CPA
CPA is the platform-level price of one conversion, the number the machines optimize and buyers negotiate with.
What CPA is
CPA, cost per acquisition or action, is what one conversion costs in ad spend: the campaign’s outlay divided by the purchases, signups, or leads it produced, the platform-level price of the outcome you asked its bidding to chase.
Why CPA matters
It’s the number the machines optimize and the buyers negotiate with: target-CPA bidding hands the auction a price per outcome and lets the algorithm hunt, and campaign health gets read as CPA against the margin each conversion carries. It’s also the most gameable number in the account, because what counts as the “action” and who gets credit for it are both settings.
Using CPA without being fooled
- Define the action strictly: purchases, not add-to-carts dressed up
- Mind the attribution window: platform CPA flatters inside generous credit rules
- Set targets from margin: the CPA a sale can afford, not last month’s average
- Split new versus returning: blended CPA hides expensive acquisition behind cheap repeats
Frequently asked questions
CPA vs CAC: what’s the difference?
Scope and honesty: CPA is a campaign’s platform-reported cost per conversion under its own attribution; CAC is the business’s all-in cost per genuinely new customer across everything. CPA steers campaigns day to day; CAC judges whether the steering worked.
Why does lowering target CPA sometimes kill volume?
The auction obeys literally: a stricter target tells the algorithm to bid only where cheap conversions look likely, and delivery shrinks to fit. CPA targets trade volume for efficiency on a curve; picking the point is the strategy, not a settings tweak.