ESG ratings can shape how investors, lenders and other stakeholders view a company. But the score alone can be misleading.
Different providers use different data, methodologies and definitions of what matters, so the same company can receive very different ratings without either assessment necessarily being wrong.
In this blog, we explore what ESG ratings actually measure, how they are calculated, why they can disagree and what companies can do to build stronger ESG data and performance behind the score.
What does an ESG rating actually tell you?
An ESG rating is an assessment of how a company performs against a defined set of environmental, social and governance criteria.
These assessments are usually produced by specialist providers such as MSCI, Sustainalytics and S&P Global, and the result might appear as a:
- Numerical score
- Letter grade
- Risk category
- Ranking relative to industry peers
The terminology is not always consistent. One provider may call its output a score, another a rating, and another a risk assessment. The more important question is what sits behind that result.
Different methodologies may assess areas such as:
- Exposure to environmental, social and governance risks
- How effectively those risks are managed
- Sustainability policies and governance structures
- Quantitative performance, including emissions or workforce data
- Controversies and other external events
- Performance relative to companies in the same sector
This is why an ESG rating can’t be treated as a universal grade for how sustainable a company is.
A high rating may indicate that a company manages financially material ESG risks well under one provider’s methodology. It doesn’t necessarily mean the company has the lowest environmental impact, the strongest social performance or the best governance practices across every measure.
Before interpreting the result, it is important to understand what the provider measures, which data it uses and how the different factors contribute to the final rating.
How are ESG ratings calculated?
There is no single formula for an ESG rating. Each provider applies its own methodology, but the process usually follows a similar pattern.
1. ESG data is collected
Rating providers build their assessment using information such as:
- Sustainability and annual reports
- Regulatory disclosures
- Carbon and environmental data
- Workforce and governance metrics
- Company policies and targets
- Public databases and external research
- News and controversy monitoring
The mix of company-reported and external data can vary considerably between providers.
2. Material ESG issues are identified
Not every ESG issue is equally relevant to every business.
A manufacturing company, for example, may face greater exposure around emissions, energy use and supply chains, while a software company may be assessed more heavily on areas such as data privacy, workforce practices or governance.
Providers determine which ESG issues are most material to the company or sector being assessed.
3. Performance is assessed and weighted
Individual indicators are then evaluated and combined according to the provider’s methodology.
Different providers may place greater weight on factors such as:
- Climate risk and emissions
- Human capital
- Supply-chain practices
- Corporate governance
- Business ethics
- Controversies
This weighting helps explain why two agencies can look at similar company information and still arrive at different conclusions.
In action: For example, MSCI ESG Ratings assess companies against the ESG risks and opportunities considered most relevant to their industry. A manufacturer may face greater scrutiny around carbon emissions, water use or worker safety, while a software company may have a different set of material issues. MSCI then considers both the company’s exposure to those issues and how effectively they are managed, before applying issue-specific weightings and comparing performance with industry peers. The result is expressed on a scale from AAA to CCC.
Why can the same company receive different ESG ratings?
Research from MIT Sloan found that ESG ratings from major providers showed relatively low correlation, with most of the disagreement coming from differences in measurement and scope, rather than weighting alone. Measurement differences accounted for 56% of rating divergence, scope for 38% and weighting for 6%.
The main reasons include:
- Scope: One provider may assess issues that another excludes
- Measurement: Providers may use different indicators to assess the same ESG topic
- Materiality: Different methodologies may disagree on which risks or opportunities matter most
- Weighting: The same issue can contribute more heavily to one rating than another
- Data sources: Providers may rely on different disclosures, estimates, external datasets or reporting periods
- Benchmarking: Some ratings assess companies relative to industry peers, while others use different comparison methods
- Controversies: External events may be incorporated differently or reflected at different speeds
For anyone using ESG ratings, this means the headline result only becomes useful once the methodology behind it is understood.
How should you interpret an ESG rating?
The most useful way to read an ESG rating is to look beyond the score itself and ask how it was produced.
| Questions to ask | Why it matters |
| Who produced the rating? | Providers use different methodologies, datasets and scoring systems |
| What does it measure? | Some ratings focus on ESG risk, while others place more emphasis on policies, performance or peer comparison |
| What data was used? | Missing, estimated or outdated information can affect the result |
| Which issues carry the most weight? | Climate, workforce, governance or other factors may contribute differently to the final score |
| Is the company compared with peers? | Some ratings are relative to industry or sector performance rather than an absolute benchmark |
| When was the rating last updated? | Recent improvements, controversies or changes in disclosure may not yet be reflected |
The main takeaway here is that the rating is the starting point.
The methodology explains what it actually means.
That also makes transparency key. If investors and companies cannot see how a provider arrived at its assessment, it becomes much harder to compare ratings or understand why they differ.
This is one reason regulators are now placing greater scrutiny on how ESG rating methodologies are designed and disclosed.
ESG rating methodologies are becoming more transparent
The lack of consistency between ESG ratings has attracted regulatory attention in the EU.
Since 2 July 2026, the EU ESG Ratings Regulation has applied to providers operating in the EU. One of its main aims is to make ESG ratings easier to understand by requiring greater transparency around how they are produced.
Providers must disclose:
- The methodologies, models and key assumptions used
- The rating’s objective, including whether it assesses ESG risks, impacts or both
- The ESG topics covered and, for aggregated ratings, how E, S and G are weighted
- Data sources, estimation methods and how frequently data is updated
- Whether the rating is absolute or relative, including any peer or industry benchmarking
- Limitations in the methodology or available data
- The use of AI in data collection or rating processes, where applicable
- Potential conflicts of interest and how they are managed
- More detailed information for rating users and rated companies on data quality controls, methodology changes and the reasons ratings may change
The detailed rules also require providers to explain limitations in the data and methodology, including the use of estimates, assumptions or proxies.
For companies, this places more value on having ESG and sustainability data managed in a consistent, traceable way. Using a single sustainability platform can help bring information from across the business together, maintain clear supporting evidence and make the same governed data available for ratings, disclosures and other stakeholder requests.
That foundation becomes especially useful when different rating providers ask different questions of the same underlying ESG performance.
Build stronger ESG foundations with Sweep
So, what can companies actually do about their ESG ratings?
The most useful thing a company can control is not the rating itself, but the quality of the data and performance behind it.
Sweep is a sustainability intelligence platform that provides a central environment for managing that information, so the same governed data can support ratings, disclosures, investor requests and wider sustainability reporting.
With Sweep, organizations can:
- Centralize sustainability data across the organization and value chain
- Upload data once and reuse it across multiple reporting frameworks
- Apply built-in validation and governance controls
- Reduce manual spreadsheets and re-keying errors
- Maintain audit-ready data from a single trusted source
- Share sustainability insights across teams to support better decisions
- Use Sweepy and its AI agents to map data, validate information and surface gaps or inconsistencies
This gives teams greater confidence in the information behind their ESG performance, while making that data useful beyond any single assessment.
Organizations can’t control how every ESG rating provider weights or interprets their performance. But they can make sure the underlying information is complete, well-governed and ready to withstand scrutiny.
Book a demo to explore how Sweep can turn your sustainability data into a trusted foundation for reporting and decision-making.
