Chapter 5 Likert Scales
Some significant applications are demonstrated in this chapter.
5.1 Example one: System Usability Scale (SUS)
5.1.1 Calculating the SUS Score
However, if you are wondering how SUS calculator works, here’s a quick overview. As mentioned above, SUS survey consists of 10 statements and each one is presented in a form of a Likert five point scale, ranging from 1 to 5. The odd numbered questions express positive attitudes, while the even ones - negative. In order to calculate SUS score you subtract 1 from the user responses to odd statements, and subtract corresponding values from 5 in the even-numbered statements. At this point the converted response scale will be ranging from 0 to 4 with four being the most positive. By adding responses from all participants and multiplying the total by 2.5 converts the range from 0-40 to 0-100.
https://www.usabilitest.com/system-usability-scale
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.