1. What is the System Usability Scale?
The System Usability Scale (SUS) is a ten-item questionnaire developed by John Brooke in 1986 that measures the perceived usability of a digital application. Despite its brevity, SUS is considered one of the most robust and most widely validated usability metrics — with just 10 items, it delivers a single, comparable score from 0 to 100.
SUS is method-agnostic: it works for websites, mobile apps, enterprise software, hardware interfaces, and even voice UIs. That makes it the standard tool whenever teams want to compare versions, competitors, or releases.
2. The SUS Questionnaire
Participants rate ten statements on a 5-point Likert scale from 1 = strongly disagree to 5 = strongly agree. Odd-numbered items are worded positively, even-numbered items negatively — this prevents acquiescence bias.
- Q1 (+) I think that I would like to use this system frequently.
- Q2 (−) I found the system unnecessarily complex.
- Q3 (+) I thought the system was easy to use.
- Q4 (−) I think that I would need the support of a technical person to be able to use this system.
- Q5 (+) I found the various functions in this system were well integrated.
- Q6 (−) I thought there was too much inconsistency in this system.
- Q7 (+) I would imagine that most people would learn to use this system very quickly.
- Q8 (−) I found the system very cumbersome to use.
- Q9 (+) I felt very confident using the system.
- Q10 (−) I needed to learn a lot of things before I could get going with this system.
3. Calculating the SUS Score
- For odd-numbered items (positive): response value minus 1.
- For even-numbered items (negative): 5 minus the response value.
- Multiply the sum of all 10 transformed values by 2.5.
The result: a score between 0 and 100. Important: the SUS score is not a percentage — 68 doesn't mean "68% usability," it roughly corresponds to the average across all systems ever measured.
4. Benchmarks & Interpretation
According to Sauro & Lewis (2016), SUS scores can be translated into a letter-grade scale:
| SUS Score | Grade | Meaning |
|---|---|---|
| > 80.3 | A | Excellent — users would actively recommend it |
| 68–80.3 | B / C | Good to acceptable — above average |
| 51–68 | D | Below average — action needed |
| < 51 | F | Poor — fundamental usability problems |
The cross-industry average sits at around 68. Anything below that is a clear signal that users are experiencing friction.
5. When to Use SUS — and When Not To
Well suited for:
- Comparing versions (A/B releases, before/after).
- Competitive benchmarks against rival products.
- Quick pulse tracking across quarters.
- Studies with small samples (usable from ~12–15 participants).
Not suited for:
- Diagnosing why a system is unusable — for that you need qualitative interviews.
- Measuring individual features (SUS measures the overall experience).
- Early discovery phases where the product isn't testable yet.
6. Automating SUS with Konsoul
A classic SUS study typically costs a UX team 2–3 weeks: recruiting, distribution, reminders, data cleanup, score calculation, report. With Konsoul, Klymeo's AI agent, the same cycle runs in hours:
- Setup in plain language. You describe the target audience and the application to be tested to Konsoul — the questionnaire is instantiated with validated SUS logic.
- Recruiting & fieldwork. Konsoul selects matching participants from the Klymeo panel, sends invitations, and monitors quotas in real time.
- Score calculation. Every response is instantly transformed per the SUS formula; the mean score plus confidence interval is ready as soon as the quota is reached.
- Qualitative depth. Optionally, Konsoul asks for a brief rationale after each SUS item and clusters the open responses by theme — so you get not just the grade, but the reason behind it.
- Report & comparison. Benchmarks against earlier waves or competitor studies are calculated automatically and summarized in a shareable report — every statement evidenced in the transcript.