System Usability Scale

Created by John Brooke in 1986, System Usability Scale(SUS) is used to measure UI usability. It is one of the most frequently used measurement tools. Most of the cases utilize SUS to evaluate websites. However, it is also used to evaluate different systems ranging from mobile apps, kiosks to machinery.

The original SUS utilizes Likert scales from 1 to 5.

Step 1: Convert the scale into number for each of the 10 questions

• Strongly Disagree: 1 point

• Disagree: 2 points

• Neutral: 3 points

• Agree: 4 points

• Strongly Agree: 5 points

Step 2: Calculate

• X = Sum of the points for all odd-numbered questions – 5

• Y = 25 – Sum of the points for all even-numbered questions

• SUS Score = (X + Y) x 2.5