Five Star Rating Calculator

Enter how many 1, 2, 3, 4, and 5-star reviews you received to get the exact average star rating, weighted by how many reviews fall at each level.

Quick Facts

Method
Weighted mean: Σ(stars × count) ÷ total reviews
The same formula Amazon, Google, and Yelp use to show an overall star score.

Your Results

Calculated
Average star rating
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Weighted mean (0-5)
Total reviews
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Sum of all counts
Sum of stars
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Σ(stars × count)
% positive (4-5 star)
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Share of favourable reviews

Ready

Enter your review counts and press Calculate.

How the average star rating is calculated

An overall star rating is a weighted mean. You take each star level (1 through 5), multiply it by how many reviews gave that number of stars, add all five products together, and divide by the total number of reviews:

Average = (1×n1 + 2×n2 + 3×n3 + 4×n4 + 5×n5) ÷ (n1 + n2 + n3 + n4 + n5)

Here n1 is the count of 1-star reviews, n5 the count of 5-star reviews, and so on. This is exactly the formula that Amazon, Google, Yelp, Trustpilot, and the App Store use to turn a pile of individual ratings into the single number shown next to the stars.

A worked example

Suppose a product has 120 five-star, 45 four-star, 18 three-star, 7 two-star, and 10 one-star reviews. The numerator is (5×120) + (4×45) + (3×18) + (2×7) + (1×10) = 600 + 180 + 54 + 14 + 10 = 858. The total number of reviews is 120 + 45 + 18 + 7 + 10 = 200. So the average is 858 ÷ 200 = 4.29 stars. That is why the average is rarely a whole number: it is the balance point of the whole distribution, not any single rating.

Why the rating is needed

A single average condenses hundreds or thousands of opinions into one comparable figure. Shoppers scan it to decide in seconds; search engines and marketplaces use it to rank and filter products; and businesses track it over time as a satisfaction metric. Because it is a mean, it responds smoothly to new reviews — one extra 5-star review nudges a 4.29 up slightly, while a fresh 1-star review pulls it down.

Common reference points

  • 4.5–5.0 — Excellent. Most listings that display "top rated" badges sit here.
  • 4.0–4.4 — Strong. Widely trusted; research on marketplaces suggests conversions often peak in the 4.0–4.7 band because a perfect 5.0 can look suspicious.
  • 3.0–3.9 — Mixed. Enough negative reviews to give buyers pause.
  • Below 3.0 — Poor. Signals widespread dissatisfaction.

Note that a 5.0 average requires every single review to be 5 stars; a single 1-star review among 20 otherwise perfect ratings drops the average to (5×19 + 1) ÷ 20 = 96 ÷ 20 = 4.8.

Frequently Asked Questions

How is the average star rating calculated?
Multiply each star level by the number of reviews at that level, add the five products together, and divide by the total number of reviews. For 10 five-star and 5 three-star reviews: (10×5 + 5×3) ÷ 15 = 65 ÷ 15 = 4.33 stars.
Why isn't my average a whole number?
The average is a weighted mean, so it almost always falls between whole star values. A store showing 4.6 stars simply has a mix of ratings whose mean works out to 4.6 — no reviewer actually gave 4.6 stars. Sites typically round the display to one decimal place.
Does a higher number of reviews change the average?
Only through the counts themselves. More reviews make the average more stable (harder to move with one new rating), but the formula treats every review equally regardless of the total. Some sites layer a Bayesian or "true Bayesian" adjustment on top so that items with very few reviews are pulled toward the site-wide average; this calculator reports the plain, unadjusted mean.
What's the difference between the average and the median rating?
The average (mean) accounts for how far apart the ratings are, so a cluster of 1-star reviews drags it down noticeably. The median is just the middle rating when they're sorted and ignores magnitude. Star ratings almost always use the mean because it reflects the full spread of opinion.

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