Catalog
concept#Product#Analytics#Quality assurance#Software engineering

System Usability Scale (SUS)

A standardized ten-item questionnaire for rapidly measuring perceived usability of products. Produces a single numeric score for evaluating and comparing interfaces.

The System Usability Scale (SUS) is a standardized ten-item questionnaire for rapidly assessing perceived usability of interactive systems.
Established
Medium

Classification

  • Low
  • Business
  • Design
  • Intermediate

Technical context

Online survey tools (e.g., Qualtrics, LimeSurvey)User testing platforms for recruitmentAnalytics and reporting tools

Principles & goals

Standardization for comparabilityCombine with qualitative dataTransparent protocols and instructions
Discovery
Domain, Team

Use cases & scenarios

Compromises

  • Misinterpreting small sample sizes
  • Relying on SUS without complementary qualitative insights
  • Unstandardized execution distorts comparability
  • Combine SUS with qualitative follow-up questions
  • Provide standardized instructions to all participants
  • Segment by user profile for deeper interpretation

I/O & resources

  • Prototype or product version
  • Recruited test participants
  • Standardized tasks and instructions
  • SUS score and segmented analyses
  • Short report with recommendations
  • Data basis for release decisions

Description

The System Usability Scale (SUS) is a standardized ten-item questionnaire for rapidly assessing perceived usability of interactive systems. It yields a single numeric score to compare products and evaluate design changes in user research and product development. The method is lightweight, widely adopted, and supports quantitative comparisons across users and iterations.

✔

  • Fast, cost-efficient collection of usability indicators
  • Easy to implement and evaluate
  • Enables quantitative comparisons across versions and groups

✖

  • Measures perceived usability only, not actual behavior
  • Limited diagnostic depth for specific issues
  • May contain cultural or language biases

  • SUS overall score

    Scaled value (0–100) as primary measure of perceived usability.

  • Mean and distribution by segment

    Statistical measures to analyze group differences.

  • Delta between releases

    Difference in SUS score to evaluate design changes.

E-commerce checkout study

Comparison of checkout workflow before and after redesign using SUS to measure perceived usability and acceptance.

Mobile app iterative tests

Small, recurring SUS surveys during sprints to verify whether changes improve user perception.

Enterprise software evaluation

Summative measurement of usability of complex internal tools to prioritize UX investments.

1

Define goal and population, create test protocol

2

Recruit participants and conduct tasks

3

Conduct SUS survey, analyze and contextualize

⚠️ Technical debt & bottlenecks

  • Undocumented protocols hinder replication
  • Outdated questionnaire translations without validation
  • Automated surveys without quality controls
Participant recruitmentSample sizeContext variances
  • Comparing SUS scores from different task sets
  • Interpreting single items as full conclusions
  • Using without linguistic validation in other countries
  • Underestimating context when interpreting scores
  • Ignoring expectations and user experience
  • Missing triangulation with qualitative data
Basic UX research skillsBasic statistical skills for evaluationExperience with questionnaire design and instruction
Comparability across releasesMeasurability of UX changesSimplicity of data collection
  • • Results are context-dependent and not universally generalizable
  • • Requires standardized instructions for comparability
  • • Language adaptations must be validated