What is Time on task?
Time on task measures how long a user takes to complete a specific task, serving as a core efficiency metric in usability evaluation.
How it works
Time on task is typically measured in usability studies using screen recording timestamps. Shorter times indicate more efficient designs, but context matters: a short time on a help article might indicate efficient scanning, or it might indicate that the user gave up quickly. Time on task is most meaningful when compared between design versions (A vs. B), between user groups (novice vs. expert), or against benchmarks. It often follows a lognormal distribution (most users are fast, a few are very slow), so geometric means or medians are more appropriate than arithmetic means. Outliers often represent users who got stuck, which is qualitatively important even if statistically excluded.
Applied example
After redesigning a checkout flow from 5 pages to 2 pages, median time on task drops from 4 minutes 30 seconds to 2 minutes 15 seconds. Importantly, the slowest 10% of users (who previously averaged 12 minutes) now average 4 minutes, indicating that the redesign especially helped struggling users.
Why it matters
Time on task quantifies the efficiency dimension of usability, complementing task success rate to provide a complete picture of whether users can accomplish their goals quickly and easily.
