Calculator
KDP read-through calculator
Book 1 ads often look unprofitable on their own. Add the rest of the series and Kindle Unlimited page reads to see what a new reader is actually worth, and what you can pay to get one.
- Free, no sign-up
An example three-book series. Replace it with your own numbers.
Your series
- Royalty per sale ($). What KDP pays you for one sale, after delivery or printing costs. KDP explains the sums for ebooks and paperbacks.
- Read-through (%). The share of book-1 readers who go on to buy or borrow each book, counted from book 1. Book 1 is always 100%.
- KENP pages read. Pages a Kindle Unlimited reader reads in each book. If they finish it, that is the book’s KENPC, shown on your Bookshelf under Promote and Advertise.
Book 1 ads
Kindle Unlimited (optional)
Series multiplier
One book-1 reader is worth $6.80 across the series, 2.00 times what book 1 earns on its own.
What a book-1 reader is worth
| Figure | Book 1 alone | With read-through |
|---|---|---|
| Value of one book-1 reader | $3.40 | $6.80 |
| Break-even ACoS on book 1 | 68.1% | 136.3% |
| Break-even CPC on book 1 | $0.34 | $0.68 |
A break-even ACoS over 100% is normal for a series. Book 1 can cost more in ads than it earns, because later books pay it back.
Per book
| Book | Reach | Value per reader | Adds per book-1 reader |
|---|---|---|---|
| Book 1 | 100% | $3.40 | $3.40 |
| Book 2 | 55% | $3.40 | $1.87 |
| Book 3 | 45% | $3.40 | $1.53 |
This assumes readers who find book 1 through your ads read on at the rates you entered, and that every Kindle Unlimited reader reads the pages you entered. The ACoS is the one Amazon shows you, on book 1 sales at list price, which leaves page reads out.
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Next step
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How the read-through calculator works
- 1Give each book in the series its value to one reader: its royalty to a buyer, or its page reads to a Kindle Unlimited reader.
- 2Weight each book by how many book-1 readers get that far. Say book 1 pays $3.40 a sale, 55% of readers buy book 2, then 45% reach book 3, each also paying $3.40.
- 3Add them up for the value of one new book-1 reader: $3.40 + $1.87 + $1.53, about $6.80.
- 4Compare it with book 1 alone. $6.80 is twice what book 1 earns on its own, so you can spend up to twice as much in ads to win a reader and still break even.
FAQ
How to work out your read-through
Read-through here is counted from book 1, as the share of book-1 readers who reach each later book. Take a few months of your KDP reports and divide each book’s sales by book 1’s for the same months. For Kindle Unlimited, divide each book’s pages read by its KENPC first to count readers.
Use a window long enough for readers to get through the series, and leave out months when a promotion pushed one book on its own. If you track read-through book to book instead, multiply as you go. 60% from book 1 to 2 and 75% from 2 to 3 is 45% from book 1 to book 3.
Where to find the KENP page rate
The calculator doesn’t fill in a page rate, because KDP sets a new one every month. It announces each month’s Kindle Unlimited fund near the 15th of the next month and shares it out by pages read. Divide last month’s KENP royalties by your pages read in your KDP reports to get the rate you were paid. KDP’s royalties estimator page explains how the rate is set.
Why your break-even ACoS can go over 100%
ACoS is ad spend divided by ad sales. On book 1 alone you break even when ACoS equals your royalty divided by the price. Once later books pay you back, book 1 can carry more ad spend than its own sales, so the break-even ACoS can pass 100%.
Kindle Unlimited pushes it higher still. Borrows don’t count as sales in your ad reports, so a series with many KU readers looks worse on ACoS than it really is. The calculator works out the ACoS you’d see in the ad console, so you can compare like with like.
Writing a single book? The breakeven ACoS calculator does the book-1-only version, and the CPC calculator turns a break-even ACoS into a bid. To find your conversion rate, try the conversion rate calculator.
New to advertising books? Start with our guide to Amazon ads for books.
Using read-through in your ads
The series multiplier is the same idea as the Order and KENP Impact Multipliers in Merch Jar’s Blended Metrics. You set them in your ad account settings, along with your profit margin. Merch Jar then combines each keyword’s ad sales, at your margin, with its KENP royalties and applies the multipliers, so every keyword shows a blended ACoS you can filter by or use in a rule. Ad Impact Multipliers explains the other things they can cover, like organic sales.