Value Metric
Successful Task Completion Rate
Task Completion Rate is the percentage of users who successfully finish a defined task.
What is Successful Task Completion Rate?
Successful Task Completion Rate — often just "task success" — is the most fundamental usability metric: of the users who attempt a defined task, what share complete it correctly. It is binary and unambiguous, which makes it easy to measure and hard to argue with, whether in a moderated usability study or in live product analytics.
Defining "success" precisely (the correct end state, not merely reaching the last screen) is what makes the metric trustworthy.
How to calculate it
Task Completion Rate = Successful Attempts ÷ Total Attempts × 100
- Successful Attempts
- Attempts that reached the correct end state
- Total Attempts
- All attempts at the task
Worked example
If 39 of 50 participants complete a task correctly, task success = 39 ÷ 50 × 100 = 78%.
What good looks like
- Average across studies~78%
Across many usability studies the average task completion rate is roughly 78%; anything well below that flags a task worth fixing.
Source: MeasuringU (Jeff Sauro)
Why it matters
If users cannot complete core tasks, nothing else about the experience matters. Task success is the clearest signal of whether your product actually works for people, and its binary nature makes it a reliable target for iteration and a credible number to show stakeholders. Low success rates point directly to the flows that need redesign.
How to improve Successful Task Completion Rate
Locate the failure points
Run task-based usability tests to see exactly where and why users fail, then redesign those steps.
Verify fixes raise success
Re-test after changes and, where traffic allows, confirm the improvement with a live A/B test.
Frequently asked questions
What is a good task completion rate?
Across usability studies the average is around 78%, so rates meaningfully below that indicate a task worth investigating. For critical, must-complete tasks you should aim much higher — closer to the high 90s — because failure directly blocks users from value.
How do you define task "success"?
Define success as reaching the correct end state, not just arriving at the final screen. Set clear, objective completion criteria before testing so results are consistent and not subject to interpretation.