How to Calculate the Carbon Footprint of Company Vehicles

In many companies, sales teams, service vehicles, light commercial vehicles and executive cars are the largest Scope 1 item after natural gas. In service companies, they are often almost the whole of Scope 1. The good news: because most fleets in Türkiye run on fuel cards, the data you need is already sitting somewhere. This guide explains how to split that data into the right scopes and convert it into tCO₂e.

Which scope do vehicle emissions fall under?

The GHG Protocol Corporate Standard defines emissions from burning fuel in vehicles that the company owns or controls as direct emissions, i.e. Scope 1 (Chapter 4, pp. 25-27). This is called "mobile combustion". The real question is which vehicles count as "controlled" vehicles.

Leased vehicles: lease type and control approach

In Türkiye, a large share of company fleets is used under long-term operating leases. Appendix A of the Scope 3 Standard resolves this according to the lease type and the organisational boundary approach the company has chosen (Table A.1, p. 124):

A company that chooses the operational control approach reports the fuel of the vehicles it leases in Scope 1. The standard also allows a company that can demonstrate it has no operational control over an asset under an operating lease to report these emissions in Scope 3; but this decision must be disclosed and justified in the report. A company that leases vehicles out to other companies, as a rule, reports the vehicles it leases out in Scope 3 Category 13 (downstream leased assets) (Table A.2, p. 125). Confirm the lease type with your accounting department. For the effect of the control approach choice on the whole inventory, see the organizational and operational boundaries guide.

Vehicles not under the company's control

• Business travel in an employee's own car and hire cars (daily rental): Scope 3 Category 6, business travel (Scope 3 Standard, p. 46).
• Employees' commuting from home to work: Scope 3 Category 7, employee commuting.
• Carriers transporting products and materials: Scope 3 Category 4 or 9. For details, see our Scope 3 logistics post.

Two methods: fuel-based and distance-based

Fuel-based: Emissions (kg CO₂e) = Fuel (litres) × Emission factor (kg CO₂e/litre)

Distance-based: Emissions (kg CO₂e) = Distance (km) × Emission factor by vehicle type (kg CO₂e/km)

The GHG Protocol's Scope 3 calculation guidance states that for CO₂ the fuel-based method is more accurate than the distance-based method, because fuel consumption is directly related to emissions (Category 4, p. 52). The same logic applies to a company fleet. Use the distance-based method only for vehicles without fuel data, or as a cross-check.

Where does the data come from?

Getting the fuel card report by licence plate does two jobs: you can split scopes by lease type, and you can easily catch inconsistencies (for example, petrol bought for a diesel vehicle).

Emission factors: diesel and petrol

While preparing this guide, we could not find an official, litre-based set of vehicle fuel factors for Türkiye that includes CH₄ and N₂O. For this reason, companies generally use the UK government's (DESNZ) annual conversion factors or IPCC defaults. The DESNZ 2026 set gives CO₂e per litre including CH₄ and N₂O and uses AR5 GWP values for fuels.

Which row should you choose? In Türkiye, blending at least 0.5 percent (by volume) of domestic biodiesel into diesel is mandatory (Communiqué on Blending Biodiesel into Diesel Types, Article 5). Because this share is low, the "100 percent mineral diesel" row is a closer proxy for Türkiye; the UK average blend row assumes a higher bio share. Petrol also has a domestic ethanol blending obligation; under Article 5 of the Communiqué on Blending Ethanol into Petrol Types, as amended on 31 October 2025, the share is at least 1.5 percent (by volume), and different shares applied in past years. This also means a lower bio share than the UK average blend; obtain the share for the relevant year from your supplier. Under the GHG Protocol, biogenic CO₂ from burning the bio component is reported separately, outside the scopes.

Cross-check with the IPCC. The IPCC 2006 defaults are 74,100 kg CO₂/TJ and a net calorific value of 43.0 TJ/Gg for diesel, and 69,300 kg CO₂/TJ and 44.3 TJ/Gg for petrol (Table 3.2.1 and Table 1.2). Converting to litres requires density. From the ratio of the tonne and litre values in the DESNZ table, a density of about 0.83 kg/litre is derived for diesel. With this, the IPCC default gives 2.65 kg CO₂ per litre. The 2022 values in Türkiye's 2024 national inventory document (72.3 t CO₂/TJ and 43.33 TJ/kt for diesel) come to 2.60 kg CO₂/litre with the same density. DESNZ's value of 2.63 kg lies between these two, and the differences are around 1 percent. If you have density and calorific value data from your own supplier, you can also calculate this way.

A note on CH₄ and N₂O. The IPCC stresses that CH₄ and N₂O emissions from vehicles depend largely on engine and emission control technology, and that default values that do not specify technology are highly uncertain. For diesel, these two gases are about 1.3 percent of the total; in large fleets, breaking them down by vehicle technology is therefore mostly a matter of data quality.

Worked example: a 42-vehicle fleet

The vehicle numbers, litres and kilometres below are illustrative values. The company uses the operational control approach. The fleet:

• 25 diesel passenger cars, operating lease
• 8 diesel light commercial vehicles, company-owned
• 5 petrol passenger cars, company-owned
• 4 electric passenger cars, operating lease, charged at head office

2025 fuel card report: diesel 96,000 litres, petrol 9,500 litres. Sub-meter of the charging units at head office: 17,500 kWh.

Diesel (DESNZ 2026, 100 percent mineral): 96,000 L × 2.66155 kg CO₂e/L = 255,508.8 kg = 255.51 tCO₂e (CO₂: 252,305.3 kg; CH₄: 27.8 kg CO₂e; N₂O: 3,175.7 kg CO₂e)

Petrol (DESNZ 2026, 100 percent mineral): 9,500 L × 2.35372 kg CO₂e/L = 22,360.3 kg = 22.36 tCO₂e

Scope 1 total: 255.51 + 22.36 = 277.87 tCO₂e

Electric vehicles, Scope 2 (location-based): 17.5 MWh × 0.434 tCO₂e/MWh = 7.60 tCO₂e The factor is ETKB's (Ministry of Energy and Natural Resources) Türkiye-wide electricity generation value for the 2023 calculation period. We explain why we chose this factor in the electricity consumption guide.

The same fleet under the financial control approach

Had the company chosen the financial control approach, the fuel of the 25 diesel passenger cars under operating leases would move out of Scope 1 and into Scope 3 Category 8. If, according to the licence plate report, these vehicles took 62,000 litres (illustrative value) of diesel:

62,000 L × 2.66155 = 165,016.1 kg = 165.02 tCO₂e moves to Scope 3 Category 8; Scope 1 falls to 112.85 tCO₂e. Total emissions do not change; the distribution between scopes does. That is why you should make the approach choice once, at the very start, for the whole inventory.

Distance-based cross-check

Suppose the same 25 diesel passenger cars each drove an average of 32,000 km a year (illustrative value). With the DESNZ 2026 average diesel car factor:

800,000 km × 0.17265 kg CO₂e/km = 138,120 kg = 138.12 tCO₂e

The fuel-based result is 165.02 tCO₂e; the distance-based calculation is about 16 percent lower. The actual consumption of the vehicles in the example is 62,000 ÷ 800,000 = 7.75 litres/100 km. The kilometre factor, by contrast, reflects the consumption of the average car fleet in the UK. The difference shows why the distance-based method is only a last resort. DESNZ 2026 also gives kilometre factors for other vehicle types: average petrol car 0.16152, average hybrid car 0.12961, average diesel van up to 3.5 tonnes 0.25716 kg CO₂e/km.

Electric and hybrid vehicles

• Battery electric vehicles: There are no tailpipe emissions, and nothing is recorded in Scope 1. Charging electricity is Scope 2 for vehicles under the company's control. DESNZ also classifies electric vehicle charging under Scope 2.
• If there is no charging data: An estimate can be made from kilometres. DESNZ 2026 gives 0.20358 kWh/km for the UK average electric car. For example, 80,000 km × 0.20358 = 16,286 kWh; with the Türkiye factor, this means 16.29 MWh × 0.434 = 7.07 tCO₂e. This is an approximation; measured kWh is always preferable.
• Where does charging take place? If the electricity for a charging unit at a company site is already included in the building's invoice, do not add it again; just separate it with a sub-meter and show it in the report. Total the electricity bought from external charging networks from their invoices.
• Plug-in hybrids: Petrol on the fuel card is Scope 1, and charging electricity is Scope 2. Total them separately.

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Common mistakes

1. Leaving leased vehicles out of the inventory. Skipping vehicles under operating leases because "the car isn't ours" leaves Scope 1 incomplete under the operational control approach.
2. Classification that contradicts the control approach. Reporting buildings under financial control and vehicles under operational control is inconsistent. There is one approach for the whole inventory.
3. Working back from spend to litres. Dividing fuel spend by the average pump price to get litres carries a large margin of error. Take litres directly from the fuel card report.
4. Using the UK blend factor without question. The biodiesel share in diesel in Türkiye is lower than the UK average; the blend row can understate emissions.
5. Counting electric vehicles as zero. Tailpipe emissions are zero, but charging electricity falls under Scope 2.
6. Counting charging electricity twice. Adding charging consumption separately when it already passes through the building meter.
7. Recording business travel in Scope 1. Employees' own cars and daily hire cars are Category 6.
8. Missing vehicles that joined and left the fleet during the year. The fuel card report should be taken by licence plate and for the full year; cards for vehicles returned during the year should also be included.

Next step

Fleet emissions are one of the areas where reductions deliver the fastest results: vehicle selection policy, the switch to electric vehicles and route optimisation feed directly into Scope 1. For the rest of the inventory, go back to the carbon footprint calculation guide and the natural gas emissions calculation guide, and to rank abatement measures, continue with the abatement measures and MACC guide. If you want to turn your fleet data into a verification-ready inventory, Alalëa's carbon footprint service takes this work from data collection to reporting together with you.