How to Calculate Business Travel Emissions (Flights, Rail, Hotels)

Why Business Travel Emissions Are Hard to Get Right

Business travel sits in Scope 3 Category 6 and is the most underestimated category for professional services firms, consultancies, financial services companies, and any business with regular site visits, client meetings, or international trips.

The challenge is data: unlike gas or electricity, travel emissions don't appear on a single bill. They are scattered across expense reports, booking platforms, corporate travel agencies, and personal reimbursement claims. This guide explains exactly how to find and calculate every category.

What DEFRA 2023 Emission Factors Apply to Business Flights?

Flight emissions depend on three variables: distance band, cabin class, and whether you include radiative forcing (RF). The GHG Protocol and most procurement questionnaires accept DEFRA factors with RF included — they capture the warming effect of contrails and other non-CO2 aviation impacts at altitude.

Short-haul flights (under 3,700 km — most European routes):

Long-haul flights (3,700+ km — intercontinental):

For flight distances, use the great-circle distance (direct route between airports). London Heathrow to Frankfurt = 630 km. London to New York JFK = 5,540 km.

Worked example — return business class flight, London–Berlin (932 km each way): 932 × 2 (return) × 0.511 ÷ 1,000 = 0.953 tCO2e per person

How Do You Calculate Rail Travel Emissions?

Rail is significantly lower-carbon than air for equivalent distances.

Worked example — London to Edinburgh return by rail (1,268 km total): 1,268 × 0.035 ÷ 1,000 = 0.044 tCO2e — versus 0.477 tCO2e for a short-haul economy flight covering the same distance.

How Do You Calculate Car Travel Emissions?

For company car journeys or employee-reimbursed mileage:

HMRC mileage records (submitted for reimbursement claims) are the most reliable source of annual company car mileage data. Many businesses also find this data in expense management systems like Concur, Expensify, or Rydoo.

How Do You Account for Hotel Stays?

Hotel stays are a Scope 3 Category 6 emissions source. The DEFRA 2023 factor is:

Worked example — 40 room-nights per year: 40 × 0.074 = 2.96 kgCO2e — a small but reportable amount.

Hotel stays are typically minor compared to flights and car mileage, but should be included for completeness, especially on questionnaires that ask explicitly about accommodation.

How Do You Find Business Travel Data Without a Central Travel System?

Most SMEs do not have a corporate travel management system. Practical approaches:

• Expense reports — most accounting software (Xero, QuickBooks, Sage) has a travel or mileage category. Export the annual total.
• HMRC mileage records — if you reimburse at HMRC rates, you have the km data.
• Corporate credit card statements — airline, rail, and hotel bookings are identifiable categories.
• Personal reimbursements — circulate a brief survey asking employees to estimate their annual business travel by mode. A 10-minute survey across a 20-person team gives you usable data.

For your first Carbon Passport, reasonable estimates with a documented methodology are accepted. DeCarbonOPS guides you through this category and records your assumptions so any future auditor can follow the logic.

What Is the Highest-Impact Travel Reduction Action?

Substituting one return transatlantic flight (economy) per person with video conferencing saves approximately 2.0–2.5 tCO2e per trip. For a team of 10 that each makes two transatlantic trips per year, eliminating those trips saves 40–50 tCO2e — more than most SME offices' entire Scope 2 electricity footprint. A travel policy requiring rail for European journeys under 4 hours is also standard practice for net-zero-committed businesses.

Generate a Carbon Passport to calculate your exact travel footprint as part of your full Scope 3 baseline.