Formula
Users completing the action / Total users exposed x 100
How to measure
Define the specific action, like signing up or purchasing, then divide completions by the total audience that saw the opportunity to convert.
Why track it
Conversion rate is the universal unit for diagnosing funnel efficiency at any single step, from landing page to checkout.
Example
A landing page converting 400 out of 8,000 visitors into signups reports a 5% conversion rate.