Amazon says it does not use a simple average to calculate overall star ratings. In the Reviews from Amazon FAQ, Amazon says the overall star rating and percentage breakdown by star are calculated using several factors, including how recent a review is and whether the reviewer bought the item on Amazon.
Does Amazon say overall star ratings are just an average of review scores?
No. Amazon says in the FAQ that it does not use a simple average to calculate the overall star rating and percentage breakdown by star.
That matters because it means the visible rating is not just arithmetic. Amazon is applying a weighting or ranking model rather than displaying a raw average.
What factors does Amazon say it considers?
In the same Amazon-owned FAQ, Amazon says factors include:
- how recent a review is
- whether the reviewer bought the item on Amazon
Amazon’s Understanding Customer Reviews and Ratings help page also describes overall star ratings as being based on machine-learned models rather than a simple average.
Does Amazon explain the full weighting formula?
Not publicly. Amazon gives examples of factors it considers, but it does not publish a complete formula or exact weights in the sources above.
So the safest summary is that Amazon discloses direction, not the full math.
What is the practical takeaway from Amazon’s wording?
Amazon’s own explanation points to a simple conclusion: an overall star rating is a modeled output, not just a visible average of all submitted scores.
That is why Amazon’s guidance on recency, purchase context, and review integrity matters when people try to understand how product ratings appear on the site.