Engagement Rate is the percentage of sessions that qualify as engaged sessions. A common calculation is: Engaged sessions ÷ total sessions in GA4, or engagements ÷ reach/impressions on social platforms.
It matters because analytics turns marketing activity into decisions. Without clear measurement language, teams may misread performance, overvalue the wrong channels, or miss the actions that actually drive revenue.
Example
If 120 of 200 GA4 sessions meet the engagement criteria, engagement rate is 60%. Keep the stream’s timer and event definitions consistent when comparing periods, and do not substitute a social-platform engagement formula into the same report.