CPA (Cost-per-action) refers to the fee an advertiser pays each time a new lead takes a predefined action (i.e. buying an item) which can be attributed to a promotional campaign from an affiliate.

It measures how much money is spent on a particular marketing activity and its impact on sales. In other words, it’s an effective way to measure which advertising methods are most likely to encourage a user to take action.

CPA is calculated by dividing the total amount of money spent on a marketing campaign by the number of new customers acquired or leads that have been attracted as a result.

CPA = Marketing budget (per specified period of time) / new customers (in the same period of time).