National rail emission factor 2026 (UK, kg CO2e per passenger km)

The 2026 UK government emission factor for national rail is 0.030920 kg CO2e per passenger km, reported as Scope 3, category 6 (business travel). That is 12.8% lower than the 2025 factor of 0.035460. Including well-to-tank, the full figure is 0.039890 kg CO2e per passenger km.

Updated 3 October 2026 by the Carbon Recycling team. Figures use the official UK government conversion factors and are checked against the current gov.uk guidance.

National rail emission factor by year

Year	Scope 3 (kg CO2e per passenger km)	Well-to-tank	Full figure	Change
2026	0.030920	0.008970	0.039890	-12.8%
2025	0.035460	0.008970	0.044430	0.0%
2024	0.035460	0.008970	0.044430	-0.0%
2023	0.035463	0.008966	0.044429	-0.1%
2022	0.035490	0.008920	0.044410	0.0%
2021	0.035490	0.008850	0.044340	-3.9%
2020	0.036940	0.007240	0.044180	-10.2%
2019	0.041150	0.007900	0.049050	–

Total kg CO2e for the seven greenhouse gases, from the official DESNZ files for each year. 2026 factor ID: 25_315_3147_11_1. Where a factor jumps sharply between two years, it is usually because DESNZ changed its method or data source, not because the activity itself changed.

Worked example

Take staff travelling 30,000 passenger km by train a year. 30,000 passenger km × 0.030920 kg CO2e = 0.93 tonnes CO2e, reported as Scope 3, category 6 (business travel). Adding well-to-tank brings the full figure to 1.20 tonnes CO2e; the extra 0.27 tonnes are Scope 3 category 3.

How to report it

Train travel on business is Scope 3 category 6; commuting by train is category 7. The factor is the same.

Rail is one of the lowest-carbon ways to travel, so moving domestic flights and long car journeys onto trains is a common, easy reduction to put in a Carbon Reduction Plan.

Where the data comes from

You'll usually find it in rail bookings or expenses, converted to distance. Keep the source documents: anyone checking your Carbon Reduction Plan or SECR report may ask how each figure was worked out.

Read more about how the factors change each year in our guide to the 2026 conversion factors, or see how we apply them in our methodology.

Related emission factors

Domestic flights: 0.22928 kg CO2e per passenger km
Average diesel car: 0.27786 kg CO2e per mile
Average local bus: 0.10151 kg CO2e per passenger km
All UK emission factors

Frequently asked questions

Which year's factor should I use?

The set for the year your reporting period falls in. If your financial year spans two calendar years, use the set for the calendar year most of it falls in, and keep the same rule every year. Don't restate past years with new factors unless you are correcting an error.

Is this the DEFRA factor?

Yes. The UK government conversion factors used to be published by DEFRA, then BEIS, and since 2023 by the Department for Energy Security and Net Zero (DESNZ). Many people still call them the DEFRA factors.

Do I need to include well-to-tank emissions?

They are Scope 3 category 3 (fuel- and energy-related activities). SECR doesn't require them, and PPN 006 doesn't list category 3 among its required Scope 3 categories, but including them gives a more complete footprint and some customers ask for them.

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