True ACOS
Ad spend divided by the royalties your ads actually earned. Break-even is 100 %, and that is the point.
What it measures
True ACOS = Ad spend ÷ Ad-generated royaltiesIn plain words: for every $1 of royalty my ads earned me, how much did I spend to get it?
- Under 100 % — the ads pay for themselves.
- Over 100 % — every ad-driven royalty costs more than it returns.
Why not plain ACOS
Amazon's ACOS divides ad spend by ad-attributed sales value — the price the customer paid. But you do not keep the customer's price, you keep a royalty. On a $4.99 ebook at 70 %, roughly $3.44 reaches you, and on a paperback far less.
ACOS therefore looks flattering on books where your royalty share is small. True ACOS uses the royalty, so break-even is exactly 100 % on every book, every format, every marketplace.
Some tools use "TACOS" for ad spend ÷ total sales. That measures how ad-dependent you are, not whether the ads are profitable. Both are useful; they answer different questions.
How ad-generated royalties are built
Two parts:
| Part | Source |
|---|---|
| Paid sales | Ad-attributed units × the book's real royalty per sale, taken from your KDP data |
| Kindle Unlimited | The KU royalties Amazon reports directly against your ads |
The paid part is an estimate, because Amazon never reports the author's royalty on a sale — only the retail value. TrueRoyalties uses the royalty per sale that book actually realised, rather than a generic 70 % rule.
Reading it well
- A high True ACOS on a book 1 can be fine if the series pays it back. Check Series and read-through before cutting the campaign.
- True ACOS ignores the organic lift your ads create, so it is a conservative measure.
- It needs Amazon Ads connected. Without it, the card is empty.
Where to find it
On the dashboard as a KPI card, per book on Books, and per marketplace on Marketplaces.