Driving CO₂ calculator
Enter your miles and mpg, get the CO₂.
How much CO₂ does a gallon of gas make?
The EPA says burning a gallon of gasoline produces 8,887 grams of CO₂ — about 19.6 pounds. A gallon of diesel produces 10,180 grams, about 22.4 pounds.
How do I calculate my car’s emissions?
Divide miles by your mpg to get gallons, then multiply by the grams per gallon. 11,500 miles at 22.2 mpg burns 518 gallons of gasoline: about 4.6 metric tons of CO₂.
What is typical for a passenger car?
The EPA puts a typical passenger vehicle at about 400 grams of CO₂ per mile and 4.6 metric tons a year, assuming 22.2 mpg and 11,500 miles.
Does this include other greenhouse gases?
No — only CO₂ from the tailpipe. Methane, nitrous oxide and the emissions from producing the fuel are not included.
How can I cut it?
Every gallon you do not burn saves 8,887 grams of CO₂: drive fewer miles, or choose a vehicle with higher mpg.
Worked example: a 30 mpg car and a diesel
A gasoline car that drives 12,000 miles at 30 mpg burns 12,000 ÷ 30 = 400 gallons. At 8,887 grams per gallon that is 3,554,800 grams, or 3.55 metric tons, 296 grams per mile. The same distance at the EPA’s typical 22.2 mpg gives 4.80 metric tons, so the more efficient car emits 26% less. A diesel driven 8,000 miles at 25 mpg burns 320 gallons at 10,180 grams each: 3.26 metric tons, 407 grams per mile.
Why does CO₂ track fuel burned so closely?
The EPA’s per-gallon figures come from the carbon content of the fuel, on the assumption that all of it is converted to CO₂, so the emissions are proportional to the gallons burned. Cutting fuel use by a given percentage cuts tailpipe CO₂ by the same percentage. A gallon of diesel gives 14.5% more CO₂ than a gallon of gasoline, so a diesel needs better mileage to break even. The EPA’s page on the typical vehicle (updated June 2026) says its 400 g/mile and 4.6 tons a year cover CO₂ only; methane and nitrous oxide from the tailpipe and air-conditioning leaks add warming but are small compared with CO₂.
Worked example: a daily commute
A 25-mile commute each way, 250 working days a year, is 25 × 2 × 250 = 12,500 miles. In a 28 mpg gasoline car that burns 446 gallons and produces 3.97 metric tons of CO₂, about 79 kilograms a week and 317 grams per mile. Working from home one day a week removes a fifth of those miles and a fifth of the CO₂, since the emissions are proportional to the distance for a given car.
How do I convert mpg to liters per 100 km?
Divide 235.215 by the mpg (US gallons): 30 mpg is 7.8 L/100 km. The conversion works the other way too, 235.215 ÷ L/100 km, and a lower L/100 km is better, while a higher mpg is better. Convert before using the calculator if your car is rated in L/100 km.
Common mistakes with driving emissions
Mixing units: a metric ton is 1,000 kg, about 2,204.62 pounds, not the 2,000-pound US ton. Using the diesel figure for gasoline or the reverse. Entering liters per 100 km as if it were mpg; convert first. Treating the result as the whole footprint: fuel production, the vehicle’s manufacture and other greenhouse gases are not included. Comparing with an electric car on tailpipe alone: an EV has no tailpipe CO₂, but its electricity has its own emissions. And forgetting that real mpg differs from the label.
Sources and related calculators
Sources: U.S. Environmental Protection Agency, “Greenhouse Gas Emissions from a Typical Passenger Vehicle” (8,887 and 10,180 grams of CO₂ per gallon, 400 grams per mile, 4.6 metric tons a year at 22.2 mpg and 11,500 miles; page updated June 3, 2026). Related: fuel cost calculator, gas mileage calculator, EV vs gas calculator and MPGe calculator.