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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.

Current rating

Number of reviews

Target rating

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.

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Put this calculator on your site

Copy the code below — it works anywhere, and links back here.

<iframe src="https://reputemap.com/tools/embed/review-rating-calculator" width="100%" height="300" style="border:1px solid #e5e5e5;border-radius:12px;max-width:520px" title="Google Star Rating Calculator" loading="lazy"></iframe>
<p style="font:13px/1.5 -apple-system,sans-serif;text-align:center;margin:8px 0 0"><a href="https://reputemap.com/tools/review-rating-calculator">Google Star Rating Calculator</a> by <a href="https://reputemap.com">ReputeMap</a></p>

Get to your target rating faster

ReputeMap asks every customer for a review by email + QR (honestly, no gating) and alerts you on negatives — so your rating climbs the right way.

Start free trial →

Frequently asked questions

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.