How does Amazon calculate the star rating?

According to Amazon's customer help page it is not a simple average but machine-learned models that weigh recency and verified purchase. Ratings without a verified purchase are not counted until text, an image or a video is added (read on 2026-09-26).

Then what is this calculation good for?

It gives the order of magnitude: whether you are 10 or 200 ratings away and how heavy one 1★ is. It is a planning gauge, not the exact star.

⭐Rating Calculator

How many ratings to your target?

Enter your current average, rating count and target: see the extra ratings you need, how far one 1★ pulls the average down and how many new ratings win it back. We also say plainly that Amazon does not use a simple average.

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Free — no signup needed

Example: 4.2 → 4.5 (57 ratings)

4.14

Average after one 1★

5★ to win back one 1★

sellerniche.com/dashboardPREVIEW

⭐Rating CalculatorOVERVIEW

Extra 5★ needed35

After one 1★4.14

To win back a 1★4

Sample view — your own data after sign-inSeller Niche

Rating Goal Check

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Current average rating (1–5)

Current number of ratings

Target average (1–5)

Average of the new ratings · 5 = all five-star; try 4.6–4.8 for a realistic mix

ⓘ Rounding: money lines are rounded to the nearest cent, and the total on screen is the sum of the lines on screen. The marketplace's own rounding can differ by a cent per line; in tiered rate cards the direction of that difference is not guaranteed.

Extra ratings needed for 4.5 (averaging 5.0)35

Total ratings once the target is reached

Average after a single 1★

4.14

New ratings needed to win back one 1★

⚠️ Amazon does NOT use a simple average: its own help page says it uses "machine-learned models", weighing how recent a rating is and whether it is a verified purchase. Ratings without a verified purchase are not counted until text, an image or a video is added. This is a simple-average roadmap; the star on the product page can differ.

Source: Amazon customer help, "Understanding Customer Reviews and Ratings" (read on 2026-09-26). One 1★ weighs far more when you have few ratings.

Carry this calculation into your dashboard

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Inputs are stored only in your browser, and the link carries the calculation itself.

The problem

A rating goal without a number is a wish.

How many reviews is 4.3 to 4.5, and how many weeks of work does one 1★ erase? Most sellers plan campaigns without knowing.

📉

One 1★ hits hard early

At 57 ratings, one 1★ takes several 5★ to undo; the screen gives the exact number.

🎯

Some targets are impossible

If new ratings average below the target, the average never gets there however many arrive — the tool says so.

🤖

Amazon is not a simple average

Amazon's own page: stars come from machine-learned models that weigh recency and verified purchase. The math is a roadmap.

Features

Target, buffer and the 1★ effect.

➕

Extra ratings needed

You also choose what the new ratings average: all 5★ or a realistic mix.

🛡️

Buffer once you are there

If you are above target, it shows how many 1★ you can absorb before dropping below.

↩️

Winning back a 1★

The average after a single 1★ and the new ratings that bring it back.

📥

Link and CSV

Share the result with a link or download a CSV with the inputs included.

How it works?

1️⃣

Enter where you are

The average and the count are on the product page.

2️⃣

Pick the target

For example 4.5; keep the new-rating average realistic.

3️⃣

See the roadmap

Ratings needed, buffer and the 1★ effect on one screen.

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Frequently Asked Questions

Plan your rating with a number.

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