Calculate the carbon footprint of driving from your distance and fuel economy for a single trip or a full year, with gasoline, diesel, and electric modes.
Carbon Footprint of Driving Formula
CO2 = (D / MPG) * EF
CO2 (EV) = (D / e) * GF
- CO2 is the carbon dioxide emitted, in kilograms
- D is the distance driven, in miles
- MPG is the fuel economy of the vehicle, in miles per gallon
- EF is the fuel emission factor: 8.887 kg CO2 per gallon of gasoline or 10.18 kg CO2 per gallon of diesel (EPA values)
- e is the electric vehicle efficiency, in miles per kWh
- GF is the grid carbon intensity, in kg CO2 per kWh of electricity
If you work in metric, the same math applies with liters: fuel used equals kilometers driven times the L/100 km rating divided by 100, and each liter of gasoline produces about 2.35 kg of CO2 (2.69 kg for diesel).
The calculator applies these formulas in three modes. Trip mode multiplies the fuel or electricity used on a single journey by the matching emission factor. Annual mode runs the same calculation over a full year of driving and reports the result in metric tons. Comparison mode computes the gasoline formula and the EV formula over the same annual distance and shows the difference, which tells you how much CO2 switching to an electric car would save on your grid. The advanced options extend the formulas in two ways: selecting the upstream scope multiplies gasoline and diesel results by 1.25 to account for producing and delivering the fuel, and entering a passenger count divides the total by the number of people to give a per person footprint for carpooling.
Emission Factors and CO2 per 1,000 Miles
The first table lists the emission factors the calculator uses. Tailpipe values cover only the CO2 released while driving. The well-to-wheel column adds roughly 25 percent for extracting, refining, and transporting the fuel. For electricity there is no tailpipe value, so the grid factor itself is the well-to-wheel number.
| Energy source | Tailpipe factor | Well-to-wheel estimate |
|---|---|---|
| Gasoline | 8.887 kg/gal (2.35 kg/L) | about 11.1 kg/gal |
| Diesel | 10.18 kg/gal (2.69 kg/L) | about 12.7 kg/gal |
| Electricity, US average grid | 0 (no tailpipe) | 0.37 kg/kWh |
| Electricity, low-carbon grid | 0 | about 0.10 kg/kWh |
| Electricity, coal-heavy grid | 0 | about 0.75 kg/kWh |
The second table shows what those factors mean over 1,000 miles of driving at common efficiency levels, so you can place your own result in context.
| Vehicle | Tailpipe CO2 per 1,000 mi | Well-to-wheel per 1,000 mi |
|---|---|---|
| Full-size truck, 15 MPG | 592 kg | 741 kg |
| Typical US car, 22.2 MPG | 400 kg | 500 kg |
| Efficient sedan, 30 MPG | 296 kg | 370 kg |
| Diesel sedan, 30 MPG | 339 kg | 424 kg |
| Hybrid, 50 MPG | 178 kg | 222 kg |
| EV, 3 mi/kWh, US grid | 0 kg | 123 kg |
| EV, 4 mi/kWh, US grid | 0 kg | 93 kg |
Carbon Footprint of Driving Example Problems
Example 1: You drive a 30 mile round trip commute in a gasoline car that averages 28 MPG. Fuel used is 30 / 28 = 1.071 gallons. CO2 is 1.071 * 8.887 = 9.52 kg for the trip, or about 21 pounds. With one coworker carpooling, the per person footprint drops to 4.76 kg.
Example 2: You drive 11,500 miles per year in a car that averages 22.2 MPG. Fuel used is 11,500 / 22.2 = 518 gallons. CO2 is 518 * 8.887 = 4,604 kg, or about 4.6 metric tons per year, which matches the EPA figure for a typical US passenger vehicle. Offsetting that year of driving would take roughly 77 tree seedlings grown for 10 years.
Carbon Footprint of Driving FAQ
Is an electric car really lower carbon than a gasoline car? On the US average grid, yes, by a wide margin. Driving 11,500 miles at 3.3 mi/kWh uses about 3,485 kWh, which produces roughly 1,289 kg of CO2 at 0.37 kg/kWh, about 72 percent less than the 4,604 kg from a 22.2 MPG gasoline car. Even on a coal-heavy grid at 0.75 kg/kWh, the EV comes in near 2,614 kg, still well below the gasoline car. Use the comparison mode with your own grid factor to see your local numbers.
Why does my result say CO2 instead of CO2e? CO2 makes up about 95 to 99 percent of the greenhouse gases from a car’s tailpipe. The remainder is methane, nitrous oxide, and leaked air conditioning refrigerant. This calculator reports CO2 only, so a full CO2e figure would be slightly higher.
What are the fastest ways to shrink your driving footprint? The result scales directly with distance and inversely with fuel economy, so the biggest levers are driving fewer miles and raising your effective MPG. Combining errands into one trip, keeping tires inflated, avoiding aggressive acceleration, and holding highway speeds near the limit each improve real-world economy by a few percent. Carpooling cuts the per person number in proportion to riders, which the advanced options can show you directly.
