The Sales Estimator turns an Amazon Best Seller Rank into an estimate of how many copies a book sells per day and per month. BSR is the clearest public signal of how a book is selling, but on its own the number means very little: rank 40,000 sounds close to rank 4,000 and is nothing like it.
The estimate is modelled, not measured. Amazon does not publish sales figures for individual books, so no tool can read them — this one applies a mathematical curve to the rank you enter and shows a range rather than a single number, because a rank observed once is a noisy sample.
Where it goes further than a rank-to-sales table is money. Give it a list price and a page count and it works out the royalty rate KDP actually pays at that price in that marketplace, subtracts the real printing cost, and shows what would reach you per copy rather than what buyers pay Amazon.
No. Amazon does not publish per-book sales figures to anyone outside the account that owns the book, so no third-party tool can show real numbers. This converts a public rank into an estimate using a mathematical model.
They are directional. The curve has not been calibrated against real KDP royalty reports, so treat the output as a way to compare books and size up a niche rather than as a forecast. The monthly range shown on the page is the honest expression of that uncertainty, and it widens deliberately as the rank gets weaker.
It depends entirely on the store and the category, which is why this page shows a generated reference table instead of quoting fixed numbers. Enter a rank to see what the model estimates for it, and compare it against ranks you already understand.