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Google Review Calculator: How Many 5-Star Reviews Do You Need?
A Google review calculator works out how many new 5-star reviews it takes to reach a target rating. The formula is x = n × (target − rating) ÷ (5 − target), where n is your review count. A practice with a 4.5 rating on 100 reviews needs 100 more 5-star reviews to show 4.8. Enter your numbers below to see yours, plus what one 1-star review does.
Prepared by Prospyr · Reviewed October 3, 2026 · Free, no sign-up, runs in your browser
As shown on your Google profile, such as 4.5.
Adds a time estimate from your own pace.
5-star reviews needed to reach 4.8
100reviews
Your rating would become 4.8 (4.75 unrounded) across 200 reviews.
One 1-star review lands you at
4.47
down 0.03
5-stars to win it back
7
Back to your current average
Assumes Google shows a simple average of star ratings to one decimal; Google does not publish its exact method and can remove reviews. Ask for reviews, never pay or discount for them.
Google rating calculator formula and worked example
A star rating is an average. Your current rating times your review count gives the total stars you hold. Each new review adds its stars to the total and 1 to the count.
- New average: (rating × n + star × x) ÷ (n + x)
- Reviews needed: x = n × (target − rating) ÷ (star − target), rounded up
Worked example. Your profile shows 4.5 on 100 reviews, so you hold 450 stars. A badge displays one decimal, so 4.8 appears once the average is 4.75 or higher. x = 100 × (4.75 − 4.5) ÷ (5 − 4.75) = 100. Check it: (450 + 500) ÷ 200 = 4.75. The calculator above does this for any rating, any count and either 5-star or 4-star new reviews.
How many 5-star reviews you need, by rating and review count
Whole 5-star reviews needed for the rating to show the target, counting 4.75 as 4.8 and so on. Counts grow fast as your total grows.
| Rating to target | 25 reviews | 50 reviews | 100 reviews | 250 reviews | 500 reviews |
|---|---|---|---|---|---|
| 4.0 to 4.5 | 21 | 41 | 82 | 205 | 410 |
| 4.3 to 4.5 | 7 | 14 | 28 | 69 | 137 |
| 4.5 to 4.8 | 25 | 50 | 100 | 250 | 500 |
| 4.7 to 4.9 | 25 | 50 | 100 | 250 | 500 |
| 4.5 to 5.0 | 225 | 450 | 900 | 2,250 | 4,500 |
The practical takeaway: a newer profile moves quickly, and a profile with hundreds of reviews moves slowly in both directions. If you keep a steady monthly pace, put your own number in the calculator for a timeline.
What one 1-star review does to your Google rating
One 1-star review lowers the average by (rating − 1) ÷ (n + 1). With few reviews that is large; with many it fades.
| Starting rating | After one 1-star on 25 | After one 1-star on 50 | After one 1-star on 100 | After one 1-star on 250 |
|---|---|---|---|---|
| 4.9 | 4.75 (shows 4.8) | 4.82 (shows 4.8) | 4.86 (shows 4.9) | 4.88 (shows 4.9) |
| 4.7 | 4.56 (shows 4.6) | 4.63 (shows 4.6) | 4.66 (shows 4.7) | 4.69 (shows 4.7) |
| 4.5 | 4.37 (shows 4.4) | 4.43 (shows 4.4) | 4.47 (shows 4.5) | 4.49 (shows 4.5) |
To get back to the exact prior average you need (rating − 1) ÷ (5 − rating) five-star reviews. That is 7 at 4.5, 13 at 4.7 and 39 at 4.9, and it does not depend on how many reviews you started with.
Getting more reviews without breaking Google's rules
Google allows asking customers for reviews with a link or QR code. Its Business Profile help states that offering free or discounted goods or services in exchange for reviews is prohibited, and its Maps content policy says businesses should not pressure people to leave ratings while on the premises or request specific content. Rewarding only positive reviews, or discouraging negative ones, is also a violation. Do not offer incentives.
A routine that works for a practice: send every patient a review link after the visit, on the same schedule, and reply to every review, good or bad, without including health details. Prospyr's online reputation management sends the request after checkout and tracks replies, and the med spa software page shows how that fits with scheduling and follow-up.
Frequently asked questions
How many 5-star reviews do I need to raise my Google rating?
Use x = n × (target − rating) ÷ (5 − target), rounded up. At 4.5 stars on 100 reviews, you need 100 five-star reviews to show 4.8, because the average must reach 4.75 to round up. The more reviews you already have, the more it takes, so a practice with 500 reviews needs 500 for the same move.
How many 5-star reviews to get from 4.5 to 5.0?
Showing 5.0 means the average must reach 4.95, which takes 900 five-star reviews at 100 existing reviews. An exact 5.00 average is impossible once any lower rating is in the mix, because 5-star reviews only move the average toward 5. Aim for 4.8 or 4.9; that is a realistic target for a well-run practice.
How does Google calculate the star rating?
Google does not publish its exact method. The usual assumption, and the one this calculator makes, is a simple average of all star ratings shown to one decimal place. Google can remove reviews that break its policies, so the number on your profile can differ from your own count.
How much does one 1-star review hurt my rating?
It depends on how many reviews you have. At 4.9 on 25 reviews, one 1-star lowers the average to 4.75. At 4.5 on 100 reviews it drops to 4.47. To recover the exact prior average you need (rating − 1) ÷ (5 − rating) five-star reviews, which is 7 at 4.5.
Can I offer a discount or gift for a Google review?
No. Google's Business Profile help says offering incentives such as free or discounted goods or services in exchange for reviews is prohibited. You can ask patients to leave a review with a link or QR code, but you cannot pay for them or discount a visit in return.
How do I ask patients for Google reviews the right way?
Ask every patient, after the visit, with a direct review link or QR code. Google's policy says businesses should not pressure people to review while on the premises or ask for specific content. Send the request by text or email a day or two later and keep it the same for everyone.
Does this work for star ratings on other sites?
Yes. The math is a plain weighted average, so it works for any 5-star scale, such as Yelp or Facebook. Only the display rounding differs by site, so untick the rounding box to use the exact average.
Sources and scope
- Tips to get more reviews. Google Business Profile Help
Says customers can be asked to leave reviews via a link or QR code, and that offering incentives for reviews is prohibited.
- Prohibited & restricted content. Maps User Generated Content Policy Help
Lists incentivized reviews as prohibited and says businesses should not pressure customers to review on the premises or request specific content.
Arithmetic on a simple average. Google does not publish how it computes or displays ratings and may remove reviews, so your profile can differ. Follow Google's current review policies.