01
Plain definition
ACOS — advertising cost of sales — is the share of attributed sales you spent on ads: ad spend divided by the sales those ads produced, expressed as a percentage. An ACOS of 40% means forty cents of advertising for every dollar of sales the campaign is credited with.
02
Why it matters to an author
It is the number that tells you whether an ad campaign pays for itself. Because a sale only returns the royalty, not the list price, an ACOS can be well under 100% and still lose money — the break-even ACOS is roughly your royalty share of the price.
03
Where it appears in the publishing workflow
Advertising dashboards report it per campaign and per keyword. It belongs in the profit calculator as a variable acquisition cost per sale, next to platform and payment fees.
Continue