ACOS
Measure efficiency
Ad spend divided by attributed book sales.
Free tool · No signup required
Amazon Ads ACOS calculator, built for KDP royalties.
Calculate break-even ACOS, a profitable CPC ceiling, and profit per advertised sale from what your book actually earns, not from its list price alone.
Book economics
Build your profitable bid ceiling
Book format
24-828
Calculated royalty per sale
$5.35
After $2.44 printing
Advertising assumptions
Orders / clicks
Your goal
Your break-even advertising numbers
Know the line before you raise a bid
30% target is below break-even
Break-even ACOS
41.2%
Target 30%Break-even 41.2%
- Royalty per sale
- $5.35
- Max profitable CPC
- $0.53
- Profit at 30% ACOS
- $1.45
- Target CPC
- $0.38
At 10% conversion, about 10 clicks produce one sale. You can pay up to $0.53 per click to break even, or $0.38 to hold your target ACOS.
Amazon.com estimate. Kindle Unlimited, organic sales, and series read-through are not included.
Bid planning
Break-even bid by conversion rate
Only the conversion assumption changes. Maximum bids are rounded down because a bid ceiling should never be rounded above break-even.
| Conversion rate | Clicks per sale | Max bid (break-even) | Bid at target 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 |
Optional campaign check
Where your campaign actually sits
Copy five figures from the same Amazon Ads date range. Nothing connects to your account or leaves your browser.
USD
USD
Optional
Enter spend, ad-attributed sales, clicks, and orders to compare your actual campaign with this book's royalty.
The important distinction
Amazon measures sales. You keep a royalty.
ACOS compares ad spend with the full list-price revenue attributed to ads. Profitability depends on the smaller amount left after Amazon's share, printing, or Kindle delivery.
Margin
Find break-even
Royalty divided by list price reveals the limit.
CPC
Set a bid ceiling
Royalty multiplied by conversion rate sets max CPC.
Worked example: a 120-page black-ink paperback at $12.99
Royalty per sale
$12.99 × 60% − $2.44
$5.35
Break-even ACOS
$5.35 ÷ $12.99
41.2%
Max CPC at 10%
$5.35 × 10%
$0.53
Profit at 30% ACOS
$5.35 − $3.90
$1.45
How to use the result
Treat the bid as a ceiling, not a promise.
Conversion rate is the least certain input and can differ by keyword, placement, format, and season. Use the table to see how quickly a safe bid changes when that assumption moves.
Wait for a useful sample before changing bids. Check search terms and placement data alongside ACOS rather than reacting to one click or one sale.
Configure the book
Choose paperback, hardcover, or Kindle and enter the production details used to estimate its Amazon.com royalty.
Set advertising assumptions
Enter the expected conversion rate and the ACOS target you want the campaign to hold.
Review the guardrails
Compare target ACOS with break-even ACOS, then use the maximum CPC and target CPC as bid ceilings.
Check a live campaign
Optionally enter spend, clicks, orders, and impressions from one report date range to estimate actual campaign profit.
Decision guide
Read ACOS in context.
There is no universal good ACOS. Your margin, campaign goal, data volume, and the value of later sales all change the decision.
Below target
The campaign leaves more profit than planned. Consider careful scaling if conversion and inventory are stable.
Between target and break-even
The attributed sale is still profitable, but the campaign gives up more margin than your target allows.
Above break-even
The attributed unit sale loses money. That can be intentional for launch or rank, but it should be a conscious budget choice.
ACOS, TACoS, and report data
Use each measure for the decision it can support.
| Measure | Formula or source | Use | Key distinction |
|---|---|---|---|
| ACOS | Ad spend ÷ ad-attributed sales | Campaign efficiency | Uses only sales attributed to ads. |
| TACoS | Ad spend ÷ total sales | Whole-book advertising context | Includes ad-attributed and organic sales. |
| This calculator | Your assumptions and estimated KDP royalty | Planning bids and break-even limits | Does not read an advertising account. |
| Amazon Ads report | Recorded spend, clicks, orders, and attributed sales | Reviewing actual campaign results | Source for final report and attribution-window data. |
Need to inspect the underlying margin?
Open the full KDP royalty breakdown.
Compare price points, production costs, minimum prices, and royalty options before funding ads.
FAQ
Questions, answered.
What is ACOS, and what does Amazon measure it against?
ACOS, or advertising cost of sale, is ad spend divided by the sales attributed to those ads, expressed as a percentage. Amazon measures those sales at the book's list price, not at the royalty the author receives.
How do I calculate break-even ACOS for a KDP book?
Divide the royalty per sale by the list price and multiply by 100. A $5.35 royalty on a $12.99 paperback gives a 41.2% break-even ACOS. Spending more than that share of attributed sales loses money on the advertised sale.
Why is break-even ACOS lower than the royalty rate?
KDP applies the print royalty rate to the list price and then deducts printing cost. A paperback on the 60% tier therefore keeps less than 60% of its list price. Kindle delivery charges can similarly reduce the effective margin on the 70% option.
What is the maximum CPC I should bid?
At break-even, maximum CPC is royalty per sale multiplied by conversion rate. If a book earns $5.35 and 10% of clicks become orders, the break-even CPC is $0.53. The calculator rounds bid ceilings down rather than above break-even.
What is a good ACOS for a KDP book?
A profit-focused ACOS should be below that specific book's break-even ACOS. A higher ACOS can be intentional during a launch or ranking campaign, but it means accepting less profit or a direct loss on attributed sales.
Is ACOS the same as TACoS?
No. ACOS divides ad spend by ad-attributed sales. TACoS divides ad spend by total sales, including organic sales, and gives broader context on how advertising affects the whole book business.
Does this include Kindle Unlimited page reads or series read-through?
No. Kindle Unlimited page reads, organic sales influenced by advertising, and revenue from later books in a series are not attributed reliably to one ad click. Treat this result as the defensible economics of one attributed unit sale.
Can this calculator replace Amazon Ads reports?
No. Use it for planning and quick campaign checks. Amazon Ads reports remain the source for final spend, clicks, orders, attributed sales, and attribution-window data.
Are these Amazon's official numbers?
The KDP printing-cost and royalty inputs are transcribed from Amazon's public US help pages. ACOS, CPC, and profit are arithmetic derived from those estimates and the assumptions you enter. Nothing is read from your advertising account.
After the numbers make sense
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Tool updated September 22, 2026
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