What a SUS Score of 72 Actually Means
A team's post-launch survey returns a System Usability Scale (SUS) score of 72. Someone on the team says, "that's basically a 72%, so a C grade at best."
Is that the correct way to read a SUS score of 72?
The correct answer is "No — it's above the ~68 average SUS score, not a percentage."
SUS produces a 0-100 score, but it isn't a percentage of anything and shouldn't be graded like a test. It's meant to be read against the distribution of SUS scores collected across hundreds of real studies — Bangor, Kortum, and Miller's widely cited benchmark research puts the average score at roughly 68. A score of 72 is therefore modestly above average perceived usability relative to other SUS-tested products, not a middling "C" — reading it as a raw percentage badly understates how the product actually compares.
The distractors describe plausible-sounding but wrong readings: SUS is not scored or interpreted as a percentage of tasks completed (it's an attitudinal questionnaire, not a task-success measure); a bare score is genuinely under-informative without the benchmark, but that's an argument for citing the ~68 average, not for treating the score as meaningless; and there's no fixed pass/fail cutoff at 70 — the "poor" range starts closer to 51, well below where 72 sits.
Share this question