Task Load Index
What is Task Load Index (TLX)?
Task Load Index (TLX) is a subjective, multidimensional assessment tool used in user research to measure the perceived workload of completing a specific task. It evaluates six different factors: mental demand, physical demand, temporal demand, performance, effort, and frustration level.
Synonyms: NASA-TLX, Workload Assessment, Cognitive Load Measurement, User Task Evaluation

How Task Load Index (TLX) is Used in User Research
Task Load Index (TLX) is a valuable tool in user research for assessing the cognitive and physical demands of various tasks. Researchers use TLX to:
- Evaluate interface designs
- Compare different versions of a product
- Identify areas of high workload in user interactions
- Optimize task allocation in complex systems
By understanding the perceived workload, designers can create more user-friendly and efficient interfaces.
Benefits of Using Task Load Index (TLX)
Implementing TLX in user research offers several advantages:
- Quantifiable results: TLX provides numerical scores that can be easily compared and analyzed.
- Multidimensional assessment: It considers various aspects of workload, giving a comprehensive view of user experience.
- Versatility: TLX can be applied to a wide range of tasks and industries.
- Validated methodology: As a well-established tool, TLX has been extensively tested and validated in numerous studies.
How to Conduct a Task Load Index (TLX) Assessment
To use TLX in your user research:
- Have participants complete the task you want to evaluate.
- Immediately after task completion, ask participants to rate each of the six factors on a scale (usually 0-100 or 0-20).
- Optionally, have participants weigh the importance of each factor.
- Calculate the overall workload score by combining the ratings and weights (if used).
- Analyze the results to identify areas of high workload or potential improvements.
Frequently Asked Questions
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What are the six factors measured in Task Load Index (TLX)? The six factors are mental demand, physical demand, temporal demand, performance, effort, and frustration level.
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Is Task Load Index (TLX) only used in software user research? No, TLX can be used in various fields, including aviation, healthcare, and manufacturing, to assess task workload.
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How long does it take to complete a Task Load Index (TLX) assessment? The assessment itself is relatively quick, usually taking 5-10 minutes to complete after the task is finished.
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Can Task Load Index (TLX) be used for remote user testing? Yes, TLX can be adapted for remote testing by using online forms or specialized user research tools.