This document explains the data sources, emissions factors, scoring logic, and known limitations behind the Carbon3 Scope 3 Exposure Calculator. Transparency in methodology is a prerequisite for defensible compliance — and we hold ourselves to the same standard.
The Carbon3 Scope 3 Exposure Calculator is a rapid-assessment tool designed to give enterprise decision-makers an evidence-based starting point for understanding their regulatory exposure under SB-253 (California Climate Corporate Data Accountability Act) and related Scope 3 frameworks. It is not a substitute for a full GHG inventory, but it is built on the same data standards that inform one.
The calculator takes five structured inputs — industry sector, annual revenue, supplier count, supply geographies, and current tracking maturity — and returns three outputs: a Compliance Readiness Score (0–100), an estimated tCO₂e emissions exposure range, and a prioritised gap analysis. Each output is grounded in published emissions factors and sector benchmarks from the sources listed in Section 7.
"Scope 3 emissions — those occurring in a company's value chain — typically represent 70% or more of an organisation's total carbon footprint and are the primary target of emerging mandatory disclosure regulation."
The calculator is calibrated against the following active regulatory and voluntary disclosure frameworks. Each has distinct scope and threshold requirements; the model uses the most demanding applicable threshold as the baseline for scoring.
| Framework | Jurisdiction | Scope 3 Requirement | Status |
|---|---|---|---|
| SB-253 (CCDAA) | California, USA | Mandatory for companies >$1B revenue operating in CA. Full Scope 1, 2, 3 disclosure. Good-faith window closes August 10, 2026. | Active — enforcement 2027 |
| SB-261 | California, USA | Climate-related financial risk disclosure for companies >$500M revenue. Includes value chain exposure. | Active — biennial reports |
| CSRD / ESRS E1 | European Union | Mandatory Scope 3 disclosure for EU-listed companies and large subsidiaries. Category-level granularity required. | Phased — 2024 to 2028 |
| EU CSDDD | European Union | Due diligence on value chain human rights and environmental impacts. Scope 3 mapping is a prerequisite. | Transposition by 2026 |
| GHG Protocol Corporate Standard | Global | Primary methodology standard. Defines the 15 Scope 3 categories used as the structural basis for this calculator. | Industry standard |
| CDP Climate Questionnaire | Global | Voluntary but investor-facing. Scope 3 completeness is a scored metric. Increasingly required by institutional procurement. | Annual — voluntary |
The calculator uses a spend-based estimation approach — the method recommended by the GHG Protocol for Scope 3 Category 1 (Purchased Goods and Services) when primary supplier data is unavailable. This is the most widely applicable method for an initial exposure assessment and is explicitly accepted under SB-253 good-faith reporting guidance.
The core formula is:
Estimated tCO₂e = Revenue Proxy × Sector Emissions Intensity Multiplier
Revenue proxy is the midpoint of the revenue band selected, treated as a gross spending proxy for upstream supply chain activity. This is a standard approximation in the absence of primary procurement data, consistent with EPA's EEIO methodology.
Sector emissions intensity multipliers are derived from the EPA's Environmentally Extended Input-Output (EEIO) model v1.1 and cross-referenced against IPCC AR6 Working Group III sector benchmarks. The multipliers below represent kg CO₂e per dollar of economic output for each sector:
| Sector | Intensity Multiplier | Primary Scope 3 Categories | Source Basis |
|---|---|---|---|
| Manufacturing | 2.1× | Cat. 1 (Purchased Goods), Cat. 4 (Upstream Transport), Cat. 11 (Use of Sold Products) | EPA EEIO v1.1 / IPCC AR6 WGIII Ch. 11 |
| Logistics | 1.8× | Cat. 4 (Upstream Transport), Cat. 9 (Downstream Transport), Cat. 1 (Purchased Fuel) | EPA EEIO v1.1 / IPCC AR6 WGIII Ch. 10 |
| Construction | 1.6× | Cat. 1 (Purchased Materials), Cat. 4 (Transport), Cat. 11 (Built Asset Use) | EPA EEIO v1.1 / IEA Buildings 2023 |
| Food & Beverage | 1.4× | Cat. 1 (Agricultural Inputs), Cat. 2 (Processing), Cat. 11 (Consumer Use) | EPA EEIO v1.1 / FAO FAOSTAT 2023 |
| Apparel | 1.3× | Cat. 1 (Raw Materials), Cat. 4 (Logistics), Cat. 11 (Consumer Washing) | EPA EEIO v1.1 / Higg Index MSI 2023 |
| Technology | 0.9× | Cat. 1 (Hardware/Components), Cat. 11 (Device Energy Use), Cat. 15 (Investments) | EPA EEIO v1.1 / GeSI SMARTer 2030 |
| Financial Services | 0.5× | Cat. 15 (Financed Emissions), Cat. 6 (Business Travel), Cat. 7 (Employee Commute) | EPA EEIO v1.1 / PCAF Standard 2022 |
| Other | 1.0× | General value chain — Cat. 1, Cat. 4, Cat. 11 | EPA EEIO v1.1 cross-sector average |
The resulting estimate is presented as a ±40% confidence range (lower bound at 70%, upper bound at 140% of the point estimate), consistent with the uncertainty range documented in the GHG Protocol's Scope 3 Calculation Guidance for spend-based methods at this level of input resolution.
The Compliance Readiness Score (0–100) is an inverse-risk index: a higher score indicates greater current readiness; a lower score indicates greater compliance gap. The score begins at 100 and is reduced by weighted penalty factors derived from the five assessment inputs.
The weighting structure reflects the relative contribution of each factor to Scope 3 audit risk, based on SB-253 enforcement guidance and GHG Protocol assurance requirements:
The single largest determinant of compliance readiness. No systematic tracking (−45) reflects the absence of any auditable data trail. Manual/spreadsheet tracking (−30) is insufficient for SB-253 third-party assurance. Basic software (−15) meets minimum thresholds but lacks the category-level granularity required for full disclosure. Advanced integrated systems (−5) represent near-ready posture.
Supplier visibility degrades non-linearly with count. Research from CDP and the Science Based Targets initiative (SBTi) consistently shows that Tier 1 visibility drops below 30% at 50+ suppliers without systematic data collection infrastructure. Penalty reflects the statistical probability of material undisclosed emissions.
High-scrutiny geographies (China, Southeast Asia, India, Latin America) carry elevated audit risk for two compounding reasons: emissions factor uncertainty is highest in regions with weaker national inventory reporting, and cross-border data collection is operationally harder to enforce. Each high-scrutiny geography deducts 5 points.
Sector does not directly adjust the score but drives the emissions intensity multiplier used in exposure estimation. High-intensity sectors (Manufacturing, Logistics) face greater scrutiny under SB-253 because their Scope 3 categories are both larger and more auditor-visible. This contextual risk is surfaced in the gap analysis.
Score interpretation bands, calibrated against SB-253 enforcement risk tiers:
The gap report surfaces the four highest-priority risk factors from a library of condition-triggered findings. Each finding is generated deterministically from the assessment inputs — not probabilistically or through machine learning. This means the output is fully reproducible and auditable: the same inputs always produce the same findings.
Risk conditions and their basis:
| Condition | Finding Triggered | Regulatory Basis |
|---|---|---|
| Tracking: None or Manual | No auditable emissions data trail — fails SB-253 third-party assurance requirement | SB-253 §3.2 — Third-Party Assurance; GHG Protocol Assurance Standard 2023 |
| Geographies: China or SEA | Elevated emissions factor uncertainty and regulatory scrutiny in high-scrutiny corridors | IPCC AR6 WGIII — Regional Uncertainty Ranges; SEC Climate Rule comment record |
| Suppliers: 50+ (any tier) | Tier 1 visibility below 30% — statistically significant undisclosed emissions risk | CDP Supply Chain Report 2023; SBTi Supplier Engagement Guidance 2022 |
| Industry: Manufacturing, Logistics, Construction, Apparel | Above-average Scope 3 intensity — Category 1 and 4 likely represent majority of footprint | EPA EEIO v1.1; IPCC AR6 sector benchmarks |
| Geography: Mexico | Tariff volatility creates dual exposure: cost disruption and emissions reporting discontinuity | USTR Section 232/301 tariff schedules 2025; GHG Protocol — boundary-setting under supply disruption |
| All assessments | SB-253 good-faith window closes August 10, 2026 — infrastructure built now is defensible in 2027 | California Air Resources Board — SB-253 Implementation Guidance, January 2025 |
This calculator is designed for rapid directional assessment. It produces defensible estimates, not audited figures. The following limitations are inherent to the methodology and should be understood before acting on the results:
The outputs of this calculator are estimates based on publicly available sector data and declared inputs. They do not constitute a GHG inventory, a third-party verified emissions disclosure, or legal compliance advice. Carbon3 and Informd are not responsible for regulatory determinations made on the basis of this assessment alone. For purposes of SB-253 filing, a verified GHG inventory prepared by a qualified third-party assurance provider is required.
All quantitative inputs are drawn from publicly available, peer-reviewed, or regulatory sources. No proprietary or unverifiable data is used in the scoring or estimation models.