg you burn 12,000 ÷ 25 = 480 gallons. Multiplied by 8.887 kg, that is about 4,266 kg — roughly 4.27 tonnes of CO₂ per year.
Sources: EPA — Greenhouse Gas Emissions from a Typical Passenger Vehicle
Frequently asked questions
Where does 8.887 kg per gallon come from?
It is the US EPA figure for CO₂ produced by completely burning one gallon of gasoline. The carbon in the fuel combines with oxygen, so the CO₂ mass is actually larger than the fuel mass.
Does this include making the fuel?
No — this is tailpipe (combustion) CO₂ only. Extracting, refining and delivering the fuel adds roughly 20–25% more on a well-to-wheel basis, and manufacturing the vehicle is separate again.
What about diesel or hybrids?
Diesel emits about 10.18 kg CO₂ per gallon, so this gasoline factor understates diesel slightly. For a hybrid, use its real-world combined mpg and the calculator still applies.
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This calculator is for educational purposes. Double-check important results before acting on them.