Flight Carbon Footprint Calculator
Enter airport codes to get CO2 equivalent emissions per passenger based on seat class, using DEFRA/ICAO methodology. Includes radiative forcing for non-CO2 high-altitude effects and offset cost estimate. Nothing uploaded.
Flight Details
Advanced options
Emissions
Enter airports above.
Learn more: how flight emissions are estimated
How the calculator builds the number
The calculator finds the great-circle distance between the two airports, adds 8% for non-direct routing and holding, and multiplies by an emission factor for your seat class. London Heathrow to New York JFK is 5,539 km in a straight line, which becomes 5,983 km after the uplift.
A round trip counts as two full legs, so it is exactly double the one-way figure. The total is the per-passenger figure times the number of passengers.
Seat class and the emission factors
A seat that takes more space and weight is allocated a larger share of the flight's emissions. The calculator uses the UK government's DEFRA 2025 long-haul factors as summarized by greencalculus.com in its table of flight emission factors: 0.117 kg CO2e per passenger-kilometer for economy, 0.187 for premium economy, 0.339 for business and 0.468 for first class. Those figures include radiative forcing, an uplift of about 70% for non-CO2 effects.
The ratios to economy are 1.6, 2.9 and 4.0. To let you switch the uplift on and off, the calculator divides each factor by 1.7 to get a CO2-only value, then applies your chosen setting. It uses the long-haul factors for every distance, so short flights are only approximate.
The radiative forcing option
You can choose none, medium (1.7 times, DEFRA's uplift) or high (2.7 times). For one economy passenger from Heathrow to JFK that gives about 412 kg CO2e with none, 700 kg at medium and 1,112 kg at high. Business class at medium is about 2,028 kg and first class about 2,800 kg.
How large the non-CO2 effects are is uncertain. Published factors also change from year to year, so for carbon reporting use the current official conversion factors, such as the UK government's DEFRA set, instead of this estimate.
FAQ
Why is business class about 2.9 times economy?
The calculator's factors follow DEFRA's cabin ratios, which reflect the larger share of the aircraft's space and weight a business seat is allocated. They are allocation factors, not a measurement of any one flight.
What does the radiative forcing option cover?
It covers climate effects of flying at altitude other than CO2, mainly contrails and other atmospheric effects. How large those effects are is uncertain, which is why the calculator offers a medium and a high setting as well as none.
Does a round trip just double the one-way figure?
Yes. The calculator counts a round trip as two legs of the same distance and the same factor, so the total is exactly twice the one-way estimate.