The percentage of measured website visitors or sessions that completed a desired business action (such as requesting a quote).
Conversion rate is the proportion of a defined audience or activity set that completes a specified action. State the action and denominator explicitly. A session-based rate and a user-based rate answer different questions and should not share an unlabeled percentage.
For a session-based completion rate, divide sessions containing at least one qualifying action by eligible sessions. For a user-based rate, divide users completing the action by eligible users under the same identity and period rules. Multiply by 100; if the denominator is zero, the rate is undefined. Counting every repeated event in the numerator produces a different measure.
The action also needs a defensible definition. A click to call is not necessarily a connected conversation, and a submitted form is not automatically a qualified opportunity. An improved rate can reflect audience changes or measurement changes as well as a better customer journey.
Takeaway: Use conversion rate to evaluate a clearly defined outcome. Keep lead quality, revenue and margin separate rather than assuming a higher percentage guarantees proportional revenue growth.
Example
A site records a successful inquiry in 20 of 500 eligible sessions. Its session completion rate is 4%. If some sessions contain repeated submissions, counting every submission instead would not measure the percentage of sessions that converted.
What to check
Show raw counts, scope and dates with the percentage. Check collection changes and compare similar audiences. In GA4, identify the relevant key-event rate and distinguish it from any linked advertising conversion measure.
For more detail, see About key events.