Measuring Your Carbon Footprint: ISO 14064 in Practice

13 Οκτ 2026 · @Nikos Stavropoulos

Introduction

A carbon footprint is only useful if it is complete, consistent and credible enough to guide decisions, and ISO 14064 is the international standard family that sets the rules for that. Part 1 covers the organisation, Part 2 covers individual reduction projects and Part 3 covers verification [1][2][3]. This article explains what to measure, how to set boundaries and how to turn the results into reduction targets. The field is changing. ISO and the GHG Protocol agreed in September 2025 to merge their corporate accounting standards, and the SBTi published a new Net-Zero Standard in June 2026 [4][5][12]. I therefore separate what is settled from what is still moving. Statements that are my inference rather than a cited finding are labelled as such.

What ISO 14064 covers?

The current editions of all three parts remain valid, but ISO has started revising Parts 1 and 2. ISO's catalogue pages show each part as reviewed and confirmed in 2024 [1][2][3].

The standard is neutral between GHG programmes, so a programme's own requirements apply in addition [1].

On 9 September 2025, ISO and the GHG Protocol announced a partnership to harmonise their standards and develop co-branded ones [5]. According to the GHG Protocol's development plan of 29 July 2026, a consolidated Corporate Standard (version 3.0) will integrate the Corporate Standard, Scope 2 Guidance, Scope 3 Standard and a new Actions and Market Instruments framework with ISO 14064-1. The plan estimates a public consultation in Q2 2027 and publication in Q4 2028, and calls these estimates [4]. A trade-press report adds that the Scope 3 consultation draft, due in the second half of 2026, may be adjusted to fit the integration work [6]. In practice, my inference is that a company starting today should build its inventory on the current ISO 14064-1 and GHG Protocol rules, document its choices well, and expect to recalculate when the merged standard appears.

What to measure?

Measure direct emissions, emissions from purchased energy and, where they matter, the indirect emissions in your value chain. The GHG Protocol groups these as three scopes and ISO 14064-1:2018 as six categories [7][9].

The GHG Protocol treats Scope 3 as an optional reporting category for "all other indirect emissions" [7]. ISO 14064-1:2018 is stricter on one point: the organisation must assess the significance of every indirect category and justify any it leaves out in its documentation [9].

The size of the indirect share is a reason to take Scope 3 seriously. A global input-output study found that between 1995 and 2015 Scope 1 emissions rose 47%, Scope 2 rose 78% and Scope 3 rose 84%. In 2015 the three totalled 32, 10 and 45 Pg CO2, and for industry alone Scope 3 was 32 Pg against 5 Pg for Scope 2 [11]. That result is about the whole economy, not any one company, so the split for your company has to be measured.

How to set boundaries?

Choose the organisational boundary first, then the sources inside it, and fix a base year you can defend. The GHG Protocol offers three approaches to the organisational boundary [7]:

• Equity share: emissions are counted according to the company's share of equity in each operation.
• Financial control: the company has the ability to direct the financial and operating policies of the operation.
• Operational control: the company has the full authority to introduce and implement its operating policies at the operation.

The standard rests on five principles: relevance, completeness, consistency, transparency and accuracy [7]. For a service company, my suggestion is operational control, because it usually matches who can actually change the emissions, but the choice must be documented and applied consistently. The base year is the fixed reference against which later emissions are compared. The GHG Protocol requires recalculation when structural changes (mergers, acquisitions, divestments, outsourcing), changes in methodology or data accuracy, or significant errors affect it. It does not require recalculation for organic growth or for real changes such as a switch of fuel or technology. The standard sets no numeric threshold for "significant": each company defines and discloses its own, and it gives a 10% cumulative threshold used by one registry only as an example [7]. ISO 14064-1:2018 added more explicit requirements for when and how to recalculate the base year [9].

Data quality, uncertainty and verification

The most common weakness in corporate footprints is incompleteness, not arithmetic. A study of 56 technology companies compared their self-reported 2019 Scope 3 emissions with a harmonised estimate. The reports totalled 360 MtCO2e against 751 MtCO2e harmonised, so the paper states that corporate reports omit half of the total emissions. About 30% of companies left out purchased goods and services and 43% left out use of sold products. Companies with progressive reduction pledges, such as Microsoft, Google and Apple, showed gaps below 20% [10]. This is one sector and one year, so it shows what can go wrong, not how all companies perform.

ISO 14064-1:2018 strengthened its requirements for assessing and reporting uncertainty [9]. Verification under Part 3 is done by an independent third party and gives one of two levels of assurance [9][3]:

• Reasonable assurance: the verifier concludes that the GHG statement is fairly stated, after more extensive testing.
• Limited assurance: the verifier reports that nothing suggests the statement is wrong, based mainly on inquiry and analytical procedures.

My suggestion is to build the audit trail from the start: record each activity datum, its source, the emission factor and its version, and every exclusion with its reason. That is what makes verification possible later and satisfies the transparency principle [7].

From emissions data to reduction targets

The inventory shows where emissions are largest, and the targets should start there. The SBTi Corporate Net-Zero Standard Version 2.0, announced around 11 June 2026, is the main external framework for this. According to a press summary of it [12]:

• All companies must set near-term (five-year) Scope 1 and 2 targets.
• Only Category A companies, meaning large companies everywhere and medium-sized companies in high-income countries, must set near-term Scope 3 targets and obtain limited assurance on base-year data.
• Scope 1 targets may be absolute, intensity-based or asset-transition. Scope 2 targets may cut emissions or raise the share of low-carbon electricity.
• Scope 3 options include an overall absolute target, a supplier and customer alignment approach, or a category-specific approach. Limited exclusions are allowed, such as categories below 5% of Scope 3.

The summary does not state when the new standard takes effect, so check the SBTi document itself [12]. Small companies fall in Category B, which has lighter obligations.

My suggested sequence is to rank emission sources by size, pick the few that make up most of the total, assign an owner and an action to each, and set a target that you can track against the base year. A reduction target is only as reliable as the inventory behind it, so complete the inventory first [10].

Limits of the evidence

There is little research on ISO 14064 itself, so most support here comes from the standards' own texts and a small number of studies. The underreporting study covers 56 technology companies in 2019 [10], and the input-output study describes the global economy, not companies [11]. Several sources on the GHG Protocol timeline and the SBTi standard are secondary summaries from trade media and law firms, and the plans are estimates that may move [4][6][12]. I could not read ISO 14064-1 in full, so I rely on ISO's catalogue page and on a certification body's guide for the six categories and assurance levels [1][9]. Check the standards themselves before advising a client.

References

1. ISO (2018). ISO 14064-1:2018 Greenhouse gases — Part 1. ISO catalogue page.
2. ISO (2019). ISO 14064-2:2019 Greenhouse gases — Part 2. ISO catalogue page.
3. ISO (2019). ISO 14064-3:2019 Greenhouse gases — Part 3. ISO catalogue page.
4. GHG Protocol (2026). Consolidated Standard Development Plan, version 2.0, 29 July 2026.
5. Beveridge & Diamond (2025, updated 2026). GHG Protocol Announces ISO Partnership to Develop Unified Carbon Accounting Standards.
6. Trellis (2026). GHG Protocol adjusts standards update timelines.
7. WRI & WBCSD. The Greenhouse Gas Protocol: A Corporate Accounting and Reporting Standard, revised edition.
8. GHG Protocol. Corporate Standard. Web page.
9. GlobalCert (n.d.). What is ISO 14064-1 verification?
10. Klaaßen, L., & Stoll, C. (2021). Harmonizing corporate carbon footprints. Nature Communications, 12, 6149. Article
11. Hertwich, E. G., & Wood, R. (2018). The growing importance of scope 3 greenhouse gas emissions from industry. Environmental Research Letters, 13(10), 104013. DOI: 10.1088/1748-9326/aae19a
12. ESG Today (2026). SBTi Releases Finalized New Corporate Net Zero Standard.