CPA, or Cost per Acquisition or Cost per Action, is a metric that is tracked in many direct response and performance campaigns, particularly in verticals that are tracking user conversions — whether that conversion represents a sale or a form submission, depending on what the advertiser decides. This is why it’s also often referred to as Cost per Conversion.
Some marketers will include “clicks” as a viable action — in those cases, the calculation is essentially equivalent to a CPC (Cost per Click).
A related concept is eCPA, or Effective Cost per Acquisition. This is often calculated by advertisers who pay on another cost basis such as CPM or CPC, but wish to convert it to a Cost per Acquisition in order to optimize their media buying to some Cost per Acquisition target.
It is calculated as follows:
( sum of the relevant media costs / total # of acquisitions )
So, if a display campaign spent $1,000, and garnered 20 conversions, then the the eCPA = $1000 / 20 = $50
