Offsetting a flight means paying for one tonne of CO₂e to be reduced or removed elsewhere for each tonne your trip emits, and making sure those credits are retired. The steps are simple; the harder part is getting the estimate right and choosing credits you can check. This page is part of our guide to offsetting.
How much CO₂ does a flight emit?
A flight’s footprint depends on how far you fly, the type of flight and where you sit. Our flight emissions calculator multiplies the distance between the two airports by UK government factors in kg CO₂e per passenger-kilometreSource 2. Those factors already include an allowance for indirect routes and circlingSource 3.
As an example, a return economy flight from London Heathrow to New York JFK comes to about 1.30 t CO₂e per passenger, including non-CO₂ effects. The calculator page shows the arithmetic step by step.
Cabin class makes a big difference. DESNZ’s long-haul business-class factor is almost three times its economy factor, because premium seats take up more room on the aircraftSource 2.
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Buy portfolio credits
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Short flights and long flights
Per kilometre, short flights are the least efficient. Take-off needs much more energy than cruising, and on a short trip that extra fuel is spread over fewer kilometres. Our World in Data notes that domestic flights have higher emissions per passenger-kilometre than short-haul international flights, and long-haul flights slightly lower againSource 4.
The UK government’s factors show the same pattern. For an average passenger with non-CO₂ effects, the domestic factor is about one and a half times the long-haul factor per kilometreSource 2. A long-haul trip still has the bigger footprint overall because of the distance, but a short flight is where a train can make the biggest difference for each kilometre travelled.
Flying for work? Our guide to offsetting business travel covers cabin-class policies and reporting. If you fly several times a year, add up each trip in the calculator, or use our carbon footprint calculator, which counts return flights by type alongside the rest of your footprint.
Non-CO₂ effects
Aircraft warm the climate through more than CO₂, for example through contrails and nitrogen oxides at altitude. The UK government recommends a multiplier of 1.7 on the CO₂ part of aviation emissions as a central estimate, and notes that the value is very uncertainSource 3. Our calculator includes these effects by default, and you can switch them off to compare. Offsetting the higher figure covers more of a flight’s likely effect.
Cut what you can first
The Oxford Offsetting Principles start with reducing your own emissions and treat credits as a complement for what remainsSource 5. For flights, that means:
- Take the train where you can. Our World in Data puts a domestic flight at about 246 grams of CO₂e per passenger-kilometre, against about 35 grams for national rail. It estimates that taking the train instead of a domestic flight cuts that journey’s emissions by around 86%Source 4.
- Fly economy. The same trip in economy has a much smaller share of the aircraft’s emissions than business or first classSource 2.
- Take fewer, longer trips rather than several short ones, and combine journeys where you can.
How to offset a flight, step by step
Step 1: Estimate the flight’s emissions
Use a flight calculator with your airports, cabin class and trip type to get tonnes of CO₂e per passenger.
Step 2: Cut what you can
Consider whether the trip is needed, whether a train could replace it, and flying economy.
Step 3: Work out how many credits you need
One credit covers one tonne of CO₂e, so round your estimate up to whole credits.
Step 4: Choose the credits
Pick a project type and standard, and decide whether you want removal credits, avoidance credits or a mix.
Step 5: Buy from a seller you can check
Choose a seller that names the project, standard and registry before you pay.
Step 6: Confirm the retirement
Look up the serial numbers in the public registry and check the quantity and your name.
One credit represents one tonne of CO₂eSource 8, so a flight of a little over one tonne needs two credits to be covered in full. Our credits calculator rounds up for you and shows an estimated cost.
Which credits suit a flight?
Flights are hard to decarbonise quickly, so many travellers look at what kind of credit they buy. Avoidance credits pay for emissions that would otherwise have happened; removal credits pay for CO₂ taken out of the atmosphere and stored. The Oxford Principles recommend shifting toward removals with a low risk of reversal over timeSource 5.
Removals cost more. In 2024, removal credits sold for an average of $19.50 per tonne, against $4.05 for reduction creditsSource 6. A mix of the two is a common compromise. Our page on removal vs avoidance credits explains the trade-offs, and the carbon credit price page shows the latest averages by type.
Airlines have their own scheme. Under the Carbon Offsetting and Reduction Scheme for International Aviation (CORSIA), aeroplane operators monitor and report emissions from international flights and buy and cancel eligible emission units to meet an offsetting obligationSource 1. Our CORSIA guide explains how it works and whether it matters when you offset a personal flight.
Be careful with “offset your flight” offers
Claims: what an offset can and can't say
US guidance on environmental marketing uses a flight as its example. An offer to “neutralize the carbon emissions from your flight” is misleading if the projects it funds won’t reduce emissions for two years or more, unless that is clearly disclosedSource 7. Before you buy, check when the reductions happen and whether the credits are already issued and retired.
Flying to a wedding or conference? See offsetting a wedding or event. For everyday emissions beyond flying, our guide to buying carbon credits as an individual covers the whole process, and how to verify carbon credits shows how to check a retirement.