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Kindle Unlimited Subscribers

How Do Kindle Unlimited Subscribers Behave (And How Does it Impact Authors)?

Kindle Unlimited Subscribers

Kindle Unlimited has revolutionized the eBook experience for both readers and authors. Last year we took a look at how Kindle Unlimited affects authors and publishers. This year we want to take a closer look at the habits of KU readers compared to non-KU readers, and what that means for authors whose titles are enrolled in KU. We surveyed almost 1,000 readers and analyzed the results to find out what the takeaways are for the author community.

1. How does Kindle Unlimited work for the subscriber?

To start with the basics: Kindle Unlimited is a subscription service that allows readers to read the books available as part of the Kindle Unlimited library for “free” (think Netflix for books). The service currently costs $9.99/ month, and there are over 1.4 million titles available to enjoy. Most of the books available are either classics or titles published through Amazon imprints and Kindle Direct Publishing. This means that if, as a reader, you most frequently read titles by popular, best-selling authors, you may not find the names you recognize available in the KU library. To date, none of the major publishers have opted to make their titles available through KU.

KU readers can read as many books as they want per month. The one limitation is that readers can only have 10 Kindle Unlimited books downloaded to their devices at a time. This means that readers can’t “hoard” books the way that they may normally feel inclined to. When a subscriber is in the Kindle Store, whether it’s in the Amazon app, the Kindle app, or the Amazon website, they can see clearly which titles are available as part of their subscription.

2. How many Kindle Unlimited Subscribers are there?

Amazon has never publicized the total number of subscribers in KU. However, we do have some information about the KU program, and we can use our available data to estimate the total number of KU subscribers. We recently wrote an article on Kindle Unlimited Royalties where we have data points for the KDP Global Fund and the KENP payout rate. When you divide the global fund by the payout by KENP payout, you get the total number of pages read in KU for a given month.

For this exercise let’s use the data from February 2017. The Fund was $16.8 million and the payout per KENP was about $0.005.

KDP Global Fund / KENP Payout = Total number of Pages read in the month on KU

16,800,000 / 0.005 = 3,360,000,000

That’s over 3 billion pages read! If we assume the average novel is 250 pages, we can back into the number of novels read: 3,360,000,000 divided by 250 gives you 12,440,000 average length novels read through KU subscriptions per month.

Based on our survey data, KU subscribers read about 5 books per month. We can use this data to estimate a subscriber count for KU.

Number of KU Novels Read / Number of Novels read by one Subscriber = Total Number of Subscribers

12,440,000 / 5 = 2,488,000 KU subscribers

2.5 million readers in KU is a lot of readers, and because our calculations are based on pages read it’s likely that the 2.5 Million number represents the active readers enrolled in KU. We would guess there are even more inactive users who are subscribed but are not reading. There are limitations with our data, and we’re making quite a few educated assumptions but we think it’s safe to assume that there at least 3 million readers in Amazon’s Kindle Unlimited.

3. How many books does a KU subscriber read?

When we asked KU readers how many titles they read per month, one thing became apparent very quickly: Kindle Unlimited is filled of avid readers. Over 71% of KU subscribers read 5 books per month or more. Compare that to non-KU readers, where only 57% of readers read 5 books per month or more. That makes sense since KU subscribers pay $9.99 per month for the service, there is an incentive to get your money’s worth. Also, people who read a lot of books will get the most value from KU as they were likely spending more than $9.99 per month purchasing books. 20% of our KU subscriber sample said they read more than 20 books per month!

 4. Do Kindle Unlimited Subscribers review titles, and when they do, do they count as verified?

When we asked our readers how often they reviewed the books they read, KU subscribers were more likely to leave a review than non-KU readers. 27% of KU subscribers review books somewhat often or very often, compared to Non-KU readers who review often or somewhat often only 20% of the time.

Reviews left by Kindle Unlimited subscribers do not show as verified reviews on Amazon. However, even if KU readers’ reviews don’t have the “verified” sticker on them, they still count toward your total review count and rank, so they are beneficial.

5. Do Kindle Unlimited Subscribers purchase books outside of the KU Library?

Yes! 77% of KU subscribers say that they still purchase books even if those books are not in KU. This means that if an author has a reader following in KU, then chooses to remove their books from KU, they are not alienating their KU readers. There is a high chance that those readers will continue to read and pay for their books.

6. What genres do Kindle Unlimited subscribers read?

We noticed that the genre popularity with KU readers mirrors the genre popularity amongst readers at large, with two notable exceptions.

First: Romance, Fantasy, and Mystery are the most popular genres for both KU and Non-KU readers. However, we noticed a heavier emphasis on Romance within the KU Readers, with 35% of KU readers citing Romance as their primary genre compared to 25% of Non-KU readers. This makes sense to us, as Romance readers are generally avid readers who consume multiple books per week, so KU makes sense for them. Romance authors who do not have a book enrolled in KU may want to consider it since over a third of KU readers enjoy Romance. Having a title available through KU is a targeted way to get in front of a group of readers who are predisposed to like Romance.

Second: We also noticed that Non-KU readers read more Mysteries, with about 17% of Non-KU readers citing Mystery as their primary genre compared to 10% of KU readers. We have a hunch that many Mystery readers feel loyalty to the best-selling authors (Patterson, Baldacci, etc.), whose titles are not available through KU, making Mystery readers less likely to subscribe.

7. Which type of Devices do Kindle Unlimited Subscribers read on?

Before we get into the differences between KU readers and Non-KU readers devices, let’s talk about the overall picture of reading preferences that came out of the survey. We were surprised to find that almost 75% of surveyed readers are reading on a phone or a tablet! This is important because modern phones and tablets all have a full internet browser and color screens. For authors, this is an extremely important finding for a few reasons.

  1. ‘Back matter’ or ‘front matter’ links will work very well on those devices because they have full browsers built in.

    That means adding a join the mailing list link in your book will allow the user to tap on it directly and join your list easily. With older Kindle devices, the ‘experimental browser’ is fairly limited and not reliable enough to collect emails well. The era of reader interactivity is upon us.

  2. It places additional weight on cover design.

    Now that the shopping experience will be mostly presented in color it’s even more important to have a professionally designed cover.

  3. It opens the door for certain image-heavy genres.

    This is really great for any genre that relies on imagery, for example: cookbooks, graphic novels, and children’s books. It may also allow for genres that were traditionally text-centric to make more use of color photos or audio snippets. Perhaps Fantasy authors with elaborate fictional worlds could offer pronunciation guides or colored maps. We’re excited to see how authors push the boundaries of multimedia now that the reading technology can support it.

Alright, but back to Kindle Unlimited. Do KU Readers have different device preferences? They do. KU readers are more likely to have a Kindle Branded tablet (Kindle Fire) vs. the Kindle app on a tablet or phone.

8. How many titles on the top charts are enrolled in Kindle Unlimited?

On the day that we checked (3/28/17), 60% of the best selling titles on the Amazon paid charts were enrolled in KU. With 88% of the romances, 76% of the fantasy, and 58% of the Mystery/Thriller titles being available through KU.

On the free charts, it’s a slightly different story. Only 41% of the top 100 books are in KU, with only 24% of romances, 14% of Fantasy, and 28% of mystery best selling free titles being enrolled. We believe that the difference between KU percentages on the free and paid charts are due to Amazon’s KDP rules. When your book is in KU, your ability to price the book at Free is limited to 5 days per quarter, which limits the an author’s ability to leverage free days as a marketing tactic.

% of the Top 100 Books that are in KU
% of the Top 100 Books that are in KU
All Genres 60%  41%
Romance 88%  24%
Fantasy 76%  14%
Mystery / Thriller 58% 28%

Since we pulled this data on a specific day these percentages are likely to jump around a bit, but this is a good snapshot for comparison.

9. What can Authors Expect?

There are a few main takeaways from all of the graphs above that we want to leave you with:

  • The KDP fund just keeps growing. Month over month the KDP fund gets bigger, which means that plenty of readers are actively reading the enrolled titles. If you can sell your book to this audience, then you’ll get a portion of that pot. The growth of KU means it’s here to stay, it’s no longer an experiment.
  • Romance authors benefit greatly from KU.  It’s hard to argue with the fact that 88 of the top 100 romance books on the bestseller charts were enrolled in KU. Romance readers are avid, and will gladly read through enough books in a month to make the $9.99 subscription fee worth it.
  • KU readers are incredibly active. KU readers read more books and review books at a higher rate. It’s safe to assume they are more active generally than their Non-KU counterparts.
  • You can use KU enrollment strategically. There is an opportunity to use KU enrollment as a strategy to acquire readers who then purchase your other books. If 77% of KU subscribers go on to purchase books outside of the program, then one reader acquisition strategy is to put some titles in KU, allowing those readers to read them for “free”, and then converting those readers into paying customers on your other titles.

Are your titles in KU? What has your experience been? We know that authors have to consider the pros and cons of KDP Select when deciding whether to enroll. Which side are you on?  Let us know your story in the comments!

A Note on Methodology

The following conclusions are based off of self-reported survey results from our author base. We did no heavy statistical analysis on the data, but rather took the raw data, cleaned it up, and made some logical inferences from what we saw. If you are a crazy market research pro, or a stats geek, please try not to hyperventilate.

*A previous version of this post claimed that KU readers’ reviews count as verified. That was incorrect. You can read Amazon’s official language around verified reviews here.*  

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52 comments on “How Do Kindle Unlimited Subscribers Behave (And How Does it Impact Authors)?
  1. Thanks for the info. All of my books are in KU, and my royalties for KU actually out-strip my regular sales. The big question is: How do we authors let readers know our books are available in KU?

    1. Personally, if I read one book by an author and like it, I follow them and get notifications of new releases. I very rarely buy kindle books but I am a heavy reader 5 + books per WEEK (not month as the graph shows). If you get on I’ll read everything you’ve got on KU (sometimes more than once if they’re good, not sure if that counts though).

  2. This is great insight. Thank you for carrying out this giant endeavor and sharing the valuable information.

    You have my heartfelt thanks.


  3. Hi Chloe, paid units vs. sold units are almost the same for my book on any given day. this information was interesting, and helpful.

    Thank you

  4. 8. How many titles on the top charts are enrolled in Kindle Unlimited?

    This category of your study is skewed. Amazon has two algorithms. One for KU that favors the titles in the program and ensures they rank higher.
    Another for out of program titles which is designed to bury those books and make them harder for the reader to find when searching.
    Reviews have more weight for KU titles and site visits that result in a download give the ku title more credit for ranking than a purchase of out of program books.
    The favoritism Amazon places on KU titles is endless.

    1. You are missing something 🙂 KU pays authors about a half a penny per page read, which works out to pretty much what that author would have made on a $2.99 retail sale of a 400 page book. Authors of shorter works make slightly less on KU, and authors of longer works make slightly more. However, the conversion rate for KU readers is much better than for non-KU because the incremental cost is 0. You are only asking for their time, not their money. KU is actually a best-case scenario for authors, with the only caveat that you aren’t allowed to sell your ebook on other stores.

      1. Marcia, my KU sales run from 30 to 50% of my income. I wouldn’t say we make nothing. I find that when I run a promotion on a book, my KU reads jump as well as my regular sales.

  5. Thanks for compiling & sharing this.

    I wonder if you can point to some evidence for #4 as far as Verified Purchase reviews. I’ve only ever heard it said that KU reviews are Unverified, and my own experience reflects this. I had a book which was perma-free for 3 months and then (re)entered KU. During the Permafree period, it averaged about 20 reviews a month, all or nearly all Verified. Since entering KU, the reviews barely trickle in in spite of about 1000 daily page reads, and some reviews are Unverified. Since being in KU bars the book from availability elsewhere, those Unverified reviews can’t be coming from readers who bought the book elsewhere; they almost have to come from KU readers. (Of course, those reviewers could have bought a Paperback and reviewed the wrong edition, but I don’t sell many paperbacks!)

    So in summary, to my knowledge KU reviews are not Verified, and I also don’t particularly think KU readers are more likely to review than others.

    Thanks again for the interesting & useful data.

    1. Hi P.K.,

      Thank you for your comment, and for bringing the KU reviews discrepancy to our attention. You are correct, they do not count as verified. We have updated the post to reflect this. When it comes to the likelihood of the average KU reader to leave a review: the data we report comes from polling our reader audience. We have a large audience made of different sorts of readers, but there is a chance that they are not illustrative of the “average” reader. Thank you for contributing to the conversation!

      1. Hey Chloe,

        I’m told that KDP Support claims that reviews by KU readers are counted as Verified. However, it seems pretty certain that they don’t get the Verified Purchase tag. That makes sense given that they are not “purchases” at all. That would mean they look unverified but count as Verified in the algorithm, which is the important thing.

        As with anything pertaining to KDP, they don’t necessarily reveal everything to us… 🙂

  6. Hi Chloe

    This is Willow Rose’s publisher.
    It’s a no-brainer for us. We tried both wide and KU. When we were wide (B&N, Apple, Kobo, etc.) we earned 75% on Amazon-sales and 25% on the rest.
    After we put all our books(45+) in KU, we earn 33% on Amazon-sales and 66% on KENP(pages read). And we even sell Mysteries/Thrillers, which is not the best genre according to your survey.

    Thank you for all the numbers!


    1. I am curious as to what happened to your overall sales at the switch… did your income decrease and your Amazon income dropped or did your sales rise from surges in the page-reads?

    1. Hi Alasdair, Thank you for bringing the KU reviews discrepancy to our attention. You are correct, they do not count as verified. We have updated the post to reflect this.

  7. Thank you, Chloe, for doing all the hard work, and sharing. It convinces me that I’m right to have my books in KU. Advertising books for sale with you invariably results in more pages read too. I think it outweighs the restrictions KDP impose,

  8. Hi Chloe. First, I’m pretty sure that reviews by KU readers are NOT considered verified purchase reviews. Second, I get almost no reviews from KU readers. I think I’ve had one in the past year. And third, my KU books average out at 560 pages per book. Your 250 pages seems very low! Interesting exercise, and very helpful to us struggling authors. Thank you. I hope the trad publishers stay away from this pot as long as possible. 🙂

    1. Hi JJ,

      Thank you for your feedback, and for bringing the KU reviews discrepancy to our attention. You are correct, they do not count as verified. We have updated the post to reflect this.

  9. Hi Chloe,

    I’ve seen speculation on other blogs that KU readers may favor higher-priced ebooks since they ‘get their money’s worth’ that much quicker. If it’s true, it would point toward a higher-price strategy. Do you have any data that supports or refutes that speculation?


    1. Hi Tom!

      We saw some of that speculation too. However, it would seem, considering that the average number of titles read per month by KU readers is high (close to 10), that these readers are attracted to the program primarily because they read a lot of books, not because they are trying to “get their money’s worth”. Personally, (so, this is not based on data) I would think that it’s kind of like Netflix. Does a Netflix subscriber make sure to watch a certain number of hours of programming every month in order to get their money’s worth? I wouldn’t think so. They subscribe because they are already going to spend their time that way. KU readers are likely the same way. They were attracted to the service because they already read a lot, and this was a good way for them to gain access to a lot of books and save some money.

  10. Compare the payout. At .005 per page read, a KU book of 250 pages, if read to the end, earns its author $1.25.

    At the average non-KU price of 3.99 for the same 250 page book, the author would earn $2.79. And she’d earn it whether they read to the end or not.

    Food for thought.

    1. I was thinking the same thing but if you get 3x the readers in KU then you are looking at $3.75 vs $2.79 for the same readership.

      I am still unsure of whether you would actually have more readers with KU but it makes me think.

  11. I disagree with your conclusion that KU readers will follow authors to their non-KU titles. At the very least, your data shows you’ll lose 27% of potential readers. You’re taking a narrow statistic and expanding it to the general case. Those 77% may be only buying certain trad published authors or genres. Nothing in your data shows how many non-KU books they buy or how often. As your data does show, certain genres do better in KU. If a reader subscribes for romances, but also regularly reads biographies, which do not do well in KU, the biography authors may choose to distribute their books widely, and the KU reader would have to buy rather than borrow those books.

    1. Hi BR,

      That’s a great point. We certainly aren’t advocating for authors to enroll in KU and then pull their titles out, relying on the 77% retention rate. But we found that statistic to be intriguing enough that we felt that mentioning the potential to use enrollment strategically in order to gain new readers was worthwhile.

      1. I thought this data point was interesting as well and it ended up being my main takeaway. It’s worth knowing that the 23% of KU users surveyed didn’t report buying / reading books outside of KU. If we could drill down on that, we might be able to assume a bit more. Obviously, the findings would relate differently to each novelist.

        KU is a tricky point for me because I think I generally make half of what I would using KU, but of course, I can’t really tell because maybe the KU users that read my book might not have taken a chance on it otherwise — meaning — they might not have paid for the book. Sometimes, I might make up in volume what I have lost in sales. I’m planning on running some experiments over the next year, but by the time I release my data, everything could change.

        1. I agree. I’ve had several readers thank me for being in KU because they can’t afford to buy as many books as they’d like to read. I’ve also had readers tell me they found me through KU and gave me a try. They have then bought titles that aren’t in KU. For those who can’t afford to buy books, I would rather they give me a lower royalty than have them steal my book off of a pirate site.

  12. Great info – thanks for compiling & sharing.

    One thing I’ve found helpful about KU is the ability to tell if people are liking the book enough to read the whole thing. I’m a new author with only 1 book, so if the number of lages read correspond to the length of my book, it’s a pretty good indicator that they liked it enough to read all the way through. Not as good as a review, but helpful info nonetheless.

  13. I had the opposite experience. I don’t break even on a book til I take it wide. So I’ll release in KU, but I get out after one run and go wide to make sales.

      1. Shayne, the smallest signup period is 90 days.

        I’ve heard the opposite from JMason’s experience, that if you pull out too soon you’re going to lose money on those readers who would continue to discover the books there.

        I put in my reissued backlist for 180 days, and did make as much money on page reads as I did on actual purchases. I’m going to try the program again with a new series, this time with Amazon and FB ads. We shall see.

  14. I didn’t read all the comments so someone may have touched on this. I look at KU this way. I reach readers who would probably never find or read my book without the program. Why? Because for an indie author to reach new readers, I think KU is the best possible way. Many months I make more from pages read than book sales. I’m sure others have had different experiences, but as a KU member, I will NEVER buy a book…unless at a used book store. Why should I when I have millions to choose from? With over 40,000 books published each month, my selection is endless. If I read the first chapter and don’t like it, then I’ve wasted no $$ and move to the next selection. In my book, pardon the pun, it’s a win-win for readers and authors. That’s just my two cents. I should probably get change. (and yes, I know books can be returned for a full refund, but I have to do that within 7 days of purchase. What if I have it longer than that before I begin to read it) With the growth of the KU program, I think authors are missing out if they don’t enroll their books. IMHO

    1. Ann,

      LOL, you and I are opposites! I’m a KU member to try new authors & genres and explore the market for my own writing.

      But I also buy ebooks voraciously. Don’t even want to see the total spent in 2017–thank God I can at least write them off.

  15. I’d be interested in more information on how to join KU. I recently published three books( Feb., Mar.2017) Record of Poems. All three are available in ebook, Two are color.Is this primarily a review site? I’m not sure I understand the mechanics of it except exposure for authors. The marketing strategies used today are so much different from they were when I started these books in the 80’s. I self published with Xlibris and my books are available now with Barnes and,, and Google search. I’m not sure if I am restricted to using only their purchasing methods or if Ku is a possibility. It is all very confusing to get the right marketing strategy and avoid the scams that plague the writing and publishing industries. I want to get my books seen by the right audiences and not break the bank doing it. Any suggestions or help would be much appreciated.

    1. Mark,

      Kindle Publishing has a plethora of information on their website.

      Also, there are numerous books out on starting out on Amazon. Just do some searches, and good luck.

  16. NO NO NO NO! I understand what you mean by “Romance Authors benefit greatly from KU.” They get their name out there yes, BUT many authors on KU make LESS than what they would originally make. The amount of money Amazon pays authors that are on KU has gone DOWN despite the activity going UP. Authors are NOT GETTING PAID FAIRLY. But, they remain on there to 1. Give readers that otherwise wouldn’t be able to afford them a chance to get into their works 2. Attract new readers that might not look at them otherwise and possibly because it comes with a free promotion every 90 days. It is financially great for the reader, TERRIBLE FOR THE AUTHOR and that’s likely why a lot of major publishers don’t make their books available on KU.

  17. All very interesting. As a non-fiction writer , my books are on the short side, mostly between 50 and 100 pages. When- KU was introduced I had a huge downturn in my royalties. Even if a KU member read my 100 page ebook in one sitting I make $0.50 for that read. With the exception of a few, the reason someone buys or downloads a non-fiction book is to find some targeted info on their interest. Rarely is non-fiction a page turner (can be with historical stuff and memoirs ) . While the fiction writers are doing about the same or even more w/KU, we non-fiction types are taking a financial bath, and yet I feel that our content is every bit as valuable as theirs may be entertaining.

    1. Everyone will have a different experience with this. If you can sell a short book for $2.99 easily, KU may not make much sense. If you have a book at $0.99 and it’s long enough to make $0.33 through KU if the whole thing gets read, it’s probably better not to opt out of the KU money.

      I think that for newer authors, KU is helpful because the reads help increase your sales rank. In my personal experience, I haven’t noticed much of a difference in income when my book drops off of its kindle unlimited cycle, but sometimes it does, especially for romance. It’s easy for a book to get lost after its initial launch if not initially enrolled in KU.

      Each person has to test their books and do many types of testing to see what works for them.

      1. Thanks Danny,

        Agree. I enroll all my books in KU to start with. Having just returned to my business, I have taken one book off of KU … but need to go wide it first to see what kind of results I will get. Then I’ll do the same with the other books, one by one.

  18. What are your thoughts on an author that puts just the first book of a series on KU to lure readers in then hope they like them enough to convert to paid readers for the rest of the non-KU series? My thought as a KU reader is Bait and Switch… underhanded. But I would like author perspectives on this.

    1. Mary Lee,

      Think of it this way – when you go to the grocery store to get some of those .33 cents a pound oranges you saw in the paper or online, you pat yourself on the back for getting a bargain. Are you angry at the store for having the rest of their produce full price? Probably not. The oranges are a ‘loss leader’, a way to get you in the door.

      I give away 1st books in my series free to newsletter subscribers. I want as many readers as possible to try the book and hope they’ll want to pay for the rest of the series.

      There are all sorts of techniques used to sell products. Unless this author is promising you a product she’s not delivering, it is not underhanded – it’s trying to make a living at what we love.

      Happy reading!

  19. Hi there and thank you…..

    This is a great read. I am a new author of a children’s picture book and my book is listed on Amazon with Kindle Unlimited and in paperback. I am trying to work out where I should target, advertise, blog to etc to catch these kindle unlimited users. Please can you suggest anywhere that I can post my book to get more visibility and people downloading on Amazon Unlimited?

  20. This is a really clever approach. Here’s an update:
    (1) In July 2020 the KDP Select Fund held $32 million — twice what it held at the time of your post. If the rest of your calculation holds, that’s about 5 million KU subscribers.

    (2) That’s still just a small fraction of all Kindle ebook readers. Less than 5 percent, I’d guess, since the Kindle app has been downloaded over 100 million times on Android alone.

    (3) Since only a small fraction of Kindle ebook readers are KU members, and some KU members wouldn’t buy a book if it weren’t in KU, I don’t see how authors sacrifice much revenue when they enter KDP Select. It seems like a nice promotion tool that adds potential readers without cannibalizing many other sales.

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