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Carbon · Comparison

Flight vs Train CO₂

Estimate CO₂e per passenger for one trip by flight, national rail, coach or car. Enter the flight distance and the rail or road distance separately — they are rarely the same.

Airport to airport, straight line. The factors already add 8% for indirect routing.

Used for rail, coach and car. Usually longer than the flight distance.

Distance unit
Trip

UK source bands: domestic = within the UK, short-haul = UK–Europe, long-haul = UK–outside Europe.

Car emissions are shared between everyone in it.

CO₂e per passenger for this trip

Return trip — each one-way distance counted twice. Listed in a fixed order, not ranked.

Flight — Short-haul, to/from UK, average passenger, incl. non-CO₂ effects256 kg CO₂e

2,000 km × 0.12786 kg CO₂e per passenger-km

National rail (UK average)70.9 kg CO₂e

2,000 km × 0.03546 kg CO₂e per passenger-km

Coach (UK average)55.5 kg CO₂e

2,000 km × 0.02776 kg CO₂e per passenger-km

Car, petrol (UK average car)325 kg CO₂e

2,000 km × 0.16272 kg CO₂e per vehicle-km

Car, diesel (UK average car)346 kg CO₂e

2,000 km × 0.17304 kg CO₂e per vehicle-km

Car, battery electric (UK average car)80.9 kg CO₂e

2,000 km × 0.04047 kg CO₂e per vehicle-km

Formula and factors

Trip distance = one-way distance × (2 if return, else 1)

Flight, rail, coach: CO₂e per passenger = trip distance × factor per passenger-km

Car: CO₂e per passenger = trip distance × factor per vehicle-km ÷ people in the car

Modekg CO₂ePer
Flight — Short-haul, to/from UK (with non-CO₂ effects)0.12786passenger-km
National rail (UK average)0.03546passenger-km
Coach (UK average)0.02776passenger-km
Car, petrol (UK average car)0.16272vehicle-km
Car, diesel (UK average car)0.17304vehicle-km
Car, battery electric (UK average car)0.04047vehicle-km

Source: UK Government GHG Conversion Factors for Company Reporting 2025 (DESNZ), flat-format file. Average passenger flight factors and UK average rail, coach and cars. Well-to-tank (fuel supply) emissions are excluded for every mode; the electric-car factor covers UK electricity generation plus grid losses. Factors for other countries' trains, coaches and grids can be very different, so treat results as UK-average estimates. Sources and methodology. For a whole year of travel and home energy, the carbon footprint guide explains how trips fit into a household total.

FAQ

Where do the factors come from?
Every factor is a kg CO₂e row from the UK Government GHG Conversion Factors for Company Reporting 2025 (DESNZ): flights from "Business travel- air", rail, coach and cars from "Business travel- land". They describe average UK vehicles and services, and flights to, from or outside the UK. Other countries' trains, coaches and grids can differ.
What does "include non-CO₂ effects" do?
The UK factors for flights are published in two versions. The higher version adds an estimate of the extra warming from non-CO₂ effects at altitude (contrails, water vapour, NOx), which the source applies as a 70% increase on the CO₂ part of the factor. The source recommends using it but notes significant scientific uncertainty about its size. The toggle lets you see both.
Why are there two distances?
Planes, trains and cars rarely travel the same distance between two cities. Enter the airport-to-airport (straight-line) distance for the flight: the UK flight factors already include an 8% uplift for indirect routing and holding. Enter the rail or road distance for ground travel. If you only know one distance, the comparison is approximate.
How is a shared car handled?
Car factors are per vehicle-km, so the car's emissions are divided by the number of people in it. Rail and coach factors are already per passenger-km and are not divided again.
Is this a lifecycle comparison?
No. Petrol, diesel, rail, coach and flight factors cover emissions from operating the vehicle (fuel burned, or the electricity used by the service) and exclude the separately published well-to-tank (fuel supply) factors. The electric-car factor covers UK electricity generation plus grid losses. Vehicle, track and airport construction are not included.

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