CPA (Cost Per Acquisition)

CPA (cost per acquisition) is the average advertising cost to generate one conversion, a sale, signup, or other target action. It is calculated as CPA = total spend ÷ conversions. If you spend $1,000 and get 50 sales, your CPA is $20.

The term is used two ways. As a metric, CPA measures how efficiently a campaign turns budget into outcomes. As a pricing model, a CPA deal means the advertiser pays only when a defined action completes, shifting delivery risk onto the network or affiliate. "Acquisition" is sometimes read as "action," which is why CPA and cost-per-action are used interchangeably.

Why it matters#

CPA is the metric closest to profit, because it counts the thing you actually want, not intermediate signals. It connects upstream costs to downstream value: your CPA is roughly your CPC (Cost Per Click) divided by your Conversion Rate (CVR), so a cheaper click or a better-converting funnel both lower it. A campaign is profitable when CPA sits comfortably below the value of each customer.

To know whether a CPA is good, compare it to revenue. ROAS (Return on Ad Spend) frames the same economics as a ratio of revenue to spend rather than a cost per action. When the conversion is a lead rather than a purchase, the same idea is measured as CPL (Cost Per Lead). Accurate CPA depends on clean conversion tracking, so attribution setup matters as much as the bid.

Related terms: CPC (Cost Per Click), CPL (Cost Per Lead), ROAS (Return on Ad Spend), and Conversion Rate (CVR).