Series Read-Through Calculator
Enter sales for each book in your series to see how many readers carry on from one book to the next, and how much each new reader of book 1 earns you over the whole series.
How read-through is calculated
read-through to book N = sales of book N ÷ sales of book N−1reader value = Σ (sales of book N ÷ sales of book 1) × royalty of book NRead-through from the previous book shows where readers drop off. Read-through from book 1 shows what share of book 1 buyers reach each book. Multiply each of those shares by the book's royalty and add them up, and you get what one book 1 buyer is worth on average, including book 1 itself.
Worked example: a strong series
A four-book ebook series prices book 1 at $0.99 ($0.35 royalty at 35%) and the rest at $4.99 ($3.28 at 70%, 2 MB files). Over 90 days it sold 800, 400, 320, 280 copies.
| Book | Sales | From previous | From book 1 |
|---|---|---|---|
| 1 | 800 | – | 100% |
| 2 | 400 | 50% | 50% |
| 3 | 320 | 80% | 40% |
| 4 | 280 | 88% | 35% |
Each book 1 buyer is worth $4.45, even though book 1 earns only $0.35. Spending up to that much in ads to sell one copy of book 1 still breaks even.
Worked example: weak read-through
With the same prices but sales of 800, 160, 96, 72, only 20% of readers go on to book 2. Each book 1 buyer is now worth $1.69. The later books keep readers well (60% and 75%), so the problem is book 1: its ending, its back matter, or readers who bought it for the price and were never the right audience.
Improving read-through
Fix the biggest drop first, which is almost always book 1 to book 2. Put a direct link to book 2 on the last page of book 1, with its cover and a one-line hook, before the acknowledgements and other back matter. Many readers stop reading at "The End", so anything after it is easy to miss.
Check that book 2 is easy to find and buy: the series page on Amazon should list the books in order, and book 2's description should say it continues the story. If book 1 is discounted or free, expect lower read-through, because some buyers pick it up for the price alone. Use the reader value with the break-even calculator to decide how much production cost each new series can carry.
Frequently asked questions
What is a good read-through rate?
There is no official benchmark, and it varies widely by genre and by how well each book ends. As a rough guide, many authors treat book 1 to book 2 as the hardest step, with later books keeping a much higher share of readers. Track your own numbers over time; the trend after a new cover or blurb on book 1 tells you more than any industry figure.
Should I use sales from the same month?
Use the same longer period for every book, such as the last 90 days, and leave out any book that came out during that time. Readers take weeks to move from one book to the next, so a single month undercounts later books and a new release overcounts them.
How do I count Kindle Unlimited readers?
Convert page reads to full reads: KENP pages read for a book divided by its KENPC (shown on your Bookshelf). Add those to the sales for each book, or run the calculator twice, once for sales and once for KU reads, since the two groups often behave differently.
What does the reader value tell me?
It is what one person who buys book 1 earns you across the whole series, on average. That is the most you can spend to get one book 1 buyer and still break even, which is the number to compare against your ad cost per sale from the ACoS calculator.
Sources
Rates last checked against KDP's help pages on 2026-10-16.
Guides that use this calculator
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