What a bestseller chart rank really tells you

By Daniel Rahl Jackson · Updated 20 October 2026

A chart rank answers one narrow question: how did this book sell in this store, compared with every other book, over a short recent period? It doesn't tell you how many copies were sold, and it can move a long way on surprisingly small numbers.

Store charts

Store charts such as Apple Books' top 100 are calculated by the store from its own recent sales and are refreshed at least daily. Apple publishes these charts for each country as public feeds, and they are the basis of BookTrendSpy. Two things make them useful. They cover dozens of countries in the same format, so you can compare markets directly. And they are separate for paid and free books, so a free promotion doesn't push paying titles off the list.

What they don't give you is volume. Apple doesn't say how many copies the number one book sold, and the gap between number one and number fifty varies from day to day and from country to country. A rank of #20 in Ireland and #20 in the United States represent very different numbers of readers. That is why the World Book Index counts how widely a book charts rather than pretending to know its sales.

Amazon's Best Sellers Rank

Amazon gives every book a Best Sellers Rank, updated roughly hourly and weighted heavily towards recent sales. Many authors convert it into estimated sales with calculators, but those conversions are approximations built from authors' reports, not figures from Amazon. Amazon doesn't offer its charts as open data, so they aren't part of BookTrendSpy.

Newspaper bestseller lists

Lists like those of the New York Times or USA Today are compiled weekly from reports by a selection of retailers, and editors decide which categories exist and how ebooks, bulk sales and series are treated. They are a measure of prestige as much as of sales, and their methods are not fully public.

How to read a BookTrendSpy page

• Countries today is the number of national charts a book is on today. Above five or six usually means a genuine international hit.
• Peak is the best position we have recorded, with the country and date.
• Days on charts counts days with at least one chart entry anywhere. Long runs matter more than a single high day: a book that sits at #40 for three months is usually selling more over time than one that touched #5 for a weekend.
• Wikipedia interest shows attention outside the shops. Spikes often come from adaptations, prizes, news or an author's death, and can arrive before the store charts move.

Common traps

Price promotions move ranks fast, especially for ebooks priced at $0.99 or $1.99 for a few days. Pre-orders can put a book on the chart before release. And translations are usually separate products with their own IDs, so a book's international reach is clearest on its author page, which brings the editions together.