The System Usability Scale (SUS)
The System Usability Scale is a ten-item questionnaire created by John Brooke in 1986 to give a quick, reliable measure of perceived usability. Participants rate each statement from strongly disagree to strongly agree, and the answers convert to a score from 0 to 100.
The core ideas
The main points of The System Usability Scale (SUS):
- Ten statements alternating between positive and negative wording
- Five-point agreement scale for each statement
- Odd items: subtract 1 from the answer; even items: subtract the answer from 5
- Add the ten results and multiply by 2.5 for a score out of 100
- Published research puts the average score at about 68
How to apply it to your product
Give the questionnaire right after participants complete realistic tasks, before any discussion. Compare scores between versions of the same product rather than treating one score as absolute.
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Common mistakes
- Reading a SUS score as a percentage
- Changing the wording of the statements, which breaks comparability
Preguntas frecuentes
What is a good SUS score?
Scores above roughly 68 are above average. The score is not a percentage, so compare it with benchmarks or earlier versions of your product.