Scope 3 for SME Suppliers:
the essential 2026 guide.

Scope 3 for SME suppliers is now at the heart of large accounts’ carbon requirements. Your clients subject to CSRD need your data to complete their own carbon footprint — here’s exactly what that means and how to measure it.

Scope 3 for SME suppliers: the three emissions categories

The GHG Protocol, the international carbon accounting standard used by nearly all large companies, divides emissions into three categories called “Scopes.” Picture a furniture manufacturing plant.

• Scope 1: direct emissions. Gas for heating the workshops, diesel for forklifts, company-owned vehicles. Controlled sources, accessible data. Detailed Scope 1 guide →
• Scope 2: energy purchased externally. Mainly electricity. In France, thanks to nuclear power, this item is generally low. Detailed Scope 2 guide →
• Scope 3: everything else. Wood purchased from sawmills, transport by service providers, employee travel, packaging, machinery. And at the other end: delivery to customers, product use, and end of life.

For most industrial and commercial companies, Scope 3 accounts for between 70% and 95% of total emissions. That’s why your client cares about it, and why they need your data to complete their own footprint.

Why Scope 3 is difficult to calculate

Scopes 1 and 2 are relatively straightforward: you have the energy bills, the data is in your systems. Scope 3 for SME suppliers is more complex, for three reasons.

• It covers activities you don’t control. Your raw material supplier’s emissions, your logistics provider’s practices — you don’t have direct access to them.
• It’s fragmented across multiple sources. Accounting (purchases), expense reports (travel), logistics contracts (transport), or sometimes nowhere at all (tier-2 suppliers).
• The boundaries aren’t always obvious. The standards do answer these questions, but not always in a way that’s intuitive for a non-specialist.

What you actually need to calculate

As an SME supplier answering a client questionnaire, you don’t need to cover the full theoretical scope of Scope 3. Contracting companies generally ask for the most significant items.

1. Purchased goods and services : The most significant item. All your purchasing expenses: raw materials, components, packaging, services. Method: monetary emission factors (kgCO₂e per euro spent) available in the ADEME Base Carbone.
2. Upstream transport and distribution : Emissions linked to the transport of your goods by external service providers. Data needed: tonne-kilometres transported, or failing that, the amount spent on transport.
3. Business travel : Flights, trains, rental cars for business trips. Often low for industrial SMEs, more significant for service companies.
4. Employee commuting : Your employees’ trips between home and work. Data needed: number of employees, average distance, main mode of transport.
5. Production waste : Emissions linked to the treatment of your waste. Depends on the type of waste and the treatment method: landfill, incineration, recycling.

The difference between upstream and downstream Scope 3

Upstream Scope 3 covers everything that happens before your company: your purchases, transport from your suppliers to you, and your employees’ commute to work.

Downstream Scope 3 covers everything that happens afterward: transport to your customers, use of your products, and their end of life.

For a B2B SME supplier, client questionnaires focus mainly on upstream Scope 3: it’s what your contracting company includes in its own “Purchased goods and services” category. Downstream Scope 3 is less often requested at this stage.

The unit of measurement: the tonne of CO₂ equivalent

All emissions are expressed in tonnes of CO₂ equivalent (tCO₂e). This unit unifies gases with different climate effects — CO₂, methane (CH₄), nitrous oxide (N₂O) — according to their global warming potential.

A few reference points to help calibrate your results:

• A round trip Paris–New York: approximately 1.7 tCO₂e per passenger
• One year of driving a petrol/diesel car (15,000 km): approximately 2 tCO₂e
• Annual electricity consumption of a 10-person office in France: approximately 0.5 tCO₂e
• An industrial SME with 50 employees: between 200 and 2,000 tCO₂e depending on the sector

What your client does with your Scope 3 data

Your contracting company adds up the carbon footprints of all its suppliers to calculate its own “Purchased goods and services” category. This is often the heaviest item in its footprint.

When it doesn’t have your data, it uses default sector-wide estimates, often less favourable than your actual footprint, because they don’t account for your specific practices. If you make efforts to reduce your emissions, your actual footprint will be better than the estimate your client would otherwise use in your absence.

The level of precision expected from an SME supplier

The GHG Protocol distinguishes three levels of precision. For a standard supplier questionnaire, level 1 is sufficient.

• Level 1: average sector emission factors applied to monetary spend. Accessible to any SME using its accounting data.
• Level 2: emission factors specific to each type of product or service purchased. Requires more detail in purchasing data.
• Level 3: data collected directly from suppliers. Reserved for large companies with structured supplier programmes.

State your methodology, indicate the confidence level of your data, and your Scope 3 SME supplier report will be considered acceptable.

No specific client request, but you still want to calculate your carbon footprint? Here’s why and how to go about it.

Oakbon calculates your Scope 3
automatically, in 2 hours.

Connect your accounting data, answer 10 questions about your premises and your fleet. Oakbon applies ADEME factors and generates a report ready to send.

From €69/month · No commitment