Break-even ACOS calculator
Amazon judges your ads against the price the customer paid. You get paid a royalty. Those are different numbers, and the gap between them is why profitable-looking campaigns lose money. Here's the ACOS you actually need.
What the customer pays.
Ebooks at 70% also pay a small delivery fee.
Your KDP royalty report calls this "Avg. Manufacturing Cost".
Roughly $0.15 per MB in the US. Leave as-is if unsure.
How this is worked out
Break-even ACOS is simply your royalty divided by your list price. If you earn $3.43 on a $4.99 ebook, break-even ACOS is about 69% — you can spend up to 69 cents in ads for every dollar of retail sales and still come out level.
The reason it catches people out is that the ads console reports "sales" as the retail value. So a colour paperback listed at $14.99 whose printing costs leave you $2.10 has a break-even ACOS of 14%, and a campaign showing a "great" 40% ACOS is quietly losing you money on every order.
Print books are the harshest, because printing cost comes out of your side, not Amazon's. Ebooks at 70% are the most forgiving. Same ad, same console, completely different reality.
What break-even looks like across formats
| Book | List price | You earn | Break-even ACOS | ROAS needed |
|---|---|---|---|---|
| Ebook, 70% royalty | $4.99 | $3.43 | 68.8% | 1.5× |
| Ebook, 35% royalty | $2.99 | $1.05 | 35.0% | 2.9× |
| Trade paperback, b/w | $14.99 | $4.14 | 27.6% | 3.6× |
| Picture book, colour print | $10.99 | $0.52 | 4.8% | 21.0× |
That last row isn't a typo. A full-colour children's paperback can cost more to print than the author's entire share, which means the ad has to return twenty-one times its cost just to break even. Some books simply cannot be advertised profitably, and knowing that before you spend is worth more than any bid strategy.
What this calculator ignores, and why it matters
- Kindle Unlimited page reads. If your book is in KU, borrows earn you money that never appears in the ads console at all. Your real break-even is more forgiving than the number above.
- Read-through. An ad on book one that sells books two through five is doing more work than its own ACOS suggests.
- Organic lift. Ads that improve your ranking generate sales the ad never gets credit for.
So treat this figure as the strict floor: the point where the advertised book pays for its own advertising, ignoring everything else it does for you. For a series in KU, aiming somewhat above break-even is normal and sensible.
See this against your actual campaigns
Knowing your break-even number is step one. Step two is finding which of your keywords are already past it. Drop your Amazon Ads report into the free check and it will flag every search term that looks profitable in the console but isn't once your royalty is the yardstick. It runs in your browser — nothing is uploaded.
Check your campaigns freeRelated reading
- Why your Amazon Ads ACOS is lying to you — the longer explanation, including why a 14× return can still lose money and why your reports never agree with each other.
- KENP royalty calculator — what your Kindle Unlimited page reads are worth, and why the console can't see them.