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Medicare Advantage star ratings are built from measure-level scores, then combined into summary ratings using weights that vary by measure. For the 2027 ratings, improvement measures carry the greatest weight, followed by many health-outcome measures; patient experience, complaints and access measures have lower weights, and process measures generally have the least. The 2027 ratings were published on October 8, 2026, and use data primarily from measurement year 2025.
What a Medicare Advantage star rating measures
The Centers for Medicare & Medicaid Services (CMS) rates Medicare Advantage and Part D contracts on the quality of care and services they provide. CMS first assigns stars to individual measures. It then combines applicable measure ratings into Part C and, when drug coverage is included, Part D summary ratings and an overall Medicare Advantage-Part D (MA-PD) rating.
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This is a contract-level quality measure, not a prediction of what will happen to one enrollee. A star rating does not tell you whether a particular doctor is in a plan’s network, whether a medication is covered, or whether the plan’s costs and benefits fit your needs. CMS presents quality information alongside benefits and costs in Medicare Plan Finder, so those details need to be evaluated separately.
The rating also depends on more than a plan’s reported results. The measure set, measure weights, annual performance cut points, contract type and CMS adjustments all affect the published score. That is why the calculation is best understood as a sequence rather than as a simple average of every quality result.
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How CMS calculates a rating
1. CMS gathers measure data
For the 2027 ratings, CMS identifies several sources of performance information: CAHPS surveys, the Health Outcomes Survey (HOS), HEDIS, Part C and Part D reporting requirements, and data validation. Each measure has its own data source and scoring rules; a survey measure is not necessarily calculated the same way as a clinical or administrative measure.
The 2027 ratings are for contract year 2027 and rely primarily on measurement-year 2025 data. The rating year and the year of the underlying performance data therefore are not interchangeable. A rating published for 2027 is not a snapshot of care delivered solely during 2027.
2. Measure results are converted into stars
CMS translates each measure’s performance score into a rating from one to five stars. For most measures, it uses clustering across contract scores to establish four cut points, which divide scores into five performance bands. In the 2027 methodology, CMS removes Tukey outer-fence outliers for non-CAHPS measures and uses mean resampling to estimate cut points.
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CAHPS measures use a separate approach based on relative score distributions and significance tests, including checks related to score reliability. It would therefore be inaccurate to assume that one clustering procedure sets the cut points for every measure.
CMS also uses guardrails to limit some year-to-year movement in cut points. For measures on a 0–100 scale, the stated 2027 guardrail limits movement to at most five percentage points. A guardrail moderates changes; it does not freeze the cut points or guarantee that the same raw score will receive the same stars in future years.
3. Measure stars are combined using weights
For summary and overall ratings, CMS calculates a weighted average. It multiplies each rated measure’s star value by its assigned weight, adds those products, and divides by the total weights for the measures that have ratings. Unrated measures are excluded from this calculation. Summary and overall ratings use half-star increments.
For example, a measure rated three stars with weight three contributes nine weighted star points to the numerator and three units to the denominator. A one-star measure with weight one contributes one point to the numerator and one unit to the denominator. This shows why the first measure has three times as much influence on the average as the second; it does not represent an actual plan’s results.
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The weighted average is not the only rule involved. CMS applies reward-factor, Categorical Adjustment Index, improvement-measure and rounding rules before publishing ratings. Contract types also have minimum measure requirements. The applicable rules can vary with contract type, so an MA-only contract should not be assumed to have precisely the same rating inputs as a contract that also offers Part D coverage.
Which measures carry the most weight in 2027?
For the 2027 ratings, the broad weighting order is: improvement measures first; outcome and intermediate-outcome measures next; patient-experience, complaints and access measures after those; and process measures last. The measure’s individual weight determines how strongly its star rating affects the weighted average. CMS’s measure-specific rules and exceptions still matter, so category is a guide rather than a substitute for checking an individual measure.
| Measure group or example | 2027 weight | Examples |
|---|---|---|
| Improvement | 5 | Health Plan Quality Improvement (Part C); Drug Plan Quality Improvement (Part D) |
| Outcomes and intermediate outcomes | Generally 3 | Improving or Maintaining Physical Health; Improving or Maintaining Mental Health; Diabetes Care—Blood Sugar Controlled; Controlling Blood Pressure; Plan All-Cause Readmissions; three medication-adherence measures |
| Patient experience, complaints and access | 2 | Getting Needed Care; Rating of Health Plan; Complaints about the Health Plan; appeals measures |
| Process | 1 | Breast Cancer Screening; Annual Flu Vaccine; Concurrent Use of Opioids and Benzodiazepines; Polypharmacy: Use of Multiple Anticholinergic Medications in Older Adults |
A weight of five makes a rated improvement measure count five times as much in the weighted-average calculation as a weight-one process measure, assuming both are included and rated. This is an influence on the aggregate, not a claim that one category matters more to an individual’s health or that a plan’s performance on a single measure determines its overall rating.
Weight changes that affect comparisons
CMS increased the weights for Improving or Maintaining Physical Health and Improving or Maintaining Mental Health from one in 2026 to three in 2027, following substantive specification changes. The aggregate calculation can consequently shift because of the revised weighting even if a contract’s star performance on one of these measures is unchanged. Comparing ratings across years without accounting for such changes can give a misleading impression of how much a plan’s underlying performance moved.
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The 2027 MA-PD ratings cover up to 43 unique measures; MA-only contracts cover up to 32, and standalone Part D plans cover up to 13. “Up to” matters: the applicable measures depend on contract type, and these totals do not mean that every contract is rated on every measure.
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- Concurrent Use of Opioids and Benzodiazepines and Polypharmacy: Use of Multiple Anticholinergic Medications in Older Adults were added as Part D process measures, each with weight one.
- Care for Older Adults—Functional Status Assessment returned after a substantive specification change.
- A respecified Colorectal Cancer Screening measure replaced the legacy measure.
- Improving or Maintaining Physical Health and Improving or Maintaining Mental Health increased from weight one to weight three.
- Medication Therapy Management Program Completion Rate for Comprehensive Medication Review moved to the display page for measurement years 2025 and 2026. CMS scheduled it to return as a new measure for the 2029 ratings, based on measurement year 2027.
- Care for Older Adults—Pain Assessment and Medication Reconciliation Post-Discharge were retired from the ratings.
A changed measure set can affect the basis for an overall rating even when the displayed star result looks like the same familiar one-to-five scale. A measure can be added, removed, respecified or assigned a different weight; each change alters what is being measured or how strongly it contributes.
Independent reader supportYour contribution helps us test, update, and keep practical guides available for everyone.Why a plan’s star rating can change
CMS recalculates cut points each year based on performance during the measurement period. The agency says year-to-year changes are expected. As a result, a measure’s star rating may move for several distinct reasons:
- The contract’s own performance changed.
- The distribution of scores across contracts changed, shifting the relative cut points.
- The measure’s specification, availability or place in the rating set changed.
- The measure’s weight changed, affecting its influence on summary or overall ratings.
- CMS’s methodology or applicable adjustments affected the calculation.
Guardrails can limit some cut-point movement, but they do not make cut points permanent. A stable raw score can therefore map to a different number of stars in another year if the comparison distribution or applicable rules change. Conversely, a change in an overall rating cannot by itself identify which underlying measure or calculation step caused it; the measure-level results and year-specific methodology are needed for that explanation.
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CMS reported that approximately 37% of MA-PD contracts—188 contracts—earned four or more stars for 2027. Approximately 71% of MA-PD enrollees were in contracts with four or more stars. These are figures about the 2027 rating distribution, not projections for a particular person or measures of an individual enrollee’s likely health outcome.
The overall rating is useful as a quality signal, but it compresses many measures into one summary. Two contracts with the same overall rating may have different measure-level results, and Part C and Part D performance can differ within an MA-PD contract. Looking only at the single overall number hides those distinctions.
How to use star ratings when comparing plans
- Check the rating year. Use the current rating for the plan year you are considering. For the 2027 ratings, remember that performance data are primarily from measurement year 2025.
- Separate Part C and Part D. Review the applicable summary ratings as well as the overall MA-PD result. A combined score does not show whether the contract’s medical-care and drug-plan performance are alike.
- Look at measure-level categories. Check outcomes, patient experience, access, complaints and process measures rather than treating the overall star figure as a complete description. Weights explain why the same star difference can have different influence in the aggregate.
- Account for year-to-year changes. If a rating rose or fell, compare the measure set, weights and measure-level results across the years. The overall result alone does not distinguish a performance change from a shift in cut points or methodology.
- Check practical fit separately. Verify the plan’s benefits and costs, coverage details, and whether the providers and services you need fit. A high rating cannot establish that a particular plan is right for your circumstances.
CMS published the 2027 Star Ratings on October 8, 2026. They appear in Medicare Plan Finder for 2027 Open Enrollment and affect 2028 Medicare Advantage quality bonus payments. The timing is another reason to read the rating year carefully: the published rating, the period when consumers use it, and the payment year it affects are different pieces of the timeline.
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