Free Amazon FBA tool
Amazon Review Calculator
See how many 5-star reviews lift your rating and the pace you need to catch a competitor. Review velocity, rating math, and a rating forecast.
287 reviews · 4.5★ · +9/mo · +3%/mo
Results
Review goalmonth 19
Month 14 if sales take off, month 24 if they stay flat.
Rating goalnever
At a 4.38★ incoming average you lose your 4.5★ display around month 18. Cut your 1★ share to 3% and you'd settle at 4.5★ instead.
Catch rival+102/mo
That's about 3,400 units/mo at your 3% review rate. At your current pace, parity waits until ≈ month 88.
What to do next
- Cut your 1★ share from 6% to 3% by fixing the top complaint: you'd settle at 4.5★ instead of 4.4★.
- Lift your review rate from 3% to 4% with Request-a-Review and inserts: 500 reviews by month 15 instead of 19.
- Catching them in 1 year is a sales target: +102 reviews/mo ≈ 3,400 units/mo.
Review velocity, rating math, and catching up
It answers three questions on one timeline. How many reviews you will have over the next 36 months under different sales trends. How many 5-star or 1-star reviews move your displayed rating to any 0.1★ milestone. And when, or at what pace, you would catch a competitor's review count. It is free, runs entirely in your browser, and needs no account.
Your velocity is monthly orders × review rate. At a 3% review rate, 300 orders adds about 9 reviews a month. Because orders usually grow, velocity compounds. The pace you have today understates where you will be in a year.
Between 1% and 3% of Amazon buyers leave a review, or 1 review per 33 to 100 orders. Great inserts, the Request-a-Review button, and Vine push you toward the top of that range. Doubling the rate doubles your velocity without selling one extra unit, which makes it the cheapest lever you have. The calculator defaults to 3% and lets you test 0.5% to 10%.
Your displayed rating is a weighted average rounded to 0.1★. So a displayed 4.5★ means pushing your true average to at least 4.45. From 100 reviews at 4.0★ that takes 82 consecutive five-star reviews. The price scales with your base: at 1,000 reviews it is 819. Rating inertia grows as you grow. The calculator solves this for any starting point and any 0.1★ target, in both directions.
Far fewer than it took to earn it. The climb scales with your entire review base, but the fall does not. The same 100-review listing that needs 82 five-star reviews to reach 4.5★ loses that display after only 2 one-star reviews. Your cushion, the number of bad reviews you can absorb, is worth knowing before a bad batch ships.
Your rating converges toward the average star of your incoming reviews, and that is the ceiling. If incoming reviews average 4.4★, your rating approaches 4.4★ and never displays 4.5★, no matter how many reviews arrive. The target stays out of reach until the product itself improves, so fix the mix before scaling the velocity. When that happens the calculator names the incoming average you would need instead of pretending volume will fix it.
Catch-up is gap ÷ closing speed: a 1,000-review gap closes in 20 months at +50 a month net. To estimate a competitor's velocity, divide their review count by the listing's age in months. So 1,200 reviews on a 40-month-old listing averages +30 a month. That is a lifetime average that established listings often beat today. Treat it as a floor and test a faster pace too. If your velocity is below theirs the gap only widens. The calculator then flips to the velocity you would need. That is a sales-volume target, since velocity is orders × rate.
It models the arithmetic mean of your reviews. Amazon's displayed rating is a weighted model, where recency and verified purchases weigh more. It also assumes reviews land the same month as their orders. Direction and rough magnitude are reliable; the exact month is not a guarantee. Treat it as a planning tool, not a promise.