Fuel CO₂ Emissions
CO₂ from fuel burned — litres, gallons, kg or consumption × distance — from the fuel density and carbon fraction or an emission factor you enter; g/km, tonnes.
Fuel mass and carbon mass, CO₂ in kg and tonnes, the factor per litre and per kg, and with a distance the grams per km and per mile and kg per 100 km.
Example: 50 L at 0.745 kg/L and 87 % carbon: 37.25 kg fuel → 32.4 kg carbon → 118.7 kg CO₂ (2.37 kg/L); over 600 km that is 198 g/km.
Carbon in,
3.66 times as much CO₂ out.
The chemistry that is fixed, the fuel data that is yours, and what an emission factor may or may not include.
The fixed part
Every kilogram of carbon burned completely becomes 44.0095 ÷ 12.011 = 3.664 kg of CO₂ — the ratio of the molar masses, the one number the page knows. Fuel mass = volume × density; carbon = fuel mass × carbon mass fraction; CO₂ = carbon × 3.664. Volumes convert at 3.785411784 L per US gallon and 4.54609 L per UK gallon.
Your fuel data
Density and carbon fraction come from the fuel specification or the inventory method you follow; a quoted emission factor (kg CO₂ per litre or per kilogram) can be entered instead and is applied as given. Nothing is embedded for petrol, diesel, LPG or blends, because the values differ by grade, season, region and accounting convention. With a density entered, the page links litres and kilograms so either factor works on either quantity.
Reading the result
Tailpipe CO₂ from complete combustion excludes fuel production and delivery (well-to-tank), CO, hydrocarbons and soot, and any biogenic accounting for biofuel blends. A distance turns the total into g/km, g/mile and kg per 100 km; consumption × distance gives the litres directly. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- CO₂ = carbon mass × 44.0095/12.011 (complete combustion); carbon = fuel mass × carbon fraction; fuel mass = litres × density; 1 US gal = 3.785411784 L, 1 UK gal = 4.54609 L
Last reviewed 21 September 2026. How results are checked: How we verify.