How the estimate works
Google says its review score is the average of all ratings published for a place or business. Multiply each star value by its count, add those star points, and divide by the total number of published ratings. For the example inputs—5 one-star, 3 two-star, 8 three-star, 34 four-star, and 50 five-star ratings—there are 100 ratings and 421 star points. The exact average is 4.21.
To estimate additional five-star ratings needed for an exact target, solve (existing star points + 5 × new ratings) ÷ (existing rating count + new ratings) ≥ target. At a target of 4.50, the example requires 58 new five-star ratings; the resulting exact average is 4.50. If the current exact average already meets the target, the result is zero.
Exact average is not the displayed score
This calculator uses the star counts you provide and an unrounded target. A public Google rating may be rounded, may include a different set of published reviews than your notes, and may update later. Google says a new review can take up to two weeks to affect the displayed review score. A goal of an exact 5.00 is not achievable by adding reviews if any existing published rating is below five stars; the tool therefore accepts exact targets below 5.00.
Improve customer experience, not just the number
Ask customers for genuine feedback without offering an incentive or screening for positive experiences. Reply constructively to both positive and negative reviews and address recurring service problems. Google prohibits incentives for posting, changing, or removing reviews. The scenario above is for planning and understanding an average, not a recommendation to manipulate a profile.
Google Business Profile: understand review scores · Google: tips and rules for getting reviews