Formula
Users who reach activation event / Total new signups x 100
How to measure
Define the specific in-product event that counts as activation, then track the share of a signup cohort that reaches it within, for example, 7 days.
Why track it
Activation rate is the earliest reliable predictor of retention, and it is entirely within the product team's control to improve through onboarding design.
Example
Out of 1,000 signups in a week, 320 create a first project within 3 days, giving a 32% activation rate.