Much like CPA, eCPA is measuring the effective cost per action, or effective cost per acquisition. The use of a effective CPA allows an advertiser to measure the what it cost you to reach that goal, and standardize this measurement regardless of the pricing model you use to purchase the media. The eCPA formula is written as
eCPA = Total cost of an ad / Total number of actions taken
Once again, as a publisher, you might be more inclined to measure based on revenue generated, but the approach is still the same.
eCPA = Total earning from an ad / Total number of actions taken