Cost-per-Active-User (CPAU) is a metric that measures the financial effort a company needs to invest to generate active users.
Generally, an active user is a person which is identifiable (by an ID, e-mail or username) by a company. Furthermore, the active user is interacting with the corresponding business during a specific period. Every company has to define what activity specifically means in this context. Oftentimes, this largely depends on the offered service or product (e.g. a messaging service will define activity different to an e-mail provider).
Usually, active users are reported as:
- Daily Active Users (DAU) – typical for businesses where users expectantly interact on a daily basis (e-mail, calendar, games)
- Weekly Active Users (WAU) – typical for businesses with weekly frequency (forums, social communities, mobile apps)
- Monthly Active Users (MAU) – typical for many B2B apps where users presumably interact few times a month or less (e-mail providers, accounting & bookkeeping)
Keep in mind that users who interact daily will as well appear in the weekly and monthly reports.
Companies can easily calculate their CPAU by taking the invested budget and simply divide it by the number of users generated through the corresponding campaign.