Amazon book sales rank comparison calculator
Compare two Amazon Best Sellers Ranks and see roughly how many times more one is selling than the other — a modelled ratio, not a copy count. Best for comparing two ranks or watching one book move over time.
Get a useful result for your book
Enter the overall Amazon Best Sellers Rank — the first number in the Product Details section, not a category rank. Type the ranks in by hand; this tool never contacts Amazon.
Where this comes from. Amazon has never published how many copies a rank equals, and no tool has access to sales figures for books it does not own. This calculator uses only the shape of the relationship between rank and sales — a power law first fitted to Amazon's print catalogue in academic work published between 2000 and 2003 — which is why it can give you the ratio between two ranks but will not give you a number of copies. Tools that do print a copies-per-day figure are supplying a constant nobody has published, which is why their figures for the same rank disagree by 50% or more.
This range is wide on purpose. The published research disagrees about how steep the curve is, and the disagreement compounds: the estimate roughly doubles or halves for every tenfold step between the two ranks you entered.
Reaching a rank takes more sales than holding it, because Amazon weights a book's entire history as well as its recent activity. A rising book is selling more than this suggests and a fading one less. This tool cannot tell which yours is.
Amazon says ranks in different formats, categories, and marketplaces are not comparable. Each is a separate pool with its own size and sales density. Do not read across them.
Not affiliated with, endorsed by, or sponsored by Amazon. Amazon, Kindle, and KDP are trademarks of Amazon.com, Inc.
Quick answerAmazon Best Sellers Rank is a relative position, not a sales count. Amazon states that rank is based on a book's customer activity relative to other books, that it weights a book's entire history with recent activity counted more heavily, and that it is not an accurate way to track a book's activity. Amazon has never published how many copies a given rank represents, so this tool compares two ranks rather than converting either one into copies.
What Amazon actually says about Best Sellers Rank
Amazon's own KDP guidance describes rank as being based on the customer activity of your book relative to the activity of other books, updated at least once a day, with changes sometimes taking up to two days to appear. Rankings reflect both recent and historical activity, with recent activity weighted more heavily, and canceled orders are not counted. Each format carries its own independent rank, and category ranks are computed differently from the overall rank. Amazon also cautions that rank is not an accurate way to track how a book is performing — a caveat worth taking literally rather than treating as boilerplate.
Why this tool will not tell you how many copies a rank sells
The relationship between rank and sales follows a power law, and the exponent of that curve has been estimated in published academic work on Amazon's catalogue — Chevalier and Goolsbee, and Brynjolfsson, Hu and Smith, among others. That research establishes the shape. It does not establish the scale: the constant that turns a position into a number of copies has never been published by Amazon for the Kindle Store, and no third party has access to sales figures for books it does not own. Every calculator that prints a copies-per-day figure has quietly supplied that missing constant itself, which is precisely why two of them will give you answers 50% apart for the same rank. The ratio between two ranks depends only on the exponent, so that is what this tool reports.
How to use a rank comparison usefully
Two ranks are far more informative than one. Comparing your book against a competitor at a known rank tells you the approximate multiple separating you, and comparing your own book against itself a week ago tells you whether a promotion actually moved anything. Treat the direction and the rough magnitude as the signal and ignore the precision. Bear in mind that reaching a rank takes more sales than holding it, because Amazon's calculation includes a book's whole history, and that a Kindle Unlimited title's rank is affected by borrows and page reads in ways nobody outside Amazon can separate from purchases.
Frequently asked questions
How many books does a BSR of 10,000 sell?
Nobody outside Amazon can tell you, and any tool that gives you a specific number is supplying a constant that has never been published. What can be said is relative: a book at BSR 10,000 sells roughly six to thirteen times as many copies a day as a book at BSR 100,000. This calculator reports that ratio and deliberately stops there.
Is Amazon Best Sellers Rank the same as sales?
No. Amazon describes rank as a book's customer activity relative to other books. It is a position in a queue, so a book's rank can fall on a day when it sold exactly as many copies as the day before, simply because the books around it sold more — and it can rise on a slow day if everything nearby slowed down further.
How often does Amazon update Best Sellers Rank?
Amazon says rankings are updated at least once per day, though changes can take up to two days to appear. Rank reflects both recent and historical activity, with recent activity weighted more heavily, so a single strong day does not immediately produce its full effect.
Why do BSR calculators disagree with each other?
Because each one privately chooses the constant that converts a rank into copies, and Amazon has never published it. The shape of the rank-to-sales curve is documented in academic research; the scale is not. Two tools using different constants will report figures 50% or more apart for an identical rank.
Does Kindle Unlimited affect Best Sellers Rank?
Borrows and page reads appear to influence Kindle rank, but Amazon has never confirmed exactly how, and no calculator can separate them from paid purchases. If a book is enrolled in Kindle Unlimited, treat any rank-based comparison of paid sales as unusable.
Can I compare a paperback rank with a Kindle rank?
No. Amazon maintains separate, independent ranks for each format, and category ranks are calculated differently again. Each is a distinct pool with its own size and sales density, so reading across them produces a meaningless comparison.