(4.65 × 1000 − 4000) ÷ (5 − 4.65), rounded up = 1858
Start with 4000 star points across 1000 reviews. Each new five-star review adds 5 points and one review. Solve for an average of at least 4.65, then round up to a whole review. This threshold assumes conventional rounding to one decimal place.
Two questions. One calculator.
Enter exact star counts or an estimated average and total. Choose a target to find the minimum number of additional five-star reviews, including the difference between actual and displayed ratings.
With 100 reviews averaging exactly 4.2, reaching an actual 4.5 takes 60 additional five-star reviews.
New reviews = total × (target − average) ÷ (5 − target), rounded up
A displayed target of 4.5 assumes an average of at least 4.45. In this example, that takes 46 five-star reviews.
Start with those same 100 reviews at 4.2. Add ten five-star and three one-star reviews: the new average is 473 ÷ 113 = 4.186, still displayed as 4.2 with one-decimal rounding.
Projected average = (existing star points + new star points) ÷ total reviews
If your scenario lowers the average, the result also shows how many additional five-star reviews would restore it.
Compare all rating methods. Within this calculator, choose a target or simulate how new reviews change your rating.
Google Maps describes its score as the average of published ratings. Arithmetic mean models that calculation; displayed rounding here is an assumption.
Trustpilot includes a prior of seven reviews at 3.5 stars and also considers review age. Our Bayesian estimate models a fixed prior only, so it is not an exact TrustScore calculator.
Amazon considers recency and purchase verification. IMDb uses undisclosed weights on a 1–10 scale. Their full ratings cannot be reconstructed from five star-count totals.
Bayesian rating = (raw star points + prior weight × prior rating) ÷ (real reviews + prior weight). Both methods support targets and simulated reviews. We do not connect to these platforms.
An exact 5 is impossible if any existing review is below five stars. A displayed 5.0 can be reached at an average of 4.95 under conventional one-decimal rounding.
The link contains the starting numbers and selected target or scenario. Anyone with the link can view the calculation. Editing it creates a different link; the original stays unchanged. Links contain numbers, not business names or review text.
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{{/recovery}}{{#estimated}}Estimate based on your entered average. {{/estimated}}Displayed rating assumes rounding to one decimal; platforms may use different rules.
Compare weighted averages, time decay, recent reviews, positive percentages, Wilson scores, medians and trimmed means. Each model explains its assumptions and can differ from actual service ratings.