About the Flight Carbon Calculator
This flight carbon calculator estimates the greenhouse-gas emissions of air travel from the flight distance, whether it is one-way or return, the cabin class and the number of passengers. It reports kilograms of CO2-equivalent (CO2e) per passenger and in total, plus a rough offset cost and an equivalent driving distance.
Use it to compare trips, to decide between flying and a train or car, for business travel reporting, or to size a carbon offset purchase. Premium cabins take up more floor space per seat, so their share of the aircraft’s fuel burn — and emissions — is higher.
The per-kilometre factors are the UK government’s 2026 greenhouse-gas conversion factors for business travel (DESNZ, 2026 edition, the latest published). They are applied to the great-circle distance and already include DESNZ’s 8% uplift for indirect routing and delays. With radiative forcing switched on, the DESNZ “with RF” factors are used; these apply a 1.7 multiplier to the CO2 part to reflect contrails and nitrogen oxides at altitude. Flights under 500 km use the DESNZ domestic factor, and the 3,700 km boundary between medium and long haul follows DESNZ. The under-500 km band is this tool’s own simplification, not a DESNZ category. Results are estimates; the exact figure varies by aircraft, load factor and route.
With the default inputs, the total emissions is 1,287 kg CO2e. Change any value above to recalculate instantly.
How to use the flight carbon calculator
- 1Enter the one-way distance between the airports and pick km or miles.
- 2Choose return or one-way, and your cabin class.
- 3Enter the number of passengers travelling.
- 4Decide whether to include radiative forcing for the full climate impact.
- 5Read the total CO2e, and compare cabin classes on the chart.
Formula and method
The great-circle distance d is multiplied by the number of legs (2 for a return trip) and by a DESNZ 2026 emission factor per passenger-kilometre. The factor already includes an 8% uplift for real flight paths, holding patterns and diversions, so no extra distance is added. Without radiative forcing, flights under 500 km use the DESNZ domestic factor of 0.13552 kg CO2e/km, because take-off and climb burn a lot of fuel. Economy uses 0.07435 kg for 500–3,700 km and 0.06926 kg over 3,700 km.
Premium cabins get higher factors because each seat takes more floor space. Long-haul figures are 0.11081 kg for premium economy (1.6×), 0.20083 kg for business (2.9×) and 0.27701 kg for first (4×). On 500–3,700 km flights, business and first both use 0.11152 kg (1.5×) and premium economy uses the economy factor, because DESNZ publishes no separate figures for them. Under 500 km there is no class split. With radiative forcing on, the DESNZ “with RF” factors apply a 1.7 multiplier to the CO2 component, for example 0.11704 kg for long-haul economy. This is DESNZ’s central estimate of the warming from contrails and NOx at altitude, and it is highly uncertain.
- d
- Great-circle distance of one leg, km
- EF
- DESNZ 2026 kg CO2e per passenger-km for the distance band and cabin, with or without radiative forcing
- legs
- 1 for one way, 2 for a return trip
Worked examples
New York to London return, economy
The return trip is 2 × 5,500 = 11,000 km great-circle. The DESNZ long-haul economy factor with radiative forcing is 0.11704 kg CO2e per passenger-km, so the trip produces about 1,287 kg (1.29 t), or 762 kg at 0.06926 kg without radiative forcing. Offsetting 1.29 t at $15 per tonne costs about $19.31, and the total equals driving an average petrol car (0.16152 kg/km) about 7,971 km.
800-mile business trip, two travellers, one way
800 miles is 1,287.5 km, a medium-haul flight. Without radiative forcing, the DESNZ short-haul business factor is 0.11152 kg CO2e per passenger-km, 1.5 times economy. That gives 143.6 kg each, or 287 kg for two travellers.
Short 350 km hop for a family of four
A 350 km return trip is 700 km per person. Flights under 500 km use the DESNZ domestic factor, 0.22928 kg per passenger-km with radiative forcing. That is nearly double the long-haul economy rate. Each passenger emits about 160.5 kg and the family about 642 kg, which is why rail is usually far cleaner on short routes.
Frequently asked questions
How much CO2 does a flight produce per passenger?+
Using the UK government’s 2026 factors, economy passengers account for about 0.07 kg of CO2e per kilometre on longer flights and about 0.14 kg on short domestic hops, before adjusting for non-CO2 effects. A 5,500 km transatlantic return flight in economy is therefore about 0.76 tonnes per person, or about 1.29 tonnes with radiative forcing included.
What is radiative forcing in flight emissions?+
Aircraft emit nitrogen oxides, water vapour and form contrails at high altitude, which add warming on top of the CO2 itself. The UK government’s 2026 conversion factors apply a multiplier of 1.7 to the CO2 part as a central estimate (older methods often used 1.9); the science is still uncertain, so this tool lets you switch it on or off.
Why does business class have a bigger carbon footprint?+
Emissions are shared out by the space each seat occupies. A lie-flat business seat takes several times the floor area of an economy seat, so each business passenger is responsible for a larger share of the fuel burned.
Are short flights worse for the climate per kilometre?+
Yes. Take-off and climb burn a disproportionate amount of fuel, so short flights emit more per kilometre than long cruises. For trips under about 500 km, trains and even cars with passengers usually emit less.
Do carbon offsets cancel out my flight?+
Offsets fund projects that reduce or remove emissions elsewhere, but quality varies widely. Reducing the number of flights, flying economy and choosing direct routes cut emissions directly; offsets are best seen as a supplement.