"How many 5-star reviews do I need to get from 4.2 to 4.5?" is one of the most common questions local business owners ask, and the honest answer is: it depends entirely on how many reviews you already have. Here's the math behind it, and a simple way to estimate your own number.
The formula
Google's star rating is just an average of every review you've ever received, so the calculation is:
New average = (current total stars + new review stars) ÷ (current review count + new review count)
The current total stars is your existing rating multiplied by your existing review count. From there you can solve for how many 5-star reviews it takes to reach a target average.
A worked example
Say you have 80 reviews at a 4.2 average. That's roughly 336 total stars. To reach 4.5, you'd need enough new 5-star reviews that (336 + 5x) ÷ (80 + x) = 4.5. Solving that gives roughly 96 new 5-star reviews — which feels like a lot until you realize it's happening on top of your existing base, not from zero.
Why review count matters more than most owners expect
The lower your current review count, the faster your rating moves. A business with 10 reviews can shift its average significantly with just 5-10 new 5-star reviews. A business with 500 reviews needs a much larger volume to move the needle at all — which is exactly why review velocity (reviews per month) matters more as you grow, not less.
Rough milestones to work from
- Under 20 reviews: 5-10 new 5-star reviews can meaningfully shift your average
- 20-100 reviews: expect to need 20-40+ new reviews to move half a star
- 100-500 reviews: consistent monthly review flow matters more than any single push
- 500+ reviews: focus shifts from "raising the average" to "maintaining volume and freshness"
Don't chase the number at the expense of the process
It's tempting to treat this as a target to hit as fast as possible, but Google actively penalizes unnatural review spikes and can flag or remove reviews that look incentivized or fake. The safest path is steady, ongoing collection — a QR code at checkout, a link in your WhatsApp follow-up, a mention at the register — rather than a single burst campaign.
The bottom line
Your target review count depends on your current base, not a fixed number that applies to every business. Run the math for your own numbers, but treat the result as a pace to sustain over months, not a sprint — that's both safer for your account and more realistic for most local businesses.