How Calyx Ratings Work

Calyx GHG Risk Ratings and SDG Impact Ratings comprise decades of experience with carbon crediting standards and SDG certifications. We have developed ratings frameworks that allow us to assess GHG risk and SDG impact. Our frameworks account for differences among project types, standards and impact claims, yet always allow users to compare resulting ratings.

Greenhouse Gas Integrity Risk Ratings

Our GHG Integrity Framework lays out Calyx Global’s approach to assessing risks that carbon credits do not meet their claims of reducing or removing the equivalent of one metric ton of CO2.

1 – Screening of Crediting Standards

Calyx Global only rates credits issued by standards that meet our minimum criteria

This includes criteria based on:

  • governance
  • rules and procedures
  • stakeholder consultations
  • ensuring transparency
  • validation and verification
  • registry operations
Carbon Standards eligible for Calyx Ratings

We recommend buyers focus on purchasing credits from standards that meet our minimum criteria.

2 – Calyx Methodology Assessments & Ratings

Calyx methodology assessments combine a review of the inherent risks of the activity type with how methodologies / protocols used for crediting can mitigate those risks.

Mesh (mobile)
Methodology-level ratings

Calyx Methodology Ratings provide information on the strength of the rules used by projects to claim emission reductions (or removals) and to focus our project-level ratings on the key issues that cause variability in credit quality project-to-project.

3 – Project Assessments & Ratings

Calyx Global rates individual projects. To do so, we build project-level assessment approaches based on the same framework we use to rate methodologies and the same GHG risk criteria to promote comparability, but with more granular guidance for specific project-level activity.

Project-level ratings

Our project-level ratings provide buyers with in depth assessments and comparable ratings of the GHG integrity risks of specific credits.

GHG Risk Assessment Criteria

Calyx Global’s GHG Integrity Framework uses a risk-based approach. The following criteria are used to assess the claims of emission reductions or carbon removals.


Risk that the project generating credits would have been implemented without carbon revenue.


Risk that the credited mitigation will be reversed and, if so, not fully compensated.


Risk that the project baseline overestimates emissions or underestimates removals that would have occurred in the absence of revenues from carbon credits.

Project Emissions

Risk that the project emissions are underestimated or removals overestimated, leading to overestimating emission reductions.


Risk that the project does not account for emissions (or reduced removals) induced by the project activity, but fall outside the project boundary.

Overlapping claims

Risk that the carbon credit does not represent an exclusive claim to an emission reduction or removal.

SDG Impact Ratings

Calyx Global rates claimed project contributions to UN Sustainable Development Goals (SDGs). We only rate claims of contribution if these are part of a recognized SDG certification. Our approach to assessing claimed project contributions to the SDGs takes into account:

SDG Mesh
SDG Mesh Mobile

1 – Level of Change Achieved

For each SDG contribution identified, we evaluate whether there is evidence of a clear link between project activities and resulting outputs, outcomes or impacts. This assessment is done at the level of SDG targets for individual SDGs.

E.g. SDG Target 2.1 – Increase Access to Food (“By 2030, end hunger and ensure access by all people, in particular the poor and people in vulnerable situations, including infants, to safe, nutritious and sufficient food all year round”), which is part of SDG 2 – Zero Hunger (“End Hunger, Achieve Food Security and Improved Nutrition and Promote Sustainable Agriculture”)


Specific actions the project is implementing

E.g. Planting of fruit and nut trees.



Immediate and tangible deliverable by project activities.

E.g. number of fruits or nut trees planted.



Change that an output may start to bring about. Change at the level of Outcome is given the heaviest weighting because recently started projects may not have reached significant impacts yet and/or because it is difficult to attribute impacts exclusively to project activities.

E.g. volume of food produced (and consumed).



Real world changes effected by the project. Impact may only be partially attributable to project.

E.g. number of people experiencing increased food security.

2 – Attributability of Change Achieved

We assess the degree to which SDG Contributions are attributable to the project. This assessment is done at the level of SDG targets for individual SDGs.

Weak to Strong Attribution

Predicted (plan)

The contribution has not been verified or documented.


Narrated (actual)

The contribution is described in qualitative terms.


Estimated (actual)

The reporting provides an estimation of the contribution.


Quantified (actual)

Actual and quantifiable contribution data on the contribution is provided.


Clear Methodology (actual)

Clear methods and units to measure change are provided.

3 – Scoring and Rating

Individual claims of contribution to SDG Targets are assessed on Level of Change and Attributability. The combined assessments result in a score that corresponds to a Calyx Rating for the contributions. SDG Target ratings are aggregated in overall SDG ratings, which are, in turn, aggregated in an overall SDG Impact Rating for the project.

SDG Impact ratings

Project-level rating of each SDG contribution that is claimed