Amazon | From the blog of Nicholas C. Rossis, author of science fiction, the Pearseus epic fantasy series and children's books


When I launched Honest Fibs the other day, I was pleasantly surprised to find out that with just a couple of dozen sales in a few days, it had reached the phenomenal sales rank of some #40,000.

This got me thinking: how is that even possible? I don’t think any of my older works have performed so well, even when they sell bigger numbers – say during a promo.

Then I came across a great resource, courtesy of The Passive Guy: an educated guess as to how Amazon’s ranking algorithm works, by John Doppler of Self-Publishing Advice. I examine his points here and look at how you can use them to increase your own sales.

Amazon’s Sales Rank

As a closely guarded secret, Amazon’s sales rank remains a perpetual source of confusion and myth. Authors find themselves asking questions like this all the time:

  • “Why did my sales rank go down when I sold more books this week?”
  • “Why did my sales rank go up when I didn’t sell anything?!”
  • “How did the sales rank of this book leapfrog over mine when I’ve sold ten times as many books?”

For example, why did Honest Fibs hit #40,215 in its first week of launch, after only a couple of dozen sales?

Sales Rank | From the blog of Nicholas C. Rossis, author of science fiction, the Pearseus epic fantasy series and children's books

Amazon won’t disclose their proprietary algorithms, but thanks to some clever analysis by indie authors, that formula has been reverse engineered. And once you understand that formula, the quirks of sales rank make much more sense, and you can use them to your advantage.

The basics of Amazon’s sales rank algorithm are surprisingly simple:

  1. Each sale or download of a product counts as one point toward a hypothetical “rank score”.
  2. Depending on the day, the preceding day’s score decreases by half, and is added to today’s points.
  3. For each category on Amazon, books are ranked based on their current scores.

The Details

There are some caveats, though. For example, as author Carolyn McCray points out, #2 would have you think that a book selling copies worth 128 “points” on Day-1, then never sells another copy, would see the following ranking:

  • Day-1 128 points
  • Day-2 64 points
  • Day-3 32 points
  • Day-4 16 points
  • Day-5 8 points
  • Day-6 4 points
  • Day-7 2 points
  • Day-8 1 point

In fact, there are multiple drop-off points, the first being the 24-hour window. After 24 hours your sales numbers are cut in half, but this does not happen daily. As a matter of fact, you are stable for several key periods: a week, a month, 3 months, 6 months, 12 month and 18-months.

That is why most people price too high for too long after a promotion and then suddenly, after a month of steady sales, fall from the sky in flames.

The most severe of these drops is the 30 day one. If you don’t bolster sales and convince the algorithm that you can still sell, you will fall off a rankings and sales cliff after a month.

Other factors include the following:

Sales rank is relative to other books

A book does not exist in a vacuum. As your book rises in sales rank, it will displace other books. As other books rise through the ranks, your book may be pushed downwards.

This counterintuitive feature of the algorithm is responsible for more confusion than any other.

The more recent the sale, the more weight it has

Because the formula weights sales by recency, the effect of a sales spike quickly fades. The algorithm favors steady sales over a dramatic surge.

Consider the two books below (Figure 1). Book A experiences slow, constant growth for the first two weeks. Book B offers a promotion which results in an explosion of sales, but those sales quickly settle back to normal levels once the promotion ends.

Sales Rank | From the blog of Nicholas C. Rossis, author of science fiction, the Pearseus epic fantasy series and children's books


At the end of the second week, Book A holds a higher sales rank — and has better visibility — even though Book B sold over three times as many copies.

In the long run, steady, organic growth outperforms sudden bursts of activity.

That is why publishing success is a marathon, not a sprint, so authors should be focused on long-term success.

Enrollment in KDP Select/Kindle Unlimited does not confer any direct advantage to sales rank

Titles in KDP Select do not receive higher placement just for enrolling in the program. However, downloads of books through Kindle Unlimited and Kindle Online Lending Library are treated as sales, and they are credited immediately.

A download is immediately recorded as a sale in the sales rank algorithm, regardless of what percentage of the book is read.

High sales rank does not guarantee high placement in search results

Sales rank plays but a minor role in determining the order of Amazon search results. Other factors such as relevance, keywords, sales history, product listing quality, and available inventory may influence Amazon’s algorithms. Therefore, a book with high sales rank may appear later in search results than lower-ranked books.

It takes twice as many sales to hit a rank than it does to maintain it

Because each day’s sales rank builds on previous sales, twice as many sales are needed to initially achieve a rank as compared to maintaining that rank. In other words, an author may need 40 sales to initially hit a given rank, but once that momentum is established, they will only need 20 sales per day to maintain that score (sales rank may still fluctuate due to the performance of other titles around it.)

Similarly, if no sales are made, the book’s score is cut in half on the following day.

Twice as many sales are needed to hit a rank initially; each day without sales halves a book’s score.

Pre-orders are counted immediately

Pre-orders are counted on the day the book is ordered, rather than on the date of the book’s release. This explains how books that have not yet been released may have a high sales rank, a common source of confusion.

Sales momentum is a key factor in the algorithm. The early boost from pre-orders have the potential to propel a title onto the Amazon charts faster and for a longer period of time than a launch day blitz alone would.

In Summary

Let me repeat the algorithm’s key points:

  • Sales rank is relative, and changes in rank may be due to the performance of other books
  • Higher sales rank does not mean higher overalls sales
  • It takes half as many sales to sustain a rank as it does to initially hit it
  • A launch day blitz may briefly attain a high sales rank, but steady, organic growth will sustain it
  • Pre-orders increase visibility and jump-start your book’s sales rank
  • Kindle Unlimited downloads immediately affect your sales rank, regardless of whether they are read

Taming the Algorithm

Sales Rank | From the blog of Nicholas C. Rossis, author of science fiction, the Pearseus epic fantasy series and children's books

Image by © Royalty-Free/Corbis

What does all this mean for your marketing?

You need to be running some form of significant promotion monthly and rotate that around your library. Have each of your books on sale, countdown deal or giveaway each month. Advertise the promotion, to make the most of it. And be sure to have a big push for your “Flagship” titles once every six months, or they could die away.

Amazon ads, Google Adwords, and FB ads can also help keep a steady stream of sales to help build “traction” inside the algorithm.

Why is this important? Because the more “banked” sales you have, the more responsive your title is to a sales push. As author Carolyn McCray explains, flagship title will rise much more quickly through the rankings under the exact same sales push than a younger title with less historical sales to its credit. And the difference can be huge.  McCray mentions that her better-selling titles can rise as much as quadruple the rankings than a less selling one – with the same amount of units sold. The key factor is long-term sales and this “traction” you have inside the algorithm.

You can think of Amazon’s algorithm as an equation that is constantly downgrading your chances at getting into the alsobot queue – that list of books under each title page that reads, “Customers who bought this also bought…” This is the single largest sales source on Amazon, and you need to keep reminding the algorithm that you can sell enough books to keep those alsobot slots alive. So, run strategic promotions to both maximize your ROI and keep the algorithm happy.

But this also means that you need to write a lotYou need at minimum 12 books/collections out to really make a go of this, and even more is better so that you can constantly have marketing promotions in the mix.

Still, volume alone does not sell books. No one will talk about your book if they can’t find it. The vast majority of people on Amazon find their books through the alsobot and the bestselling lists. Both of which are predicated on you selling enough books to keep your name out there.

This doesn’t happen by magic. It happens by promotion. And promotion is only successful if you understand how the algorithm works!

You can check out some great comments on The Passive Guy and on Self-Publishing Advice.