Flight carbon emissions calculator

Factors come from the DESNZ 2025 (published June 2025) conversion factors (gov.uk, business travel air and its well-to-tank counterpart), and that file is the only source this tool uses: no live service, no airline data. The two headline numbers differ because the with-RF figure applies a 1.7 multiplier for aviation's indirect effects, which DESNZ recommends while flagging real scientific uncertainty, so neither number is the truth and the pair is the honest answer. Distances are great-circle lines between reference points with the standard 8 percent routing uplift already inside the factors; winds, airways and the actual aircraft type are not modelled, and calculators using ICAO or other factor sets can land 30 percent away. Domestic flights publish one average-passenger factor, so a cabin pick there falls back with a note.