CPA

CPA, or cost per acquisition (also cost per action), is the advertising cost of each conversion, such as a sale, sign-up or app install, used both as a performance metric and as a pricing model.

As a metric, CPA is simple: total spend divided by the number of conversions. As a pricing model, it moves risk to the seller, who is paid only when the agreed action happens. Affiliate programmes and card-linked offers work this way.

Most platforms now treat CPA as a goal for automated bidding rather than as a price. In Google Ads, Target CPA is an automated bid strategy. The advertiser sets the average cost per conversion it wants, and Google sets bids to win as many conversions as it can (Google Ads Help, accessed 9 November 2026). The advertiser still pays per click or per impression; the target is what the bidding system steers toward.

Two cautions apply. CPA depends on what counts as a conversion and on the attribution window, so two platforms can report different CPAs for the same sale. And CPA does not show whether the sale would have happened anyway. Incrementality tests answer that question.

Example: A subscription app pays a network $25 for each paid sign-up. In March the network delivers 1,200 sign-ups, so the app pays $30,000 at a fixed $25 CPA. A $30,000 CPM buy that drives 800 sign-ups works out at a CPA of $37.50.

Related terms: CPC, ROAS, incrementality, card-linked offer, attribution window.

Authoritative source: Google Ads Help, "About Target CPA bidding" (accessed 9 November 2026).