There is no magic number to become an Amazon bestseller, but it is a lower threshold than most people would think if all of the sales happen at once or in a very short period of time. The number varies based on the category and sales volume at the time. For example, in some niche categories, a book may only need to sell a few dozen copies in a short period of time to become the top seller.

Amazon updates its bestseller lists hourly, so sales momentum over a short period will impact bestseller status. Having all of your preorder sales count at the moment of publication is a key way to drive your book up their lists. It is understood that Amazon tracks IP addresses and customer's payment information, so they can tell if someone is attempting to game the system.