Cost Per Action (CPA) / Effective Cost Per Action (eCPA)

Also known as: cost per acquisition

A campaign pricing model in which an advertiser pays only when a user completes a defined conversion event — such as downloading a file or submitting a form registration. The formula is straightforward:

CPA = total cost of campaign ÷ number of conversions

CPA is an umbrella term that encompasses several action-specific variants depending on the campaign objective, including cost per download (CPD) and cost per install (CPI).

The primary advantage of CPA pricing is that spend is tied directly to results. Unlike impression-based models such as CPM (cost per mille), CPA eliminates exposure to false signals like fake views — advertisers are only billed when a genuine conversion occurs.

eCPA (effective cost per acquisition) is a related metric used for benchmarking and comparison. It calculates what the CPA would have been had the advertiser purchased conversions directly, even when the campaign was actually bought on an impressions or clicks basis. This allows cross-model performance comparisons within or across campaigns.