Average Rating Calculator: Star Rating from Review Counts and Reviews Needed to Reach a Target
Work out your average star rating from the number of 5, 4, 3, 2 and 1-star reviews, and how many new reviews you need to reach a target such as 4.5 stars.
How it works
Average rating = (5 × n₅ + 4 × n₄ + 3 × n₃ + 2 × n₂ + 1 × n₁) ÷ (n₅ + n₄ + n₃ + n₂ + n₁) · Reviews needed k = (T × N − S) ÷ (r − T), rounded up, where N = reviews so far, S = total stars, T = target and r = the rating of each new review (5 by default)
A star rating is a weighted average: each star level is multiplied by how many reviews gave it, the products are added to get the total stars, and the total is divided by the number of reviews. Enter your counts from the review breakdown that most platforms show, or switch to “Current average” if you only know the rating and the number of reviews. To reach a target T, the new total stars divided by the new number of reviews has to be at least T: (S + r × k) ÷ (N + k) ≥ T. Solving for k gives (T × N − S) ÷ (r − T), rounded up to a whole review. The calculator assumes 5-star reviews by default; under More options you can set a more realistic average for new reviews, which can raise the number sharply, and tell it to count a displayed (rounded) rating, since sites that show one decimal display 4.45 as 4.5. It also shows how many 1-star reviews would pull you back below the target, and what one more 5-star or 1-star review does. This is the plain mean that most stores and map listings show. Some platforms weight recent or verified reviews or use their own scoring, so their figure can differ slightly. Unlike a general weighted-mean calculator, this page is built around star counts and review targets.
Worked example
A product has 62 five-star, 18 four-star, 6 three-star, 4 two-star and 10 one-star reviews. Total stars = 5 × 62 + 4 × 18 + 3 × 6 + 2 × 4 + 1 × 10 = 310 + 72 + 18 + 8 + 10 = 418 from 100 reviews, so the average is 418 ÷ 100 = 4.18 (shown as 4.2). 80% of the reviews are 4 or 5 stars. To reach 4.5 with 5-star reviews: (4.5 × 100 − 418) ÷ (5 − 4.5) = 32 ÷ 0.5 = 64 more reviews, giving 738 ÷ 164 = 4.500. One more 5-star review would lift the average to 4.188; one more 1-star review would drop it to 4.149.
Sources: Cloutly: Google review calculator (90 reviews at 4.2 to 4.5 worked example) · Growave: Google review calculator (120 reviews at 4.4 to 4.7 example)
Frequently asked questions
How do you calculate an average star rating?
Multiply each star level by its number of reviews, add the results and divide by the total number of reviews. For 8 five-star, 1 four-star and 1 one-star review: (40 + 4 + 1) ÷ 10 = 4.5.
How many 5-star reviews do I need to get to 4.5?
Use k = N × (4.5 − current) ÷ (5 − 4.5). With 90 reviews at 4.2 you need 90 × 0.3 ÷ 0.5 = 54 more 5-star reviews. If new reviews average 4.7 instead of 5, you need 135.
Why does my rating barely move after a new 5-star review?
Each new review is only one vote among all your past reviews. With 100 reviews at 4.18, a 5-star review adds 0.82 ÷ 101 ≈ 0.008 to the average. The more reviews you have, the slower the average moves in either direction.
Can I ever reach a 5.0 rating?
Only if every review is 5 stars. Once you have a single lower review, the average can get very close to 5 but never equal it.
Does a 4.45 show as 4.5 stars?
On sites that round to one decimal, yes: 4.45 and above displays as 4.5. Turn on the rounding option under More options to count the displayed rating; it lowers the number of reviews you need.
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This calculator is for educational purposes. Double-check important results before acting on them.