The Difference Between Completion Rate and Success Rate in UX
Completion and Success Rate are two important metrics used to measure user behavior. While these terms might sound similar, and many designers pursue them as the measurement of practically the same type of success, they capture very different aspects of the user journey.
✅ Completion Rate
Completion Rate measures the percentage of users who successfully complete a task in a flow or process. This metric is often tied to quantitative analytics and is typically used to evaluate broader funnels — such as e-commerce checkouts, form submissions, or any multi-step user interaction.
Example illustrated by NN Group
Imagine that 1,000 users start a multi-step checkout process on an e-commerce site, but only 300 of those users finalize the purchase by reaching the confirmation page. In this case, the completion rate would be 30% (300 completed tasks out of 1,000 initiated tasks).
Completion Rate helps identify drop-off points and friction in the flow, providing insights on where users get stuck or abandon the process altogether. It is essential for spotting bottlenecks and improving the flow’s usability. However, it doesn’t always capture whether users felt successful in completing their overall goal.
