System Usability Scale (SUS) Plus


What is SUS and how it can help you improve usability of your product?

Logo for usabiliTEST System Usability Scale Plus (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 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. And while the SUS is often referred to as an “industry standard” in the business and technology industries Brooke himself has noted “it has never been through any formal standardization process”.

Below are the ten items on the scale:

  1. I think that I would like to use this system frequently.
  2. I found the system unnecessarily complex.
  3. I thought the system was easy to use.
  4. I think that I would need the support of a technical person to be able to use this system.
  5. I found the various functions in this system were well integrated.
  6. I thought there was too much inconsistency in this system.
  7. I would imagine that most people would learn to use this system very quickly.
  8. I found the system very cumbersome to use.
  9. I felt very confident using the system.
  10. I needed to learn a lot of things before I could get going with this system.

SUS is particularly relevant to user experience 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 in usability testing 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 offers two additional options:

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?

In addition, our online version of the tool includes built-in system usability scale calculator. The data is analyzed in real time and calculates the following values:

It is important to note that raw SUS scores are not expressed as percentages and must be normalizes to produce a percentile ranking. Also, SUS scores can be translated into letter grades, which may be helpful for communicating results to stakeholders. Our tool takes care of both of these tasks as well, producing instant and easy to read values.

Acknowledgments

SUS was developed as part of the usability engineering program 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.
  • Bangor, A., Miller, J. & Kortum, P. (2009). Determining what individual SUS scores mean: Adding an adjective rating scale. Journal of Usability Studies, 4(3), 114–123. Retrieved from

Blog article

What Is the System Usability Scale (SUS) and Why Is It Important?

The system usability scale (SUS) is a great way to evaluate the usability of your product. Learn more about the system usability scale here.


To launch your SUS+ test today, create an account here. It only takes a few minutes to set up this test. In the end, you'll save hours on data analysis; you will also gain valuable insight from the brilliance of your participants' minds.