Flight

Flight carbon calculator

Pick two airports and a cabin to see the CO2 your share of the flight puts out, one way or return, using the UK government's published factors.

John F. Kennedy International Airport, JFK
London Heathrow Airport, LHR
Cabin
Trip
Return trip, per passenger1.30 tCO2e, including the extra warming from contrails and other non-CO2 effects.
The CO2 alone
763 kg
Distance
5,540 km each way, long-haul
Against economy
Economy is the lowest per seat
Per km
117 g CO2e per passenger-km

From the UK government's 2025 conversion factors (DESNZ). Real flights vary with the aircraft, how full it is and the route flown.

Return flights, per passenger

Including non-CO2 effects, from the government factors:

RouteDistanceEconomyBusiness
London – Rome1,444 km363 kg545 kg
New York – Los Angeles3,974 km930 kg2.70 t
London – New York5,540 km1.30 t3.76 t
London – Dubai5,498 km1.29 t3.73 t
Los Angeles – Sydney12,061 km2.82 t8.19 t
Singapore – London10,883 km2.55 t7.39 t
New Delhi – London6,731 km1.58 t4.57 t
Frankfurt – New York6,189 km1.45 t4.20 t

How the estimate works

  • The distance is the great circle between the two airports, the shortest path over the globe. The factors already add the extra a real route takes, for air traffic and holding.
  • The factor depends on the flight: hops under 500 km, short-haul up to 3,700 km, and long-haul beyond, and on the cabin.
  • Non-CO2 warming is included at 1.7 times the CO2, as in the government's figures. The CO2 alone is shown beside the total.

Our article on a flight's carbon footprint covers what the numbers mean and what actually reduces them. For the distance on its own, use the flight distance calculator.

Questions

How is a flight's carbon footprint calculated?

Distance times an emission factor: the average greenhouse gas per passenger for each kilometre, which depends on the length of the flight and the cabin. We use the UK government's 2025 conversion factors (from DESNZ, the Department for Energy Security and Net Zero), which already allow for the extra distance real flights fly and include non-CO2 effects.

What are non-CO2 effects?

At cruising altitude, aircraft also emit nitrogen oxides and water vapour and form contrails, which add to warming on top of the CO2. Scientists are less certain about their size than about CO2's; the government factors count them as 1.7 times the CO2. The calculator shows the total and the CO2 alone.

Why does business class have a bigger footprint?

A business seat takes up several times the floor space of an economy seat, so it's allotted a bigger share of the plane's fuel. On long-haul flights the factors put business at about 2.9 times economy and first at about 4.

Why are short flights worse per kilometre?

Take-off and climb burn a lot of fuel, and on a short hop that's a big share of the trip. Long flights spread it over more distance, although carrying fuel for the whole trip offsets part of the gain.

How accurate is it?

It's an average for the distance and cabin. Your actual flight depends on the aircraft, how full it is, the route and the weather, and can easily differ by 20% or more either way.

Further reading

  1. What is the carbon footprint of a flight?A return flight across the Atlantic emits over a tonne of CO2e per economy passenger. How flight emissions are calculated, what non-CO2 effects add, and how to cut them.

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