Understanding the System Usability Scale (SUS): 10‑Question Survey and Scoring Method

Form: A standardized questionnaire containing 10 statements.

Scoring: Each statement is rated on a 5‑point Likert scale (1 = Strongly disagree, 5 = Strongly agree). For odd‑numbered (positive) items, score = response − 1; for even‑numbered (negative) items, score = 5 − response. The transformed scores are summed and multiplied by 2.5 to produce a 0–100 SUS score.

Example calculation: If a user selects 5, 2, 4, 1, 5, 2, 5, 1, 4, 2 for items 1‑10, the transformed scores become 4, 3, 3, 4, 4, 3, 4, 4, 3, 3, totaling 35. 35 × 2.5 = 87.5, yielding an SUS of 87.5.

Interpretation ranges (Brooke 1986):

0–50: Unacceptable, severe usability problems.

50–70: Marginally usable, noticeable issues.

70–80: Acceptable, average industry level.

80–90: Good, above‑average user experience.

90–100: Excellent, benchmark quality.

The typical industry average SUS score is around 68; scores above this indicate usability better than average.

Time to complete: Most users finish the questionnaire in 1–2 minutes.