How to calculate your company’s carbon footprint: a step-by-step guide

The minute

• Start with what has an invoice: fleet fuel, gas and the electricity bill
• Multiply each figure by the official emission factor for your country
• Only then move to scope 3, which is larger and depends on third-party data

Why it matters: The first measurement does not need to be perfect, it needs to be honest and repeatable: the trend is what shows where to cut.

1. Set the boundary

Which sites, which period, what counts. A closed calendar year is the easiest cut to audit later. If your company operates across multiple locations, decide whether you are using operational control or equity share as the consolidation approach. The GHG Protocol Corporate Standard defines both. Operational control means you report emissions from every facility you operate, even if you do not own it entirely. Equity share means you report your ownership percentage of each facility’s emissions. Most companies starting out choose operational control because the data is simpler to collect: if you pay the electricity bill, you report it.

2. Collect what you already invoice

Litres of fuel, cubic metres of gas, kWh of electricity. That is scope 1 and 2, usually an afternoon of work.

Scope 1 covers direct combustion: fuel burned in company vehicles, natural gas in boilers, diesel in generators. Scope 2 covers purchased electricity and, where applicable, purchased steam or cooling. The invoices you already receive from utilities and fuel suppliers contain exactly the activity data you need. Organize them in a single spreadsheet by source, month and unit. Gaps in the invoices (a missing month, an estimate on the bill) should be flagged, not filled with guesses. A note saying “estimated by utility” is more useful than a fabricated number, because it tells the auditor where uncertainty sits.

3. Apply emission factors

Each physical unit becomes CO2e once multiplied by its factor. In Brazil the grid factor published by MCTI is low, because the electricity mix is mostly renewable.

Emission factors translate a physical quantity (one litre of diesel, one kWh of grid electricity) into kilograms of CO2 equivalent. “CO2 equivalent” bundles carbon dioxide, methane and nitrous oxide into a single number using each gas’s global warming potential. For fuels, the factors are relatively stable worldwide because the chemistry of combustion does not change much. For electricity, the factor depends on the generation mix of the grid where you consume power. A grid dominated by hydropower, wind or solar will have a lower factor per kWh than one dominated by coal.

In Brazil, the Ministério da Ciência, Tecnologia e Inovação (MCTI) publishes grid emission factors annually. Because the Brazilian electricity matrix relies heavily on hydroelectric generation, the national grid factor is among the lowest in the world. This means that for many Brazilian companies, scope 2 will be a small share of total emissions, and the real weight falls on scope 1 (fleet fuel, industrial combustion) and scope 3.

The GHG Protocol requires companies to report scope 2 using the location-based method (the average grid factor). Companies with operations in markets that offer contractual instruments, such as Brazil with its renewable energy certificates and free-market contracts, must also report the market-based figure, which uses factors tied to specific energy contracts or certificates. The Scope 2 Guidance calls this dual reporting.

Worked example

Picture a distributor with one warehouse and five trucks. For the calendar year it gathers:

• litres of diesel bought (fuel station invoices or fleet card statements);
• kilograms of refrigerant gas topped up during air-conditioning maintenance (technician work orders);
• kWh from the warehouse’s 12 electricity bills.

Each line gets its factor: diesel and refrigerant from the Brazilian GHG Protocol Programme calculation tool, electricity from the MCTI annual grid factor. The first two add up to Scope 1; the third is Scope 2. The final spreadsheet should show, for every line, the quantity, the unit, the factor, the factor’s source and the result. With that, anyone can redo the calculation next year. Refrigerant leaks are easy to forget, but they are Scope 1 fugitive emissions and can matter in retail and food businesses.

4. Tackle scope 3 by priority

Start with categories that are both large and measurable: freight, travel and purchased goods. State the method instead of faking precision.

The GHG Protocol defines fifteen scope 3 categories. No company needs to quantify all fifteen in the first year. Begin with the categories that are likely to be material: purchased goods and services, upstream transportation and distribution, and business travel are common starting points. For each category, document whether you used a spend-based method (converting currency spent into emissions using economic factors), an activity-based method (using physical quantities like tonne-kilometres), or a supplier-specific method (using data directly from your supplier). Spend-based estimates are the least precise but the easiest to produce. As your measurement matures, the goal is to shift toward activity-based and supplier-specific data, which reduce uncertainty.

5. Document and publish

Record the boundary, the consolidation approach, the factors and their sources, the exclusions and the reason for each. Companies that join the Brazilian GHG Protocol Programme can publish their inventory in the Public Emissions Registry, which awards seals by quality: bronze for a partial inventory, silver for a complete inventory and gold for a complete inventory verified by an independent third party. Purchased carbon credits are reported separately; they do not reduce the gross inventory. For reporting formats by scope, see how to report Scope 1, 2 and 3 in practice.

The most common mistake

The most frequent error is not miscalculating a factor; it is mixing methods between years and then comparing the results as if they were consistent. If you measure freight by spend in year one and by tonne-kilometre in year two, the change in your reported number reflects the change in method, not the change in emissions. This makes the trend meaningless, which defeats the purpose of measuring in the first place. Lock your methodology for at least two consecutive reporting cycles before changing it, and when you do change it, restate the previous year using the new method so the comparison holds.

Brazil: what changes in practice

Brazil’s Programa Brasileiro GHG Protocol, managed by FGVces (the Center for Sustainability Studies at Fundação Getulio Vargas), adapts the global GHG Protocol to the Brazilian context. Companies that join the programme report through the Public Emissions Registry, which publishes inventories openly. Participation has historically been voluntary, but Brazil’s regulated carbon market, established by federal law in late 2024, will require mandatory reporting for emitters above a threshold set by regulation. The implementing rules that define exactly which companies must report, and on what timeline, are still being drafted. Companies that already measure using the GHG Protocol framework will be better positioned when mandatory reporting begins, because the methodology is expected to align closely with what the programme already requires.

What is still unresolved

Two things remain open. First, scope 3 data quality depends on suppliers who may not measure their own emissions. Until reporting cascades through supply chains, scope 3 will rely on estimates and industry averages. Second, the boundary between what counts as a company’s footprint and what belongs to someone else’s is a judgment call in categories like leased assets and investments. Standards provide guidance, but companies still make choices, and those choices affect the number. Disclosing the choices matters as much as disclosing the result.

Frequently asked questions

Do I need a consultancy to start?

Not for the first measurement. Consultants and third-party verification matter when formal assurance is required.

What is the difference between footprint and inventory?

The inventory is the structured measurement process; the footprint is the number it produces.

How often should we measure?

Annually, keeping the same method so year-on-year comparison means something.

Is there a free tool?

Yes. The Brazilian GHG Protocol Programme provides an emissions calculation tool, available after registration on the FGVces website.

Does renewable electricity bring Scope 2 to zero?

Only under the market-based method, and only with a contract or certificate that proves the renewable attribute. Under the location-based method, the average grid factor still applies.

Read next: how to build your first GHG inventory.

Read next: understand scopes 1, 2 and 3.

Read next: what changes with Brazil’s compliance market.

Primary sources: GHG Protocol Corporate Accounting and Reporting Standard, revised edition (WRI/WBCSD, 2004); GHG Protocol Scope 2 Guidance (WRI/WBCSD, 2015); GHG Protocol Corporate Value Chain (Scope 3) Standard (WRI/WBCSD, 2011); Brazilian grid CO2 emission factors for corporate inventories (MCTI, SIRENE); Brazilian GHG Protocol Programme and Public Emissions Registry (FGVces).