one-line definition
Session Duration is a core operating metric that helps small teams make better product and growth decisions.
formula: Measured as the time between the first and last interaction event in a single session.
tl;dr
Session duration is how long a user spends in your product per visit. Longer isn't always better -- it depends on your product. A quick-task tool should have short, frequent sessions. A content platform should have long ones.
Simple definition
Session Duration is the time between a user's first and last interaction in a single visit. Analytics tools like Google Analytics, Plausible, or PostHog measure this by tracking events (clicks, page views, scrolls) and computing the gap between the first and last event in a session.
Context matters. If you run a dashboard tool, a 45-second session where someone checks their numbers and leaves is a success. If you run an online course platform, a 45-second session means the user bounced before engaging. Don't optimize for longer sessions unless longer sessions actually correlate with retention or revenue in your product.
How to calculate it
Session duration = Timestamp of last interaction - Timestamp of first interaction in a single session
For aggregate reporting:
Average session duration = Total time of all sessions / Number of sessions
Say you had 400 sessions last week with a total combined duration of 8,000 minutes:
Average session duration = 8,000 / 400 = 20 minutes
Look at the distribution, not just the average. If 50% of sessions are under 1 minute (likely bounces) and 50% are 40+ minutes, your average of 20 minutes describes nobody. Segment by user type or entry page.
Example
You run a writing tool. Average session duration is 12 minutes. You segment by user status: new users average 4 minutes, returning users average 22 minutes. New users are leaving before they've written anything meaningful. You add a template picker to the first screen so new users can start with a pre-filled document instead of a blank page. New user session duration jumps to 11 minutes. You then check whether those longer sessions correlate with week-1 retention -- they do, at 2x the rate. Session duration was the leading indicator; retention was the outcome you cared about.
Related reading
Related terms
- MRR
- CAC
- LTV
FAQ
Why does Session Duration matter?+
It gives a fast signal about whether your product and distribution system is improving or regressing.