Flight Carbon Footprint Calculator
Calculate the CO2-equivalent emissions of any flight by distance, seat class, number of travellers, and trip type. Toggle radiative forcing, add an optional offset cost estimate, and see how your journey compares to driving.
Formula
Worked example
A 1,000 km one-way economy flight (short haul, factor 0.158 kg/km with RF): 1000 x 1 x 0.158 = 158 kg CO2e per passenger. Two passengers round-trip: 158 x 2 x 2 = 632 kg total.
How the emission factors are calculated
Every flight produces CO2 from burning jet fuel, but the warming effect at altitude is greater than CO2 alone. Contrail cirrus clouds, ozone production from nitrogen oxides, and water vapour released at cruise altitude all trap additional heat. The UK Department for Energy Security and Net Zero (DESNZ, formerly DEFRA) publishes annual GHG conversion factors that combine the direct combustion CO2 with a radiative forcing (RF) multiplier of approximately 1.9. This calculator uses those 2024 DEFRA factors, banded by route length into short haul (under 1,500 km), medium haul (1,500-3,700 km), and long haul (3,700 km and above). If you need the CO2-only figure for Scope 1 corporate reporting, toggle radiative forcing off.
Why cabin class changes your footprint so much
Airlines allocate the total fuel burn of a flight among passengers in proportion to the floor area each seat occupies. An economy seat takes up the smallest footprint, so economy passengers are allocated the least CO2. A premium economy seat is roughly 1.6 times wider or pitched further apart, translating to a factor about 1.6 times higher. A business-class flat bed can occupy two to three times the floor area of an economy seat, pushing its factor to around 2.2-2.9 times higher. First-class suites on some widebody aircraft take up four times the space, making the footprint four times larger for the same journey. This methodology follows the DEFRA area-based approach and is used by most leading carbon accounting standards.
Offset cost and what it means
Turning on the offset cost estimate converts your total CO2e into metric tonnes and multiplies by a price per tonne. Prices for verified carbon offsets range from roughly $10 per tonne for the cheapest commodity credits to over $50 per tonne for Gold Standard or Verra VCS certified projects with strong co-benefits. The default of $15 per tonne is a common retail starting point. Buying an offset does not undo the warming already caused by your flight, but it directs money into verified projects that reduce or remove greenhouse gases elsewhere. Many airlines now offer in-booking offsets at similar price points.
Comparing flight emissions to other activities
The calculator converts total CO2e into equivalent driving distance using the UK DEFRA 2024 figure of 0.171 kg CO2e per km for an average petrol car. A 1,000 km economy flight emits about 158 kg CO2e, which is the same as driving roughly 924 km. A transatlantic economy flight of 5,500 km emits around 814 kg CO2e, about the same as 4,760 km of driving. The tree equivalence uses 21 kg of CO2 absorbed per mature broadleaf tree per year, a widely cited average from the Woodland Trust. These comparisons are rough guides: actual car emissions depend on vehicle type and fuel, and tree absorption rates vary with species, age, and soil conditions.
Economy-class emission factors by route length
| Haul type | Distance band | Economy | Premium economy | Business | First |
|---|---|---|---|---|---|
| Short haul | Under 1,500 km | 0.158 | 0.253 | 0.349 | 0.632 |
| Medium haul | 1,500-3,700 km | 0.131 | 0.210 | 0.289 | 0.524 |
| Long haul | 3,700 km and over | 0.148 | 0.237 | 0.429 | 0.592 |
Factors include radiative forcing (RF multiplier 1.9). Source: UK DESNZ/DEFRA GHG Conversion Factors 2024.
Frequently asked questions
What is the carbon footprint of a flight per kilometre?
In economy class with radiative forcing included, typical DEFRA 2024 figures are 0.158 kg CO2e per passenger-km for short haul (under 1,500 km), 0.131 for medium haul (1,500-3,700 km), and 0.148 for long haul (over 3,700 km). Without radiative forcing the figures are about 1.9 times lower. Business class is roughly 2.2-2.9 times higher than economy and first class is about four times higher.
Does flying business class really increase my carbon footprint?
Yes, significantly. DEFRA allocates emissions in proportion to the floor area each seat occupies relative to an economy seat. A business-class flat bed typically occupies two to three times the space, so its allocated CO2e is roughly 2.2-2.9 times higher than the same journey in economy. First-class suites can be four times larger, producing four times the footprint. Choosing economy on the same aircraft and route is the single biggest per-journey reduction a traveller can make.
What is radiative forcing and why does it matter?
Radiative forcing describes the additional warming caused by aviation beyond the CO2 from burning jet fuel. At cruise altitude, aircraft release water vapour that forms contrail cirrus clouds, produce nitrogen oxides that create ozone, and emit particulates, all of which trap heat. The IPCC and researchers at Deutsches Zentrum fuer Luft- und Raumfahrt (DLR) estimate the effective climate impact of aviation is roughly 1.7 to 4 times greater than the CO2 figure alone. DEFRA uses an RF factor of approximately 1.9 in its passenger emission factors. Toggle radiative forcing off if you need the CO2-only figure for a GHG Protocol Scope 1 or Scope 3 inventory.
How do I calculate emissions for a connecting flight?
Enter each leg separately and sum the results. A connecting flight increases total distance and adds an extra takeoff and climb, both of which burn more fuel per km than cruise. The haul-band factor may also change between legs: a short domestic hop connecting to a long international flight carries a higher per-km factor than the long-haul segment alone.
How many trees does it take to offset a flight?
This calculator uses 21 kg of CO2 absorbed per mature broadleaf tree per year, a widely cited average from the Woodland Trust. A 1,000 km one-way economy flight emits about 158 kg CO2e, requiring roughly 8 trees for one year. A long-haul economy flight of 5,500 km emits around 814 kg CO2e, equivalent to 39 trees for a year. Young trees absorb much less than mature ones, so planting programmes need to account for years of growth before full absorption is reached.
How much does a carbon offset for a flight cost?
Verified carbon offset prices vary by project type and certification standard. Basic credits on commodity markets can be as low as $5-10 per tonne of CO2e, while Gold Standard or Verra VCS certified projects with strong social co-benefits typically cost $15-50 per tonne or more. Turn on "Estimate offset cost" in this calculator and enter a price to see the total for your trip. Many airline booking platforms offer in-flight offset options at similar price points.