Calculate your company's carbon footprint: from invoices to a first inventory with the GHG Protocol

A large customer sends a supplier questionnaire asking for your greenhouse gas emissions, and your bank asks the same at the annual review. To calculate your company's carbon footprint the first time you need a year of invoices, the right emission factors and a clear rule on what counts. Often two or three sources make up the bulk of the total, and within your own operations they are usually energy and fuel, the same lines that drive your costs.

The rules on what counts come from the GHG Protocol Corporate Standard of the World Resources Institute (WRI) and the World Business Council for Sustainable Development (WBCSD). This page covers its three scopes, official factors per country, how to count electricity and a fictitious first inventory.

Why calculate your company's carbon footprint?

• Savings: fuel, gas and electricity are usually the largest direct sources, so each tonne avoided there saves money.
• Customer questions: your emissions are part of your customers' value chain, so larger customers ask their suppliers for data.
• Tenders and finance: some public buyers and lenders ask for one; see sustainable procurement.
• Honest claims: a measured footprint is the only safe basis for any climate statement; see green claims.

Scope 1, 2 and 3: what counts?

Scope 1: direct emissions

Emissions from sources owned or controlled by the company (source: GHG Protocol, March 2004). Think of gas boilers, company vehicles, process emissions and refrigerant leaking from cooling equipment.

Scope 2: purchased energy

Indirect emissions from the electricity, steam, heat or cooling you buy (source: US EPA, April 2026).

Scope 3: the value chain

All other indirect emissions, upstream at your suppliers and downstream at your customers, grouped into 15 categories (source: GHG Protocol, October 2026). The Corporate Standard requires scope 1 and 2 at a minimum and treats scope 3 as optional (source: GHG Protocol, March 2004), yet scope 3 often represents the majority of an organisation's emissions (source: US EPA, May 2022).

You do not need all of them at once. An office firm starts with travel, commuting and purchased services; a shop with purchased goods and transport; a manufacturer with materials and transport; a restaurant with food purchases and waste.

How to calculate emissions: activity data times emission factor

Carbon dioxide equivalent (CO₂e) expresses other greenhouse gases, such as methane or refrigerant gases, as the amount of carbon dioxide with the same warming effect. Physical units give the most reliable result. For purchases you often have only the amount spent, and a spend-based factor gives a rough first estimate. The UK government notes that spend-based multipliers differ from its conversion factors and asks users to report the methods they used (source: GOV.UK, July 2026).

Where to find official emission factors

• Same year: use the factor set for the year your data covers.
• One set, one method: some sets include the upstream emissions of producing and transporting fuel, others do not. Choose and stay consistent.
• Check your country: sets are revised every year, so record which set and version you used, and use the grid factor for where you consume.

How to count electricity: location-based or market-based

The location-based method uses the average emissions of the grid where you consume. The market-based method reflects the contracts you choose, such as a renewable tariff backed by certificates. Under the GHG Protocol Scope 2 Guidance, companies report scope 2 under both methods (source: Deloitte, October 2026), and contractual instruments must meet quality criteria before they count in the market-based figure (source: GHG Protocol, October 2026). The guidance is being revised after a public consultation that ran from October 2025 to January 2026 (source: GHG Protocol, October 2026). Ask your supplier for proof that certificates were cancelled in your name before you report a lower figure.

Worked example: an office fit-out firm's first footprint

Redfern Office Interiors has 28 staff and €3.2 million revenue. It designs and builds office interiors, heats its workshop with gas, runs four diesel vans and buys board, steel and fabrics. Commuting comes from a short staff survey, the rest from invoices and the fuel card.

Fictitious Firmfocus example. The factors are round illustrative numbers, not official values: use the current set from your country's official source. 9,000 x 2.0 = 18,000 kg; 10,000 x 2.7 = 27,000 kg; 60,000 x 0.30 = 18,000 kg; 400,000 x 0.40 = 160,000 kg; commuting 28 staff x 220 days x 20 km = 123,200 km x 0.17 = 20,944 kg. Total 18.0 + 27.0 + 18.0 + 160.0 + 20.9 = 243.9 tonnes. The logic works in any currency.

Purchased materials make up about two-thirds of the total (160.0 / 243.9 = 66%), but that line is a spend-based estimate and the least precise. Scope 1, at 45 tonnes, is where Redfern acts directly: route planning and electric vans when the leases end, and better insulation and controls in the workshop. Its renewable contract, backed by certificates, gives a market-based electricity figure of 3.0 tonnes, so Redfern reports 243.9 tonnes location-based and 228.9 tonnes market-based. Per employee that is 8.7 tonnes (243.9 / 28), and per million euros of revenue 76.2 tonnes (243.9 / 3.2). Next year it will ask its main board suppliers for product data to replace the spend estimate.

Your first footprint in six steps

1. 01

   Set the boundary

   Choose the equity share or the control approach, financial or operational, and list the sites and vehicles that fall inside it.

2. 02

   Collect a full year of data

   Energy invoices, fuel cards, refrigerant records, travel bookings and purchases.

3. 03

   Apply one official factor set

   Use factors for the same year from a single source and note the version.

4. 04

   Fix a base year

   Document any later change in data, boundary or method so years stay comparable.

5. 05

   Set targets

   Add an intensity measure, per employee or per unit of revenue, so growth is not mistaken for failure.

6. 06

   Use it more than once

   Answer customer questionnaires, feed your sustainability report and keep claims within what you measured.

If a customer or lender wants assurance, ISO 14064-1 specifies principles and requirements at organisation level for quantifying and reporting greenhouse gas emissions and removals (source: ISO, October 2026), and a verifier can check your inventory against it.

Small business or larger company

Pitfalls

• Mixing factor sets or years: the change in your total then says more about the factors than about you.
• A green contract without proof: no certificates, no lower market-based figure.
• Trusting spend-based numbers too much: a price rise then looks like an emissions rise.
• Double counting: electricity for charging electric vans counts once, as purchased electricity, not again as vehicle fuel.
• Claims beyond the data: a partial footprint does not support a "climate neutral" message.

Own generation and smarter use cut purchased-energy emissions, as shown on solar, batteries and grid congestion, and fleet and commuting choices under sustainable mobility. For the full set of topics, start at Sustainable business.