How Much Does One 1-Star Review Really Hurt You?
One 1-star review can knock a small business from a 4.8 down to a 4.5. The same review barely moves a business with 100 reviews. The difference isn’t the review. It’s how many reviews are standing next to it.
Your star rating is an averaging game. Every review is one vote, and a bad one pulls the average down by an amount that depends on how many other votes there are. That makes your review count your shock absorber.
How Google calculates your star rating
Google’s help page for business owners says your review score is the average of all ratings published on Google for your business. It also says an updated score can take up to two weeks to show after a new review comes in.
What Google doesn’t spell out is how it rounds that average to the one decimal you see, or exactly which reviews count at any given moment (filtered or removed reviews don’t). So a simple average, rounded to one decimal, is a close approximation of what you’ll see. That’s what we use below.
The formula is just:
Rating = total stars ÷ number of reviews
One 1-star review, four different businesses
Here’s what a single 1-star review does to four businesses. “Total stars” is every rating added together.
| Starting point | Total stars before | After one 1-star | Exact average | What shows on Google |
|---|---|---|---|---|
| 10 reviews, all 5-star (5.0) | 50 | 51 ÷ 11 | 4.636 | 4.6 |
| 100 reviews, all 5-star (5.0) | 500 | 501 ÷ 101 | 4.960 | 5.0 |
| 10 reviews averaging 4.8 | 48 | 49 ÷ 11 | 4.4545 | 4.5 |
| 100 reviews averaging 4.8 | 480 | 481 ÷ 101 | 4.762 | 4.8 |
Look at the third row closely. 49 ÷ 11 = 4.4545..., which rounds to 4.5 at one decimal place. But it’s sitting right on the edge. It’s only a hair above 4.45, the line where normal rounding flips down to 4.4. One more 4-star review would put that business at 53 ÷ 12 = 4.42, which shows as 4.4.
Now compare the rows in pairs. The 10-review business lost four tenths of a star off its displayed 5.0. The 100-review business lost nothing you can see. Same customer, same complaint, very different damage.
Why those tenths of a star matter
BrightLocal’s 2026 consumer survey found that 31% of consumers will only use a business rated 4.5 stars or higher. 68% will only use a business with 4 stars or more. And negative reviews deter 77% of consumers from using a business.
So that third business in the table, now hanging on at 4.5 by a thread, is one mediocre review away from dropping below the line almost a third of shoppers use. A business with a deep pile of reviews doesn’t have that problem.
How many 5-star reviews does it take to recover?
People search for a “Google review calculator” to answer this. Every one of those calculators runs one formula. Here it is, so you can do it on your phone.
To reach a target rating T, when you currently have S total stars across N reviews, the number of new 5-star reviews you need is:
n ≥ (T × N − S) ÷ (5 − T)
Round up to the next whole number. You can’t get half a review.
Example 1: back to a 4.8
Take the first business from the table. It had 10 five-star reviews, then got one 1-star. Now it has 51 stars across 11 reviews. How many 5-star reviews to get back to a true 4.8?
- T × N = 4.8 × 11 = 52.8
- 52.8 − 51 = 1.8
- 5 − 4.8 = 0.2
- 1.8 ÷ 0.2 = 9 reviews
Check: 51 + (9 × 5) = 96 stars. 11 + 9 = 20 reviews. 96 ÷ 20 = 4.8.
Example 2: the business on the edge
Now the third business: 49 stars across 11 reviews, showing 4.5. How many 5-star reviews to get back to a true 4.8?
- T × N = 4.8 × 11 = 52.8
- 52.8 − 49 = 3.8
- 3.8 ÷ 0.2 = 19 reviews
Check: 49 + (19 × 5) = 144 stars. 11 + 19 = 30 reviews. 144 ÷ 30 = 4.8.
Nineteen reviews to undo one bad day. That’s the real cost of a thin review count.
So how many 5-star reviews cancel out a 1-star?
Strictly speaking, none. Once a 1-star is in the average, your true rating can never be exactly 5.0 again unless that review is removed.
What you can do is get back to displaying 5.0. Assuming normal rounding, that takes a true average of 4.95 or better. Using the formula on the first business (51 stars, 11 reviews): (4.95 × 11 − 51) ÷ 0.05 = (54.45 − 51) ÷ 0.05 = 3.45 ÷ 0.05 = 69 more 5-star reviews. That’s 80 reviews in total: 79 five-star reviews holding up that single 1-star (396 ÷ 80 = 4.95).
In practice, most owners are better off aiming for a strong 4.8 or 4.9 than chasing a perfect 5.0. BrightLocal’s survey found only 10% of consumers require 5 stars.
What to do when a 1-star review shows up
1. Reply, calmly. Wait until you’ve cooled off. Thank them, acknowledge the problem without arguing the details in public, and offer a way to talk it through offline. Future customers will see your reply right under the review. Our guide on how to respond to Google reviews has examples.
Example reply: “Hi Dana, thanks for taking the time to share this. I’m sorry the visit didn’t go the way you expected. I’d like to make it right. Please call me directly at the office so we can talk it through.”
2. Report it only if it actually breaks Google’s rules. Fake reviews, reviews from people who were never customers, and spam can be flagged. A review you simply disagree with usually won’t come down. See what Google will and won’t remove before you spend time on it.
3. Keep asking every customer. This is the real fix. The formula only works if new reviews keep coming in. Ask every customer, the same way, soon after the job, by text or email with a direct link. Don’t only ask the ones you think are happy. Google’s policies don’t allow selectively asking for positive reviews, and it doesn’t work anyway: a steady flow of honest reviews is what absorbs the occasional bad one. A free Google review link generator makes the link part easy.
If you have fewer than 20 or so reviews, every one carries a lot of weight. Build your count now, before you need the cushion. For what to aim for, see how many Google reviews you need.
Frequently asked questions
How many 5 star reviews to cancel a 1 star on Google?
Your true average can’t return to exactly 5.0 while the 1-star is there. To display 5.0 again, assuming normal rounding, you need a true average of at least 4.95. That works out to 79 five-star reviews alongside the one 1-star (80 total). Getting back to 4.8 takes far fewer.
How many 5-star reviews does it take to increase Google rating?
Use this formula: n ≥ (T × N − S) ÷ (5 − T), where T is your target rating, N is your current review count, and S is your total stars. Round up. For example, going from 49 stars over 11 reviews to a 4.8 takes 19 five-star reviews.
How many 5-star reviews do I need to increase my rating?
It depends on how many reviews you already have. A business with 11 reviews can move a lot with a handful of new ones. A business with 100 needs many more to move the same amount, but it also drops much less when a bad one comes in.
How much does one bad review affect my Google rating?
With 10 perfect reviews, one 1-star drops you from 5.0 to 4.6. With 100 perfect reviews, it barely moves you (4.96, which still shows as 5.0). Your review count decides how much it hurts.
The short version
- Your Google rating is basically total stars divided by number of reviews. Google says it’s an average but doesn’t publish how it rounds.
- One 1-star review hurts a lot when you have 10 reviews and barely registers when you have 100.
- To find how many 5-star reviews you need: n ≥ (T × N − S) ÷ (5 − T), rounded up. That’s all a “Google review calculator” does.
- 31% of consumers only use businesses rated 4.5+, so small drops can cost real calls.
- Reply calmly, report only real policy violations, and keep asking every customer.
Rather not do this yourself? ReviiewCo handles asking every customer for a Google review for home service businesses, done for you. See how it works.
Sources
Rob Warfield is the founder of ReviiewCo, based at 403 Woods Lake Rd Ste 100 in Greenville, SC. He has spent more than twenty years as an entrepreneur in real estate and in building businesses of his own. More about Rob.