System Usability Scale (SUS) Plus

Enhansed System Usability Scale (SUS) tool

Original System Usability Scale (SUS) was developed by John Brooke in 1986, it allows you to evaluate a wide variety of products and services, including hardware, software, mobile devices and websites. It is a is a simple, ten-item Likert scale with five response options for respondents; from Strongly agree to Strongly disagree. It provides a "quick and dirty", reliable tool for measuring the usability.

SUS is particularly relevant when you want to compare two versions of an application that are based around different technologies. It allows you to make that comparison, at least as far as perceived usability goes. Because SUS is pretty much technology-neutral, you can continue to use it as technology evolves over the years, and you don’t have to continually reinvent questionnaires.

Why "Plus" in the name?

usabiliTEST's version of the tool is called SUS Plus, because it affers two additional options:
  • Adjective Rating Scale
  • Promoter Rating Scale

Adjective Rating Scale was added in order to help answer the question: "What is the absolute usability associated with any individual SUS score?". It is an optional eleventh question to the SUS. However, instead of following the SUS format, a seven-point, adjective-anchored Likert scale was used to determine if a word or phrase could be associated with a small range of SUS scores.

Promoter Rating Scale is based on Net Promoter Score (NPS), a management tool that can be used to gauge the loyalty of a firm's customer relationships, developed by (and a registered trademark of) Fred Reichheld, Bain & Company, and Satmetrix Systems. The score is calculated based on responses to a single question: How likely is it that you would recommend our company/product/service to a friend or colleague?


SUS was developed as part of the usability engineering programme in integrated office systems development at Digital Equipment Co Ltd., Reading, United Kingdom.
  • Brooke, J B (1996). SUS - a quick and dirty usability scale. In: ‘Usability Evaluation in Industry’, Jordan, P, Thomas, B, Weerdmeester, B, and McLelland, I (eds). Taylor and Francis: London.

  • Brooke, J B (2013). SUS – a retrospective. Journal of Usability Studies, Vol. 8, Issue 2, February 2013 pp. 29-40.
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