Question 1

How is car CO2 emissions calculated?

Accepted Answer

For gasoline, diesel, and hybrid cars, the calculator divides your distance by your fuel economy to find out how much fuel you burned, then multiplies that by a fixed emission factor (8.887 kg CO2 per US gallon of gasoline, 10.180 kg CO2 per US gallon of diesel, per EPA figures). For electric vehicles, it multiplies the energy drawn from the battery (distance ÷ efficiency) by your electricity grid's carbon intensity.

Question 2

Why do hybrid and gasoline cars use the same emission factor?

Accepted Answer

Both burn the same gasoline, so each gallon releases the same amount of CO2 when combusted. A hybrid's lower real-world footprint comes entirely from using less fuel per mile (better MPG), not from the fuel itself being cleaner — this calculator reflects that by applying your hybrid's actual fuel economy.

Question 3

What electricity grid carbon intensity should I use for my EV?

Accepted Answer

Grid carbon intensity (grams of CO2 per kWh) varies a lot by region and energy mix. Use the presets provided as a rough starting point — US average, EU average, UK average, a coal-heavy grid, or a mostly-renewable grid — or look up your local utility's or grid operator's published carbon-intensity figure for a more accurate result.

Question 4

How accurate are these results?

Accepted Answer

The combustion emission factors come from published EPA figures and are exact for the CO2 released per gallon of fuel burned. Accuracy depends on how precisely you know your real-world fuel economy or EV efficiency, and — for EVs — how accurate your grid intensity estimate is. This tool is for informational and planning purposes, not for regulatory or legal emissions reporting.

Question 5

Can I use this for my annual driving total, not just one trip?

Accepted Answer

Yes — enter your total annual mileage (or kilometers) as the distance instead of a single trip's distance, and the calculator will give you your estimated annual CO2 footprint from driving using the same formula.

Question 6

What counts as a "Low", "Average", or "High" result?

Accepted Answer

The rating compares your CO2-per-mile (or per-km) rate against the EPA's typical passenger vehicle average of about 400 g CO2 per mile (≈249 g CO2 per km). Rates notably below that average are rated Low, rates notably above are rated High, and rates close to it are rated Average.

Car CO2 Emissions & Carbon Footprint Calculator

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How This Calculator Works

Frequently Asked Questions

How is car CO2 emissions calculated?

Why do hybrid and gasoline cars use the same emission factor?

What electricity grid carbon intensity should I use for my EV?

How accurate are these results?

Can I use this for my annual driving total, not just one trip?

What counts as a "Low", "Average", or "High" result?

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