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Flight carbon calculator: how much CO₂ is your flight?

Pick two airports and get an estimate of the emissions per passenger, one way or return, with the method and every factor shown — because the same flight can come out three times higher on one calculator than another.

Great circle
5,540 km
3,442 mi each way
Factor used
Long-haul
economy · DESNZ 2026

See this route on the globe →London – New York write-up →

Estimate · per passenger, return

≈ 1.57 tCO₂e

Includes non-CO₂ warming (×1.7) and producing the fuel. 785 kg each way.

CO₂ only, as ICAO counts it: ≈ 756 kg Why the two differ

To put that in context

  • 33%of the average person's CO₂ for a whole year (4.7 t)
  • 63%of a 1.5 °C-compatible yearly footprint (2.5 t)
  • 7,480 kmdriven alone in an average car, for the same emissions

An average for the distance, not a measurement of your flight. The aircraft, how full it is and the route flown all move the real number.

The footprint of some familiar flights

Per economy passenger, on the method below.

FlightDistanceOne wayReturn
London to Paris348 km52 kg103 kg
London to Barcelona1,148 km170 kg340 kg
New York to Los Angeles3,974 km563 kg1.13 t
London to Dubai5,498 km779 kg1.56 t
London to New York5,540 km785 kg1.57 t
London to Singapore10,883 km1.54 t3.08 t
Sydney to Los Angeles12,061 km1.71 t3.42 t
Paris to Tokyo9,708 km1.38 t2.75 t
Methodology

How the estimate is worked out

1. Distance. The great-circle distance between the two airports — the shortest path over the Earth, the same figure as the flight distance calculator. Planes fly a little further than this; the factors below already allow 8% for it.

2. Factor. Flights under 3,700 km use the UK government’s short-haul economy factor, longer ones the long-haul factor. DESNZ draws that line by region rather than distance; the 3,700 km cut-off is our approximation of it for flights anywhere in the world.

3. What’s counted. The CO₂ from burning the fuel, multiplied by 1.7 for non-CO₂ warming (contrails and nitrogen oxides at altitude), plus the emissions from extracting, refining and moving the fuel. Per economy seat, averaged over typical load factors.

4. Return trips are two one-way legs.

Emission factors used, kg CO₂e per passenger-kilometre
Per passenger-kmShort-haulLong-haul
Flight, with non-CO₂ (×1.7)0.125760.11704
Fuel production0.022490.02461
CO₂ only (ICAO basis)0.073440.06826
Headline total148 g142 g

kg CO₂e per passenger-km, economy, DESNZ 2026.

Why calculators disagree

Almost all of the spread is in what gets counted, not in the physics. The ICAO calculator reports only the CO₂ from burned fuel. Google Flights, through its open Travel Impact Model, adds the emissions from producing the fuel. The UK government multiplies the CO₂ by 1.7 for non-CO₂ effects; myclimate and atmosfair multiply by 3. For London to New York and back, that is the difference between about 756 kg and well over two tonnes.

Non-CO₂ effects are real — the best current estimate, Lee et al. (2021), puts them at about two-thirds of aviation’s warming — but far less certain than CO₂’s. Leaving them out understates a flight; multiplying by 3 is at the top of the range. This calculator takes the UK government’s middle course and shows the CO₂-only number beside it, so you can compare with whichever calculator you saw last.

The comparisons

  • The average person’s year is 4.73 t of CO₂ (world, 2024, Global Carbon Budget). That figure leaves out international flights, so it is a yardstick, not a like-for-like total.
  • A 1.5 °C-compatible year is 2.5 t CO₂e per person by 2030 (Hot or Cool Institute).
  • The car is the UK average car, tailpipe plus fuel production — 210 g CO₂e per km, one person in it.
  • The train is UK national rail at 40 g CO₂e per passenger-km over the same distance, shown only when both airports are on the same continent and under 1,500 km apart. Many European high-speed lines run lower than this.

Factors from UK Government GHG Conversion Factors 2026 (DESNZ) and its methodology paper. Cabin class and passenger count aren’t modelled here: every figure is one economy seat.

Flight emissions

Questions about the carbon footprint of flying

It depends mostly on distance. On this calculator's method, an economy seat costs about 148 g CO₂e per kilometre on short-haul and 142 g on long-haul, including non-CO₂ warming and fuel production. London to New York one way comes to roughly 785 kg.

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