SUMMARY
Purpose: Task Completion Rate is a quantitative usability metric that measures how effectively users complete a designed task, helping teams understand real-world usability bottlenecks.
Design Thinking Phase: Test
Time: 45–60 min session + 1–2 hours analysis
Difficulty: ⭐⭐
When to use:Validating a design pre-launch with real usersTesting a new user flow for task efficiencyComparing two design variations using benchmark metrics
What it is
Task Completion Rate is a quantitative usability metric used in UX testing to measure the percentage of users who successfully complete a given task. It's a foundational way to evaluate whether a digital product is easy to use and whether key interactions are intuitive.
📺 Video by NNgroup. Embedded for educational reference.
Why it matters
Task Completion Rate gives designers and product teams a clear signal about real usability. While qualitative insights explore the "why" behind behaviours, Task Completion Rate reveals “if” users were able to complete essential tasks—and how consistently. It’s often a go-to metric for comparing iterations, tracking UX improvements over time, and aligning stakeholders around measurable outcomes.
When to use
- In usability tests during the prototyping or validation phase
- When refining complex user flows like onboarding or checkout
- To quantitatively benchmark a redesigned product or journey
Benefits
- Rich Insights: Helps uncover user needs that aren’t visible in metrics.
- Flexibility: Works across various project types and timelines.
- User Empathy: Deepens understanding of behaviours and motivations.
How to use it
- Choose specific tasks representative of real user goals (e.g., “Transfer funds,” “Book an appointment”).
- Test with a minimum of 5–10 users matching your personas.
- Clearly define success criteria for each task (e.g., “User reaches confirmation page without assistance”).
- Run moderated or unmoderated sessions using usability platforms or live tests.
- For each task, mark whether the user succeeded, gave up, or needed help.
- Calculate the Task Completion Rate:
Task Completion Rate (%) = (Number of users who completed the task / Total users) × 100 - Analyse drop-off patterns and clusters of failure to guide design improvements.
Example Output
During a usability test of the mobile check-in process for a fictional healthcare app, 10 users attempted the same 3-step check-in task:
- Task: Check in for an upcoming appointment via the app
- Success Criteria: Reaches final screen confirming completion
Results:
- 8 out of 10 completed successfully without help
- 1 needed assistance at the document upload step
- 1 gave up at the second screen due to unclear interaction
Task Completion Rate: 80%
Common Pitfalls
- Vague task definitions: Results are unreliable if users don’t understand what’s expected.
- Confusing success criteria: Be explicit—is success reaching a page, performing an action, or avoiding errors?
- Small or biased samples: Avoid overinterpreting results with too few participants or unrepresentative users.
- Overreliance on numbers: Always pair quantitative metrics with observed behaviours.
10 Design-Ready AI Prompts for Task Completion Rate – UX/UI Edition
How These Prompts Work (C.S.I.R. Framework)
Each of the templates below follows the C.S.I.R. method — a proven structure for writing clear, effective prompts that get better results from ChatGPT, Claude, Copilot, or any other LLM.
C.S.I.R. stands for:
- Context: Who you are and the UX situation you're working in
- Specific Info: Key design inputs, tasks, or constraints the AI should consider
- Intent: What you want the AI to help you achieve
- Response Format: The structure or format you want the AI to return (e.g. checklist, table, journey map)
Level up your career with smarter AI prompts.
- Get templates used by UX leaders — no guesswork, just results.
- Design faster, research smarter, and ship with confidence.
- First one’s free. Unlock all 10 by becoming a member.
Prompt Template 1: “Analyse Drop-Off Points in a User Flow”
Analyse Drop-Off Points in a User Flow
Context: You are a UX researcher reviewing usability test data for a [check-in process] in a [healthcare app].
Specific Info: The Task Completion Rate is [73%], with completion failures at the [document upload] step. User personas include [older adults aged 60–75].
Intent: Identify UX issues leading to task failure, and suggest what should be tested next.
Response Format: Provide a summary of likely friction points, severity level, possible root causes, and 1 top design fix to test.
Ask clarifying questions if steps or personas are unclear.
Suggest one follow-up research activity.
