✈️ Flight Emissions Calculator
Enter a flight's distance, passengers, and cabin class to estimate its CO2 emissions per passenger and in total — with a round-trip option — so you can weigh the climate cost of a journey before you book.
✈️ Estimate a Flight's CO2
What is a Flight Emissions Calculator?
Air travel is one of the most carbon-intensive things an individual can do, and its footprint is easy to underestimate. This calculator estimates a flight's emissions from three inputs (how far you fly, how many people are travelling, and which cabin you sit in) using the UK DESNZ 2025 conversion factors, which change with the length of the flight and the seat.
Use it to compare routes, decide between a direct flight and a connection, or weigh a trip against lower-carbon alternatives like rail. Each result is shown with and without the radiative-forcing multiplier; both are planning estimates, and the real figure depends on the aircraft, how full it is, and the route flown.
❓ Frequently Asked Questions
How are flight emissions calculated?
It multiplies the great-circle distance by a UK DESNZ 2025 conversion factor in kg CO2e per passenger-kilometre, chosen by distance and cabin: the domestic factor for hops of 500 km and under, the short-haul factor up to 3,700 km, and the long-haul factor beyond (close to the 300-mile and 2,300-mile splits the US EPA's Emission Factors Hub uses). Short flights burn more per kilometre because take-off and climb are a bigger share of the trip, so a 400 km hop comes out at about 0.23 kg per km with radiative forcing against about 0.12 kg on a long-haul economy seat. A return trip counts both legs, and the total multiplies by the number of passengers. The DESNZ factors already add 8% for indirect routing, so do not add your own uplift.
Why do business and first class emit more than economy?
Premium seats take up more of the cabin, so each passenger carries a larger share of the fuel burn. On long-haul flights the DESNZ factors put premium economy at 1.6 times economy, business at 2.9 times and first at 4 times. On short-haul flights the gap is smaller: DESNZ publishes one business row at 1.5 times economy, which this tool also uses for premium economy and first. On the shortest hops DESNZ publishes a single average for every seat.
Does flying really matter that much for the climate?
For people who fly, it is often the single largest part of their carbon footprint. One long-haul return flight can emit more than a tonne of CO2 per passenger — comparable to months of driving or a large share of an average person's annual budget. Flying less, choosing direct routes, and travelling in economy are the most effective ways to cut aviation emissions.
Does this include the non-CO2 warming effect of flying?
Yes, as a separate figure. Aircraft also create contrails and release nitrogen oxides and water vapour at altitude, which add to warming. DESNZ recommends a multiplier of 1.7 on the CO2 as a central estimate and notes it is uncertain. The headline result includes it; the direct-only figure, which is what most airline and booking-site numbers show, leaves it out. Quote whichever you use by name, because the two differ by about 70%.