Task Success Rate & Time-on-Task

When users use a digital product, a central question arises: **Are they achieving their goals - and how efficiently are they doing so? Two of the most meaningful quantitative metrics in UX research answer precisely this question: the Task Success Rate and the Time-on-Task. Both metrics are robust, comparable and together form an objective basis for evaluating the usability of applications.

How Successful are Users? - The Task Success Rate

The so-called task resolution rate indicates how many people were able to complete a certain task completely and correctly. It is given as a percentage and is particularly suitable for measuring the effectiveness of a system.

Practical example: In a usability test, users were asked to open an account in a banking app. Out of ten test subjects, seven successfully get to the last step. Three aborted beforehand - partly because the “Next” button was difficult to see and partly because the input fields were unclear. Result: Task Success Rate = 70 %. A clear indication of optimization potential in the onboarding process.

Variants of the Survey

• Binary: Success yes/no - easy to survey, but not very differentiated.
• Ratings: Additionally distinguish between “complete”, “partial” and “aborted” - particularly useful for complex tasks.
• Error-based: Additionally analyze why tasks fail - e.g. technical errors, misunderstandings, usability problems.

The success rate is also very suitable for comparisons between versions, e.g. for redesigns or A/B tests. The metric can also show whether improvements actually have an effect over longer periods of time.

How Efficient is the Use? - Time-on-task

While the success rate describes the achievement of a goal, the Time-on-Task records the effort required to achieve it - usually in the form of the time needed.

Practical example: In an e-commerce test, the order process on the old version of a checkout page took an average of 3:20 minutes. After a UI redesign, the processing time drops to 1:50 minutes. The average Time-on-Task is reduced by 45% - a clear indication of greater efficiency.

But: Less time is not automatically better. An extremely short time-on-task can also indicate superficial processing or lack of interest. Therefore, this metric should always be interpreted in the context of the task and user goals.

How is it Measured?

• For moderated tests: by stopwatch or digital timer
• For digital systems: automatically via log files, session recording or analytics
• Important: Start and end points must be clearly defined (e.g. first click on “Log in” to last entry)

Strong Together: Effectiveness & Efficiency

The two metrics only become fully meaningful when combined. A task can be completed quickly - but still fail frequently. Or it is usually completed successfully, but takes a remarkably long time.

Example combination: In an intranet test, 90% of users manage to find a specific piece of information - but it takes them over 4 minutes on average. The interpretation: The system works, but not efficiently. A better navigation or search function could help here.

Best Practices from the Field

• Formulate tasks realistically: The task should correspond to the real context of use.
• Operationalize start and end points: This is the only way to consistently record times and success rates.
• Do not simply delete outliers: A user needs 10 minutes because the interface is blocked in a certain constellation - this is not a “measurement error”, but a valuable insight.
• Triangulating with qualitative methods: Statements from interviews or thinking aloud help to interpret figures (“Why was the task difficult?”).

Conclusion

Task Success Rate and Time-on-Task are proven tools for making user performance measurable. As quantitative metrics, they provide clear, comparable and meaningful data about the usability of a system - provided they are used context-sensitively and methodically clean. In practice, they are indispensable for benchmarking, redesign evaluations and continuous UX optimization.

Last modified: 17 June 2025