System Usability Scale
The System Usability Scale (SUS) is a standardized questionnaire used to measure users' perceived usability of a software product or system.
“A simple, ten-item attitude scale giving a global view of subjective assessments of usability.”
(Definition reproduced from the ISTQB Glossary. Copyright belongs to ISTQB.)
View the complete ISTQB GlossaryWhat is System Usability Scale?
SUS consists of ten questions that produce a usability score, enabling teams to compare products and track usability improvements over time.
Standard questionnaire: Uses ten predefined statements.
Quantitative scoring: Produces a usability score from user responses.
Benchmarking: Supports comparison across systems.
Real World Example
A government benefits portal is adding an online application form used by people with different devices, abilities, and assistive technologies.
The feature can pass functional tests while still blocking users who rely on keyboard navigation, screen readers, captions, or sufficient color contrast. System usability scale keeps that risk visible.
The tester checks the application path with assistive technology expectations in mind, including labels, focus order, error messages, and completion without a mouse.
The team releases a service that more citizens can actually use because System usability scale is treated as a product quality concern, not a cosmetic review.
Practice Questions
Question 1
Which statement BEST describes System usability scale in the context of ISTQB terminology?
Question 2
A tester needs to explain System usability scale to a non‑technical stakeholder. Which approach is MOST appropriate?
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