How does Amazon calculate Best Seller Rank?

Amazon's Best Seller Ranking (BSR) is calculated based on the product's sales, and is updated hourly, although Amazon won't specify exactly to what period of time the ranking applies. It also has nothing to do with product reviews or customer rating. A product with a rank of #1 means it has recently sold more than any other product in that category, on that store. If a product ranks #1 in BSR, that means it sells better than all the other products in that particular category and therefore gets the highest ranking than the other products.  However, since Amazon's BSR calculation also contains predictive capabilities, it can, on some occasions, rank a product higher, for its selling potential. It should be noted that BSR rankings are different for each Amazon marketplace, so, for example, a product could rank #57 in Amazon UK and #102 in Amazon US.  It should also be said that a high BSR ranking does not necessarily affect your overall sales.  It would be more beneficial to focus on optimizing the product description, look out for shipping to perform satisfactorily, and of course make sure to handle customer reviews and queries as efficiently as possible.