CPA (cost per action)
Also known as: Cost per action, Cost per acquisition
In short
Advertising cost divided by the number of recorded actions chosen as conversions, using a consistent outcome definition and reporting scope.
Specify the action before comparing costs
CPA is meaningful only when the action is defined. A form submission, qualified lead and purchase are different outcomes. Some teams use CPA to mean cost per acquisition, so clarify whether acquisition means a new customer or another counted conversion.
For a period, calculate observed CPA as ad cost ÷ counted actions. Keep the campaign scope, currency, counting rules and attribution basis consistent. Allow for conversion delays before comparing recent periods with mature data.
Google Ads Target CPA is a bidding strategy that seeks a desired average cost per conversion. It is not a promise that every action costs that amount, and the metric itself does not specify how media is billed.
Illustrative calculation
Imagine a fictional campaign spending $600 and recording 30 completed quote requests for the same reporting scope. Its CPA for submitted requests is $600 ÷ 30 = $20.
If only 12 requests later qualify, cost per qualified lead is a separate measure. Do not rename the first result as customer acquisition cost.
Check value and data quality
A lower CPA is not automatically better when the action changes or low-quality submissions increase. Review duplicates and downstream outcomes. Profitability also depends on the value and costs associated with those outcomes, rather than the reported advertising CPA alone.