Break-even Calculator

Work out your break-even ACOS and maximum cost per click from your own royalty, Kindle Unlimited and series read-through figures.

What a click is worth to you

Break-even ACOS and your CPC ceiling, worked out from your own royalty, Kindle Unlimited and read-through figures.

Format and royalty tier

Print Ebook 70% Ebook 35%

Switching this changes every figure below. Kindle Unlimited borrows only exist on ebooks, so print has no KENP inputs at all.

Format and royalty tier

Your book

List price ($)The price showing on your book’s Amazon page right now.

Delivery fee ($)70% tier only. KDP shows this on the pricing screen when you set your ebook price. A text-only novel is usually a few cents.

Print cost ($)Shown on the KDP paperback pricing screen. It changes with page count, ink and marketplace, so use your own figure.

Kindle Unlimited

KENP page countYour KENPC, on the KDP Bookshelf under the book’s details. Usually a good deal higher than your printed page count.

Average read completionHow much of the book a typical Kindle Unlimited borrower gets through.

Your read completion (%)Pages read divided by (borrows × KENPC) over the same period, from your KDP reports.

KENP rate per page ($)

Share of readers who borrow rather than buy (%)From your KDP sales report: pages read divided by KENPC gives you roughly how many borrows you had, against paid units over the same weeks.

Your series

Books in the seriesHow many books a reader could go on to read after this one. Put 1 for a standalone.

Read-through between books (%)Of the readers who finish book one, the share who start book two. Divide book two’s units by book one’s over the same window. 60% is a placeholder. This input moves the result more than any other.

Your ads

Conversion rate — readers per click (%)

Target profit margin (%)How much of each reader’s value you want to keep. 0% bids right up to break-even.

Break-even ACOS — full series —

Your CPC ceiling —

Royalty per sale	—
Royalty per KU borrow	—
Blended revenue per reader	—
Series lifetime value per reader	—
Break-even ACOS — book 1 alone	—
Break-even CPC	—

Change one field at a time and watch which ones move the answer. With no ads running yet, skip conversion rate and read the ACOS figures instead.

Why ebooks and print give such different numbers

Print is the simpler case. Every sale is a sale Amazon counts, and break-even lands near 22%, roughly where the familiar 30% benchmark sits.

Switch the format to ebook and it climbs past 200%.

The difference is Kindle Unlimited. A borrow is not a sale. It pays you for pages read, and Amazon leaves that money out of the division that produces ACOS entirely. If half your readers borrow, half your income is invisible to the number you are judged on.

For a KU series, break-even above 100% is ordinary.

How to use the CPC ceiling

This is the most you can average per click and still hit your margin. Amazon asks you for a bid, which is a different thing.

What you actually pay per click is usually less than your bid. With dynamic bidding it can briefly be more, and placement modifiers move it again depending on where the ad shows.

So treat the ceiling as the line your average has to stay under. Start bids near it, then check your realised average CPC in the reports and adjust from there.

Read-through moves the answer more than anything else

Read-through is the share of readers who finish one book and start the next. It compounds: at 60%, book three reaches 36% of your book-one readers. At 40%, the series is worth about a third less.

Yours: units of book two divided by units of book one, over the same weeks. Rough, and still better than a number someone else picked.

60% is a placeholder. There is no industry average worth quoting, because it depends on how well book one ends and how easily a reader finds book two.

You can use this before you have any ad data

With one book published and nothing running, it still tells you your royalty per sale, what a borrow is worth, and what a reader is worth across everything you have written.

Come back with a few hundred clicks and a real read-through rate.