System Usability Scale

SUS

stempsychologysocial sciencesFree for research use

Permission: Free for research use. Free for non-commercial academic research, with no licence fee. Cite the original publication.

A 10-item questionnaire giving a global view of subjective usability. Alternates positively- and negatively-worded items. Produces a single 0–100 score; 68 is commonly cited as the average.

Items

Response format

5-point Likert scale

Version

1.0

Ready-to-cite methods sentence

Perceived usability was measured using the System Usability Scale (SUS; Brooke, 1996), a 10-item instrument scored on a 5-point Likert scale. Item scores were transformed per Brooke's formula and summed, yielding a composite 0–100 SUS score (a mean of 68 across 500 studies is a common benchmark; Sauro, 2011).

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Reliability & validation

Notes

α = .91 reported by Bangor, Kortum, & Miller (2008) across 2,324 surveys from 206 studies.

Validation population

Software users across many systems

Cronbach's α

0.91

Response anchors

Strongly disagree · Disagree · Neither agree nor disagree · Agree · Strongly agree

Known limitations

SUS produces a 0–100 score, not a percentage or percentile. Historically © Digital Equipment Corporation (1986); Brooke (1996) made it freely available, and the only condition is that published reports acknowledge the source. Substitute "system" with the product name when administering.

Original citation

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.

Questions researchers ask

What does the SUS measure?

A 10-item questionnaire giving a global view of subjective usability. Alternates positively- and negatively-worded items. Produces a single 0–100 score; 68 is commonly cited as the average.

How many items does the SUS have?

The System Usability Scale (SUS) has 10 items.

Is the SUS free to use?

The SUS is free to use for non-commercial academic research. You don't need to pay a license fee, but you should always cite the original publication.

Is the SUS reliable?

Validation studies report Cronbach's α of 0.91. See the reliability section for the population studied and full statistics.

Who developed the SUS, and how do I cite it?

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Library entry verified September 2026. Metadata is provided for reference; item wording is available inside Folio Surveyor, subject to each instrument's licensing.