Measurement

System Usability Scale

The System Usability Scale is a standardized questionnaire used to measure perceived usability after people use a system.

Concept facts

The System Usability Scale is a standardized questionnaire used to measure perceived usability after people use a system.

Also known as
SUS, usability scale, perceived usability questionnaire.
Used in
Usability testing, product benchmarking, post-test evaluation, system comparison, release assessment, and UX reporting.
Interpret with
Post-task rating, usability benchmarking, task success, user satisfaction, success criteria, and test plan.

Plain-language explanation

The System Usability Scale, or SUS, is a short standardized questionnaire. Participants complete it after using a system, and the responses are converted into an overall usability score.

SUS is useful because it provides a compact measure that can be compared across studies or product versions. It is often used after participants complete several tasks with a system.

However, SUS does not identify specific usability problems by itself. It should be interpreted together with task performance, observation, errors, and participant comments.

Why it matters

Organizations often need a simple way to summarize perceived usability. SUS can help communicate whether users experienced a system as easy or difficult to use.

For institutions, SUS can support comparison across releases, platforms, or user groups. For example, a procurement dashboard, patient records system, or learning platform can be measured before and after redesign.

But the score must not replace issue analysis. A system may receive a moderate SUS score while still containing severe issues in high-risk tasks.

Use contexts

SUS is used when:

  • evaluating a product or system after use
  • comparing perceived usability across versions
  • adding a standardized measure to usability testing
  • reporting usability to non-UX stakeholders
  • tracking perception over time
  • complementing behavioral metrics

Application guidance

Use SUS after participants have had enough interaction with the system to form a judgment. Do not use it before users attempt meaningful tasks.

Interpret the score carefully. Pair it with task success, errors, time, confidence, and qualitative findings.

If comparing across groups or releases, keep the study conditions as consistent as possible.

Practical example

A corporate team tests a redesigned procurement approval portal with department managers, finance reviewers, and procurement officers.

After completing approval, rejection, document review, and vendor verification tasks, participants complete SUS. The score gives leadership a simple perceived-usability indicator, while the session findings explain the actual problems: unclear approval states, duplicate document checks, and weak exception handling.

Interpretive boundaries

SUS measures perceived usability, not task accuracy, accessibility compliance, policy correctness, or operational readiness.

It should not be used as the only measure of UX quality, especially in regulated or high-consequence systems.

Applied at Userhub

Userhub may use SUS when a standardized post-test usability measure is useful for comparing systems, releases, or user groups.

It is usually combined with task performance, issue analysis, user confidence, and qualitative evidence.

See Userhub UX Lab for applied UX research and evaluation context.

Sources and references

Bangor, A., Kortum, P., & Miller, J. (2008). An empirical evaluation of the System Usability Scale. International Journal of Human-Computer Interaction, 24(6), 574–594. https://doi.org/10.1080/10447310802205776

Brooke, J. (1996). SUS: A quick and dirty usability scale. In P. W. Jordan, B. Thomas, B. A. Weerdmeester, & I. L. McClelland (Eds.), Usability Evaluation in Industry (pp. 189–194). Taylor & Francis.

Lewis, J. R., & Sauro, J. (2009). The factor structure of the System Usability Scale. In M. Kurosu (Ed.), Human Centered Design (pp. 94–103). Springer. https://doi.org/10.1007/978-3-642-02806-9_12

Tullis, T., & Albert, B. (2013). Measuring the User Experience: Collecting, Analyzing, and Presenting Usability Metrics (2nd ed.). Morgan Kaufmann.

Cite this entry

APA

Userhub. (2026). System Usability Scale. UX Reference. https://userhub.com.bd/reference/system-usability-scale/