Business travel emissions: trains, flights and mileage

To calculate business travel emissions, multiply the distance of each journey by the UK government conversion factor for that mode of transport, then add them up. In the 2026 factors, a train is roughly 0.031 kg CO2e per passenger kilometre, a domestic flight roughly 0.229 kg, and an average petrol car roughly 0.26 kg per mile. One return economy flight from London to New York comes to around 1.3 tonnes, about the same as 10,000 kWh of grid electricity at the 2026 factor.

Business travel is often the most variable part of a small firm’s footprint. It’s also where one decision, train or plane, changes the numbers most.

What counts as business travel emissions?

Business travel is part of Scope 3, category 6 in the GHG Protocol. It covers work journeys in vehicles your business doesn’t own or control:

• Flights
• Trains, including the Underground and trams
• Taxis and ride-hailing
• Employees’ own cars used for work and paid through mileage claims, often called grey fleet
• Hire cars and buses
• Hotel stays, which the GHG Protocol lists as optional

Two things don’t belong here. Vehicles the company owns or leases are Scope 1, not business travel. And the daily journey to work is commuting, which is a separate category.

How do you calculate flight emissions?

You need three things: the distance, the type of flight and the seating class.

• Distance. Use the great circle distance between airports. The UK factors already include an 8% uplift for indirect routes and holding patterns, so don’t add your own.
• Flight type. The factors split into domestic (within the UK), short-haul (broadly, flights between the UK and Europe) and long-haul (everything further).
• Class. Premium seats take more cabin space, so they carry more emissions per passenger.

Always use the factors with radiative forcing. These account for the extra warming caused by emissions released at altitude, and they’re what buyers and frameworks expect to see.

If you don’t know the exact routes, the 2026 government methodology publishes average one-way distances: about 434 km for domestic, 1,484 km for short-haul and 6,799 km for long-haul. The ESG Now questionnaire uses these when you give it a count of return flights.

Approximate 2026 factors for business travel

These are rounded from the 2026 UK government conversion factors and are approximate. Use the full spreadsheet for exact values.

Mode	Approximate factor
National rail	0.031 kg per passenger km
Domestic flight (average)	0.229 kg per passenger km
Short-haul flight, economy	0.126 kg per passenger km
Short-haul flight, business	0.189 kg per passenger km
Long-haul flight, economy	0.117 kg per passenger km
Long-haul flight, business	0.339 kg per passenger km
Average petrol car	0.26 kg per mile
Average diesel car	0.28 kg per mile
Regular taxi	0.149 kg per passenger km
Black cab	0.204 kg per passenger km
UK hotel stay	10.4 kg per room per night
London hotel stay	11.5 kg per room per night

Long-haul economy looks lower per kilometre than short-haul. That’s because take-off and climb use a lot of fuel, so short flights have a higher share per kilometre. The total for a long-haul trip is still far higher because of the distance.

How do you calculate mileage claims, taxis and hotels?

The ESG Now questionnaire estimates these for you from mileage claims, taxi miles and hotel nights. Here’s the method, if you want to understand or check the figures.

Mileage claims. Your expenses system already holds the miles. Total them for the year and multiply by the per-mile factor. If you don’t know the car types, the spreadsheet has average car factors for an unknown fuel type that work as a default. If someone drives an electric car on a mileage claim, the per-mile figure is much lower, so use the battery electric factor from the spreadsheet for those journeys.

Taxis. If you have distances, multiply by about 0.149 kg per passenger kilometre. If you only have receipts, estimate an average journey length and multiply by the number of trips. Black cabs are higher, at about 0.204 kg, so use that figure for those journeys.

Hotels. Count the room nights and multiply by the factor for the country. A UK hotel stay is about 10.4 kg per room per night, and London is 11.5 kg. The spreadsheet gives figures for many other countries too.

If you work these out by hand, label them as estimates and note the method in a sentence.

A worked example: a consultancy’s year of travel

A nine-person management consultancy has no company vehicles. In a year, the team took 30 return train trips between London and Birmingham, two return economy flights to New York, claimed 6,000 miles in their own cars, took about 400 km of taxi journeys and stayed 25 nights in UK hotels outside London.

Using the approximate factors above:

Journey	Calculation	Emissions
Rail	30 returns × 2 × about 182 km = 10,920 km × 0.031	0.34 t
Flights	2 returns × 2 × about 5,570 km = 22,280 km × 0.117	2.61 t
Mileage claims	6,000 miles × 0.26	1.56 t
Taxis	400 km × 0.149	0.06 t
Hotels	25 nights × 10.4 kg	0.26 t
Total		about 4.8 tCO2e

Two transatlantic flights account for more than half of the travel footprint. Thirty train trips, by contrast, barely register. If one of those New York trips had been in business class, the flight line alone would have risen by around 2.5 tonnes.

The ESG Now report would calculate every line here: rail and flights from trip counts or distances, and mileage, taxis and hotels from claimed miles, taxi miles and room nights.

How can you cut business travel emissions?

Without telling anyone to stop seeing clients:

• Make rail the default for UK trips where the journey time is reasonable.
• Fly economy on long-haul unless there’s a real need for a premium seat.
• Combine trips. One longer visit instead of two short ones.
• Keep records. Origin, destination and class for each flight, and miles from expense claims. Next year’s figures will be measured, not estimated.

What does the ESG Now footprint include?

The ESG Now questionnaire covers business travel by air and rail, including seating class and radiative forcing for flights, plus mileage claims by fuel type, taxis and hotel nights in the UK, London or overseas. It also covers heating, company vehicles, electricity, EV charging, water and waste, and estimates commuting and homeworking. Our guide to working-from-home emissions explains how the homeworking estimate works.

Most small businesses finish in under 30 minutes, and every figure in the report shows its working. Start your free report, or read our carbon footprint guide for the full picture and our small businesses page for what you get.