Using session-based metrics like Average Session Duration per Session and Average Session Duration per User, we were able to measure website or app activity in the previous version of Universal Analytics (UA). But since Google Analytics 4 (GA4) was released, the emphasis has been on user engagement, which offers additional details on how consumers actively interact with your website or mobile application.
Average Engagement Time per Session:
This is the average length of time people spend using your app or website in a productive manner in a single session. Rather than just counting the amount of time a user spends passively on a page, GA4 measures user activity (clicks, swipes, and interactions) to quantify engagement time.
Calculation: It is calculated by dividing the total engagement time by the total number of sessions.
Average Engagement Time per Session=Total Engagement Time / Total Number of Sessions
Use Case: You may use this measure to see how long users spend actively interacting with your content in a given session.
Average Engagement Time per User:
Definition: The average amount of time a user spends actively using your website during each session is measured by this metric.
Calculation: It is calculated by dividing the total engagement time by the total number of users.
Average Engagement Time per User=Total Engagement Time / Total Number of Users​
Use Case: This metric tells you how long a user spends on your site on average over the course of several sessions.
How to Locate These GA4 Metrics:
In order to view these stats within your GA4 property:
Go to Engagement >> Overview or Events report in GA4 contains the average engagement time each session.
You can either manually calculate Average Engagement Time per User by dividing Total Engagement Time by the Total Users, or you can construct a custom exploration in GA4's Explore section.