GHG Inventory & Corporate Carbon Accounting Calculators

What a corporate GHG inventory covers

A complete inventory is not a pile of source numbers — it is those numbers assembled on one boundary and one consolidation approach, so the total means something. The work splits into three questions: which entities and sources are in scope, how you calculate each source, and how you roll them into a single figure. Where you are in that sequence decides which calculator you need.

Going deeper on the value chain? The Scope 3 value-chain emissions sub-topic hub collects the upstream and downstream categories — Categories 1-2 and 8-14 — in one place.

Pick your inventory calculator

Know what you’re building? Go straight to the calculator.

Which calculator do I need?

Two of these tools assemble a whole inventory; the other five each close one value-chain Scope 3 category. This table maps what each measures, the scope it sits in, and when to reach for it.

What each calculator covers

The decision table tells you which tool to open; this section tells you what each one actually estimates and where the accounting traps sit. The two roll-up tools assemble; the five category tools each resolve one value-chain question that a boundary decision leaves open.

The roll-up — full inventory and ISO 14064-1

The Scope 1, 2 & 3 aggregator is the hub node of this cluster: it takes the totals from every source calculator and combines them into one Scope 1+2+3 figure on a single boundary, which is the number disclosure and target-setting actually consume (methodology). The ISO 14064-1 inventory calculator does the same assembly but organises the result to the ISO standard’s structure, which matters when the inventory is headed for third-party verification rather than a voluntary disclosure (methodology). Use the aggregator when you want the fastest defensible total; use the ISO tool when the framework of the report is itself a requirement.

Leased assets — Cat 8 upstream and Cat 13 downstream

Leased assets are the most double-counted line in a Scope 3 inventory, because the direction of the lease decides the category and the two are easy to confuse. The Category 8 calculator covers assets you lease in and operate that are not already captured in your Scope 1 and 2 (methodology). The Category 13 calculator covers the reverse — assets you own and lease out to others (methodology). Which one applies follows from your consolidation approach, so settle the boundary first.

Sold products — Cat 10 processing and Cat 11 use

Two categories cover what happens to your product after it leaves you. The Category 10 calculator covers intermediate products that a downstream customer processes further before final sale, estimated from the processing emissions your output triggers (methodology). The Category 11 calculator covers the use phase — the fuel or electricity a product consumes over its lifetime in the customer’s hands, which for energy-using products often dominates the whole footprint (methodology). Both depend on a use or processing assumption the methodology sets out.

Franchises — Cat 14

The Category 14 calculator covers franchise operations that fall outside your consolidation boundary — the emissions of franchisees you don’t operationally or financially control (methodology). If a franchise is inside your control boundary its emissions belong in Scope 1 and 2 instead, which is exactly why the consolidation choice below has to come before this calculation, not after.

GHG Protocol, ISO 14064-1 and consolidation

Two questions cause more inventory rework than any factor choice: whether the GHG Protocol and ISO 14064-1 are interchangeable, and which entities’ emissions are yours to report. Both are boundary questions, and both are worth settling before you calculate a single source.

On the standards: the GHG Protocol Corporate Standard and ISO 14064-1 are broadly aligned and often used together — ISO 14064-1 is designed to be compatible with the GHG Protocol’s scopes and principles — but they are not identical in structure or terminology, and a verifier working to ISO expects the inventory organised to that standard’s categories. The practical rule is to pick the framework your disclosure or verification requires and build to it, rather than assuming a GHG Protocol inventory drops cleanly into an ISO report.

The 2018 edition of ISO 14064-1 replaced the three-scope model with six categories. Every source still maps to exactly one category and the totals match, so a GHG Protocol inventory re-aggregates into ISO form with no recalculation:

On consolidation: before any source is counted, you choose how to draw the organizational boundary — the operational-control, financial-control or equity-share approach. That choice determines which entities’ emissions are Scope 1 and 2 versus which fall to Scope 3, and it is the hinge for the leased-asset and franchise categories above. A franchise or leased asset inside your control boundary is direct emissions; the same asset outside it is a value-chain category. The operational control approach is the most common, but the honest answer is that the right one depends on how your group is structured and what your disclosure regime expects — so decide it explicitly and apply it consistently across every source.

The three approaches differ in which entities’ emissions you claim — and it is the same choice that fixes where each leased asset and franchise belongs:

How the numbers are built

Every calculator here draws on the same versioned factor set as our source-level Scope 1, 2 and 3 tools — the aggregator does not re-estimate anything, it combines totals that were each built on a named standard. The inventory sits under the GHG Protocol Corporate Standard and ISO 14064-1; value-chain sources follow the GHG Protocol Scope 3 Standard; Scope 2 lines follow the GHG Protocol Scope 2 Guidance and its dual location- and market-based method. Every emission factor and global warming potential is versioned in the MasterBrain data layer, so an inventory records which vintage produced each number, and each source has a matching methodology page setting out its assumptions. Where a national dataset applies, disclosure aligned to a scheme such as GRI 305 emissions reporting can be structured from the same totals.

One provenance point matters for a roll-up specifically: a total is only consistent if its parts share a basis. Corporate GHG reporting defaults to AR6 GWP-100 values, and that is the basis these calculators apply; where a factor is DEFRA-sourced it may carry an AR5 basis by design, and the two should never be mixed inside a single total. Because the aggregator sums sources that were each estimated independently, it inherits whatever basis those sources used — so the discipline is to keep one GWP basis across the whole inventory, which each source calculator states so the totals combine on a consistent footing.

After your first number

A corporate inventory is rarely the first thing you calculate — it is what the source-level numbers assemble into. Most footprints start at the source: the fuel burned on-site, the electricity purchased, the business travel and freight, then the value-chain categories here. The aggregator is the point where those separate totals become one auditable figure on a single boundary.

Once the inventory is complete it feeds the work downstream of it. A baseline inventory is what a reduction target is set against, and what most disclosure regimes require you to report — the target-setting cluster and the disclosure calculators both start from the number this hub produces. A financial institution’s inventory has its own value-chain problem in its lending and investment book, covered by the financed emissions calculators. Target-setting and net-zero pathway tools are a separate cluster referenced in the related tools below. The full carbon calculator directory covers every source-level tool the inventory draws on.