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Google Star Rating Calculator
How many new 5-star reviews do you need to hit your target rating? Enter your numbers and find out instantly.
How many 5-star reviews cancel out a 1-star review?
At a 4.5★ average, 7. To get back to your average A after one 1★ review, you need n = (A − 1) ÷ (5 − A) new 5★ reviews, rounded up, however many reviews you already have. The 1★ review sits A − 1 stars below your average, each new 5★ review sits 5 − A stars above it, and the two have to balance.
| Your average before the 1★ review | n, exact | New 5★ reviews to get back |
|---|---|---|
| 4.0★ | 3 | 3 |
| 4.2★ | 4 | 4 |
| 4.5★ | 7 | 7 |
| 4.7★ | 12.33 | 13 |
| 4.8★ | 19 | 19 |
| 4.9★ | 39 | 39 |
Google shows your average rounded to one decimal, so with many reviews a single 1★ may not change the number customers see at all. The table is for the exact average.
Assumes new reviews are 5★. Updates as you type.
You need about 24 new 5★ reviews to go from 4.2★ to 4.5★.
That takes you to 4.50★ across 64 reviews. At ~2 new reviews a week, that's about 12 weeks.
How the math works
Your Google rating is the simple average of every review's star value. To go from rating r across n reviews to a target rating t with new 5-star reviews, you need x = ⌈n·(t − r) / (5 − t)⌉ new reviews. Worked example: a business at 4.2★ with 40 reviews needs about 24 new 5-star reviews to reach 4.5★ — because 40 × (4.5 − 4.2) / (5 − 4.5) = 24. The closer your target is to 5.0, the steeper the climb: the same business would need 120 new 5-star reviews to reach 4.8★.
The takeaway: the earlier you start collecting reviews consistently, the cheaper every 0.1★ becomes. Our guide to getting more Google reviews covers the honest, FTC-compliant way to do it, and review request software can automate the asking by email and QR code. If your rating just fell and you want to know why, the rating drop checker shows what pulled it down.
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Start free trialFrequently asked questions
How many 5-star reviews cancel out a 1-star review?
Divide the gap between your average and 1 by the gap between 5 and your average: n = (A − 1) ÷ (5 − A), rounded up. At 4.0★ that's 3 new 5-star reviews, at 4.2★ 4, at 4.5★ 7, at 4.7★ 13 and at 4.8★ 19, however many reviews you already have.
How is a Google star rating calculated?
Your rating is the simple average of every review's star value. So 40 reviews averaging 4.2 means the total stars = 168; adding ten 5-star reviews makes it 218 stars over 50 reviews = 4.36. This tool does that math for your target.
How many 5-star reviews do I need to go up 0.1?
It depends on how many reviews you already have — the more you have, the more new ones each 0.1 costs. Enter your numbers above to see the exact count for your business.
What's the fastest way to get those reviews?
Ask every happy customer, right after a good experience, with a one-tap link. ReputeMap automates that with email + QR review requests and alerts you on any negative one — start a free trial.