GHG Protocol Scope 3 Standard · 6 of 15 categories modelled
Scope 3
Scope 3 is where most carbon software overstates itself. We model six of the fifteen categories. The other nine appear on your board and on your report as stated omissions, so nobody mistakes an incomplete inventory for a finished one.
Last updated 2026-09-05
What is modelled
Six categories, each naming the method used and the data-quality tier it produces. Categories 4 and 9, freight, are calculated by tonne-km against the DESNZ (DEFRA) vehicle averages, or by spend against named USEEIO transport sectors. Category 1 purchased goods and services is spend-based, using the EPA’s USEEIO supply-chain factors, which are denominated per United States dollar. For a non-US organisation that is a United States economic proxy applied to converted spend, and the methodology note on the figure says so rather than leaving it to a footnote.
A spend-based figure is money multiplied by an industry average. It cannot tell a good supplier from a bad one, so it is a starting point rather than a measurement, and it is marked as an estimate everywhere it appears.
What is not, and why that is on the page
Nine categories are not modelled. Hiding them would let a company believe a six-of-fifteen inventory was finished, which is the failure mode that ends a compliance vendor. The completeness register lists all fifteen, marks the nine, and the filed report prints them as stated omissions.
We will not claim "full Scope 3" or "all 15 categories". If a competitor’s feature grid says otherwise, ask them which method each category uses and what data-quality tier it produces.