SUS is a post-test questionnaire which means it administered at the end of a usability session. They reflect on how users perceive the usability of the application as a whole.

SUS score above 68 is considered above average and anything below 68 is below average.

Covers USABILITY CRITERIA.

This metric do not tell us why users struggle with a design, nor do they provide direct insights as to how we can improve it. They simply are a way of keeping track of how the users feel about the experience of using a product or service.

Pros

• Have a free normed database of scores.
• The biggest advantage to using the SUS is that it's such an old scale that there is a large amount of industry-wide data available to help benchmark your score and understand it in the context of your peers and competitors
• SUS correlates strongly with a much simpler metric, the single-question Net Promoter Score;
• SUS is considered a technology-agnostic questionnaire, meaning the items aren't specific to any technology or platform.

Cons

• Complex scoring method promising to mistakes because a 0–100 score is not equivalent to a percentage score;
  • To score the SUS, follow these steps:
    1. For odd items, subtract 1 from the user response.
    2. For even-numbered items, subtract the user responses from 5. This scales all values from 0 to 4 (with 4 being the most positive response).
    3. Add up the converted responses for each user and multiply that total by 2.5. This converts the range of possible values from 0 to 100 instead of from 0 to 40.
    4. Average together the scores for all participants
• User impressions of the experience as a whole are subject to the peak-end effect (that is, the most intense and last parts of the experience, either positive or negative, impact participants' recollections and evaluations the most);
• it doesn't address usefulness or utility.

t consists of 10 items that users rate from Strongly Disagree (1) to Strongly Agree (5).

1. I think that I would like to use this system frequently.
2. I found the system unnecessarily complex.
3. I thought the system 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 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.