CPA

CPA is the amount spent to generate one conversion — a sale, signup, lead or whatever action a campaign is optimized for.

CPA is close to CAC but narrower in practice: CPA is usually a campaign-level or channel-level number tied to a specific optimization event (a purchase, a lead form, an app install), while CAC is typically the company-wide blended number finance cares about. On ad platforms, "Cost Per Result" is the same idea wearing the platform's own label.

The word "acquisition" is doing a lot of work here — it doesn't have to mean a paying customer. A lead-gen campaign's CPA might be cost per form fill, which is a much cheaper and much less meaningful number than cost per paying customer. Always check which event the CPA is measured against before comparing CPAs across campaigns.