How much CO2 does a flight emit per passenger?

With the DESNZ 2026 factors including radiative forcing, about 0.11–0.13 kg CO2e per km for an economy seat on international routes and 0.23 kg per km on UK domestic flights, which are short and less efficient per km. London to New York (about 5,540 km) is roughly 650 kg CO2e one-way in economy, 1.9 t in business and 2.6 t in first.

What is radiative forcing and should I include it?

Aircraft also warm the climate through contrails, contrail cirrus and nitrogen oxides at altitude. DESNZ recommends a 1.7 multiplier on the CO2 part as a central estimate (from Lee et al., 2021) while noting the large uncertainty, and publishes factors with and without it. Including it gives a fuller picture of climate impact; excluding it matches CO2-only inventories.

Why does business class have a higher footprint?

Emissions are shared out by the floor space each cabin takes up. Business seats are much larger, so DESNZ allocates a long-haul business seat 2.9 times the emissions of an economy seat (0.339 vs 0.117 kg CO2e per km with RF); first class is 4 times economy.

Do I need to add extra distance for routing?

No. DESNZ adds 8% to great-circle distances for indirect routes, holding and delays and builds that uplift into the factors, so enter or use the great-circle distance. Other calculators use different rules (for example a fixed 95 km added per flight), which is one reason their results differ.

What are well-to-tank emissions?

They are the emissions from extracting, refining and transporting the jet fuel before it is burned, reported as a separate Scope 3 category. For a long-haul economy seat DESNZ gives 0.0246 kg CO2e per km, about 21% on top of the flight factor with RF.

Is a connecting flight worse than a direct one?

Usually yes: the route is longer and each extra take-off and climb burns more fuel per km. Add the connection airport to compare. Very long nonstop flights carry extra fuel weight, but DESNZ factors do not vary within a haul, so the calculator reflects the distance effect only.

Flight Carbon Calculator

Pick your airports (or enter a distance), class and options. London Heathrow to New York JFK one-way in economy is about 5,540 km and 648 kg CO2e per passenger with radiative forcing (384 kg without), using the DESNZ 2026 factors.

Flight Parameters

Airports Distance

From

Connection (optional)

Flight Type

DESNZ uses route regions, not a distance-only 3,700 km cutoff.

Seating Class

Journey Type One-way flight

Radiative Forcing (RF) Includes non-CO2 high-altitude warming

Well-to-tank fuel emissions Not included

Number of Passengers

Awaiting Flight Parameters

Choose airports or a distance, a seating class and options, then calculate.

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Summary

This calculator multiplies the great-circle distance of each flight leg by the UK Department for Energy Security and Net Zero (DESNZ) 2026 greenhouse gas conversion factors, the dataset most companies use for Scope 3 business travel. Factors depend on the haul (domestic UK, short-haul between the UK and Europe or North Africa, long-haul, or international between non-UK airports), on the seating class, whose floor space determines its share of the fuel, and on whether non-CO2 effects at altitude are included through radiative forcing (RF). DESNZ already builds an 8% uplift for indirect routing and holding into the factors, so the great-circle distance is used as is. Well-to-tank emissions from producing and delivering the jet fuel can be added on top.

How it works

Choose airports (with an optional connection) or enter a one-way distance. Airport distances are great-circle distances from the airport coordinates (haversine, Earth radius 6,371 km).
Each leg is classified as DESNZ does: both airports in the UK = domestic; UK to Europe (including Turkey and Greenland, excluding Ukraine and Moldova) or North Africa = short-haul; UK to anywhere else = long-haul; no UK airport = international.
Emissions per passenger = distance × factor (kg CO2e per passenger-km) for the class. If DESNZ has no factor for a class on that haul (premium economy or first on short-haul), the average-passenger factor is used and flagged.
Radiative forcing multiplies the CO2 part by 1.7 as DESNZ recommends; well-to-tank adds the fuel supply chain. Round trips double the result; passengers multiply it.

Use cases

Report Scope 3 business travel emissions with the same DESNZ factors auditors expect.
Compare economy and business class, or a direct flight and a connection.
Show the effect of including radiative forcing and well-to-tank emissions.
Estimate the footprint of a group trip or conference travel.

Frequently Asked Questions

Last updated: 2026-10-10 · Reviewed by Nham Vu

Flight Carbon Calculator

Flight Parameters

Awaiting Flight Parameters

Per-passenger breakdown

Calculation Audit DESNZ 2026 factors

Seating Class Comparison

Summary

How it works

Use cases

Frequently Asked Questions

Flight Carbon Calculator

Use the Flight Carbon Calculator

Flight Parameters

Awaiting Flight Parameters

Per-passenger breakdown

Calculation Audit DESNZ 2026 factors

Seating Class Comparison

Summary

How it works

Use cases

Frequently Asked Questions