Amazon Ads ACOS Calculator for KDP Books
Break-even ACOS, maximum bid, and profit per sale — from your real KDP royalty, not a number you had to guess.
Your advertising assumptions
Your break-even advertising numbers
At 10% conversion you can pay up to $0.53 a click and still break even. At a 30.0% ACOS you keep $1.45 a book.
Estimates built from KDP's published royalty tables and the conversion rate you entered — not figures from your advertising account. Amazon reports ACOS against its own sales and attribution windows, so check your campaign reports before changing bids.
The royalty above comes from KDP's own published tables: printing costs (verified 22 July 2026) and royalty rates (verified 22 July 2026). The ACOS and CPC figures are arithmetic on that royalty — nothing here is read from your advertising account.
Break-even bid by conversion rate
Every row uses the same $5.35 royalty and the same 41.2% break-even ACOS — only the conversion rate changes. Bids are rounded down: a max bid is a ceiling, so rounding it up would put you above your own break-even.
| Conversion rate | Clicks per sale | Max bid (break-even) | Bid at 30% ACOS |
|---|---|---|---|
| 0.5% | 200 | $0.02 | $0.01 |
| 1% | 100 | $0.05 | $0.03 |
| 2% | 50 | $0.10 | $0.07 |
| 3% | 33.3 | $0.16 | $0.11 |
| 5% | 20 | $0.26 | $0.19 |
| 8% | 12.5 | $0.42 | $0.31 |
| 10%yours | 10 | $0.53 | $0.38 |
| 15% | 6.7 | $0.80 | $0.58 |
Where your campaign actually sits
Optional. Copy four figures out of your campaign report and this compares them against the same royalty above — no account connection, nothing leaves your browser.
Enter your spend, clicks and orders to see your actual ACOS.
Worked example — 6" × 9", 120 pages
Load this example ↑A 6" × 9" black-ink paperback at $12.99. Printing is $2.44, so you keep $5.35 — and the bid comes out of that royalty, not the list price. At 10% conversion the ceiling is $0.53 a click. Rates last checked 22 July 2026.
How the formula works
Amazon computes ACOS against the sales your ads produced. You are paid a royalty. The gap between those two numbers is the whole reason this page exists, and it starts with the royalty:
royalty per sale = (list price × royalty rate) − printing cost
That is the KDP Royalty Calculator's number — this tool runs the same code, so the two pages can never quote different economics for the same book. Everything else is a ratio of it:
break-even ACOS = royalty per sale ÷ list price max profitable CPC = royalty per sale × conversion rate ad spend per sale = target ACOS × list price profit per book = royalty per sale − ad spend per sale
Because printing cost comes out before the ratio, break-even ACOS lands far below the royalty rate: a paperback on KDP's 60% tier typically breaks even somewhere in the thirties. Bids round down, never up — a maximum CPC is a ceiling, and rounding a ceiling up puts you above your own break-even.
Every printing-cost and royalty constant behind this page is transcribed directly from KDP's public help pages, dated, and cited. They were last checked against KDP on 22 July 2026 — see KDP's printing-cost page and its paperback royalty page, and the results panel above for the pages behind your specific figures.
For the pricing side of the same question — where your list price should sit before you advertise it at all — read How to Price a Book on Amazon KDP.
Frequently asked questions
What is ACOS, and what does Amazon measure it against?
ACOS — advertising cost of sale — is your ad spend divided by the sales those ads produced, shown as a percentage. The important detail for a KDP author is what sits in the denominator: Amazon measures ACOS against the list price of the books sold, not against what you earned on them. Your income is royalty, so a 40% ACOS on a book that only pays 41% royalty is nearly breaking even, not a comfortable margin.
How do I calculate break-even ACOS?
Break-even ACOS is your royalty per sale divided by your list price. A $9.99 paperback that pays $3.69 royalty has a 36.9% break-even ACOS: spend more than 36.9 cents of every advertised dollar and the sale loses money. This calculator computes the royalty for you from KDP's own printing-cost and royalty tables, which is the step most ACOS calculators leave you to guess at.
Why is my break-even ACOS lower than my royalty rate?
Because printing cost comes out first. KDP's 60% paperback rate is applied to your list price, and then the printing cost is subtracted — so a $9.99 book on the 60% tier does not keep $5.99, it keeps $5.99 minus printing. That leaves a break-even ACOS well below 60%. For a Kindle eBook on the 70% plan the same thing happens with the delivery fee.
What's the maximum CPC I should bid?
At break-even, your maximum cost per click is your royalty per sale multiplied by your conversion rate. If a book earns $3.69 and 8% of clicks become orders, it takes about 12.5 clicks to make a sale, so 12.5 clicks may cost at most $3.69 — about $0.29 a click. The break-even bid table on this page shows how that ceiling moves as the conversion rate changes, since that is the assumption most authors are least certain about.
What's a good ACOS for a KDP book?
Below your own break-even, which is a different number for every book. The 25–30% rule of thumb repeated across advertising blogs comes from physical-product selling, where margins and price points are nothing like a print-on-demand paperback. Work out your break-even first, then decide how much of it you are willing to give up for rank, reviews, or read-through across a series.
Does this account for Kindle Unlimited page reads?
No. If your book is in KDP Select, page reads add income that this calculator does not estimate, which means your true break-even ACOS is higher than the figure shown here. The KENP Calculator for Kindle Unlimited Royalties does that half — it turns page reads into earnings using a dated per-page rate. The same goes for organic sales an ad campaign helps along and for series read-through. Those three together are what people mean by blended ACOS or TACoS, and estimating them means guessing at a halo nobody can attribute — so this page does not. Treat the number here as the floor you can defend with a single attributed sale, and the blended figure as headroom you have to earn evidence for.
Which royalty does it use for a Kindle eBook?
Whichever plan you select. The 35% plan has no delivery fee and works at any eligible price. The 70% plan pays more but only inside a marketplace-specific price band and subtracts a delivery fee based on your file size — a large file at a low price can push the royalty below zero, in which case no bid is profitable and this calculator says so instead of showing a percentage. Kindle figures here exclude VAT, which KDP subtracts before applying the rate in some marketplaces.
Why does it use the standard royalty and not Expanded Distribution?
Because Amazon Ads drives sales on Amazon, and those pay the standard 50%/60% tiered royalty. Expanded Distribution's flat 40% applies to bookstores, libraries, and other retailers, which your ads are not buying clicks for. Using an Expanded Distribution royalty in an ACOS figure would be budgeting against income the advertised sale never earns, so this tool deliberately doesn't offer the option.
Why does it sometimes refuse to show a number?
KDP doesn't publish every format in every marketplace — hardcover isn't offered in Japan, Canada, or Australia, for example — and rather than guess, the calculator names the reason. It also refuses when the royalty is zero or negative: a break-even ACOS of 0% is not an answer, it means the book loses money on every copy before a single click is bought, and the fix is a higher list price rather than a lower bid.
Are these Amazon's official numbers?
The printing-cost and royalty constants are transcribed from KDP's public help pages and dated — the results panel names each page and the date it was last checked, and links them. The ACOS and CPC figures are ordinary arithmetic on top of that royalty. Nothing here is read from your advertising account, and no figure is a prediction of how a campaign will perform.
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