Formula
Count of active free-tier or trial accounts
How to measure
Count distinct accounts that are active but not on a paid plan at the reporting date.
Why track it
The free user base is the top of the monetization funnel for a freemium model, and its size and engagement quality shape future paid conversion volume.
Example
A freemium product grows its free user base to 200,000 accounts while converting roughly 3% to paid each quarter.