Flight CO2 Calculator

How to use it

1. Type the codes in Departure airport and Arrival airport, such as LHR and IST. Or leave both empty and type a distance in Distance, without airports.
2. Choose the Haul and the Cabin class of the flight you are measuring.
3. Set Trip to Return for a round trip, and enter the number of Passengers.
4. Read kg CO2e per passenger and kg CO2e for all passengers. Open How the result is worked out to see each step and factor.

How the emissions are calculated

The calculator multiplies the distance by the factor for the haul and cabin, and then by the number of passengers. The factors are the UK government's conversion factors for business travel by air, published for company reporting in 2026 by DESNZ, the Department for Energy Security and Net Zero.

The distance is the great-circle distance between the two airports: the shortest line over the surface of the Earth. It is calculated with the haversine formula on a sphere of mean radius 6,371.0088 km. The factors already include an 8% allowance for indirect flight paths, delays and circling, so no extra distance is added here. This is the UK method, not the ICAO Carbon Emissions Calculator method.

emissions = distance × factor × passengers

distance     great-circle km, one way (doubled for a return trip)
factor       kg CO2e per passenger-km for the haul and cabin
passengers   number of people on the trip

• The distance is rounded to whole kilometres before the calculation.
• Domestic flights have only an average factor, so the average is used for every cabin.
• Short-haul flights have no factor for premium economy or first class. The calculator says so rather than guessing a figure.

Radiative forcing: which factor to use

Flying warms the climate through effects beyond CO2, such as water vapour, contrails and nitrogen oxides. The UK factors come in two sets: one includes these indirect effects of non-CO2 emissions, and one counts the direct effects only. The workbook applies the indirect effects to the CO2 factor as an increase of 70%, which is why the set with radiative forcing is about 1.7 times the direct-only set.

The calculator shows both. The main result, per passenger and for all passengers, uses the set with radiative forcing, because DESNZ advises that users should generally use it. The direct-only figure is there for comparison, and for reporting rules that leave these effects out. The size of the indirect effects is still a subject of significant scientific uncertainty.

What the result does not cover

• The journey to and from the airport by taxi, car or train, and the emissions of the airports themselves. These are not added to the factor.
• Freight. The factors are for passengers; cargo has its own factors in the same workbook.
• The upstream emissions of producing and transporting the fuel. DESNZ publishes them on a separate sheet, WTT- business travel- air, which this calculator does not add.
• Connecting flights. Each calculation covers one flight between two airports, so enter each flight separately and add the results.
• Mixed cabins. The calculator works with one cabin at a time. If you flew in two classes, calculate each part and add them.

How the haul is set

The DESNZ methodology (paragraphs 8.8 and 8.9) defines the haul by the route. Flights between the UK and Europe (excluding Moldova and Ukraine, but including Gibraltar, Greenland and Turkey) and between the UK and North Africa (Algeria, Egypt, Libya, Morocco and Tunisia) are short-haul. Other flights from or to the UK are long-haul, and flights between non-UK destinations are international.

Earlier versions suggested splitting flights at 3,700 km. The methodology calls that approach relatively simplistic and uses the route rule instead, so this calculator does not use the distance split. The calculator follows the haul you choose; it does not read the countries of the airports.

Frequently asked questions