How to use this calculator
Enter the trip distance and your car's fuel economy — in US mpg, UK mpg, km/L or L/100 km. The emission factor is pre-filled with the EPA value for gasoline, 8,887 grams of CO₂ per gallon; for diesel, replace it with 10.18 kg/gal (2.69 kg/L). Add passengers to see the share per person.
You can also start from fuel receipts: enter the gallons or liters you bought to get the CO₂ directly, or enter both distance and fuel to compute the real-world fuel economy of a trip. Because fuel economy units are converted exactly, the calculator doubles as an mpg ↔ L/100 km converter.
The formula
- d
- trip distance
- e
- fuel economy
- F
- fuel burned
- k
- co₂ per unit of fuel
- CO₂
- co₂ emitted
- n
- people sharing the car
- CO₂/n
- co₂ per person
Worked example
Two friends drive 300 miles in a car that averages 30 mpg on gasoline.
- Fuel = 300 mi ÷ 30 mpg = 10 gal.
- CO₂ = 10 gal × 8.887 kg/gal = 88.9 kg.
- Per person = 88.9 ÷ 2 = 44.4 kg.
The trip emits about 89 kg (196 lb) of CO₂, or 44 kg each.
Assumptions and limits
- Tailpipe CO₂ only. Upstream emissions from producing and transporting fuel add roughly 20–25%, and other greenhouse gases (methane, N₂O) add a small amount.
- Fuel economy is the trip average; city driving, speed, load and cold weather can change it by 10–30%.
Frequently asked questions
How much CO₂ does a gallon of gasoline produce?
Burning one US gallon of gasoline releases about 8,887 g (19.6 lb) of CO₂ according to the EPA; a gallon of diesel releases about 10,180 g.
How do I convert mpg to L/100 km?
Divide 235.215 by the US mpg figure. 30 mpg = 7.84 L/100 km. Select the units here to convert automatically.
What is the average car’s CO₂ per mile?
The EPA estimates about 400 g of CO₂ per mile for a typical US passenger vehicle at around 22 mpg.