Score your product’s usability in minutes.
Bring your participants’ answers and get the overall SUS score, letter grade, percentile and a per-question breakdown. The whole System Usability Scale, done for you.
Free to start. No card.
Good65th percentile
One number for “how usable is it?”
The System Usability Scale is a ten-statement questionnaire run at the end of a usability session. It measures how usable people find a product, with two sub-scores: Usability and Learnability. It won’t tell you why something is hard to use, but it tells you, dependably, whether it is.
By hand, in a spreadsheet
Every study starts the same way.
- Flip the even-numbered items one by one
- Sum, scale and average across participants
- Look up the grade and percentile in a table
With the calculator
Answers in, readings out.
- Import everyone's answers or share a link
- Score, grade and percentile in one view
- Sub-scores and a per-question breakdown
What you get back.
Your result
The overall SUS score from 0 to 100, with its letter grade, percentile and adjective rating.
Why it scored that
Usability and Learnability sub-scores, the spread of participant scores, and how everyone answered each statement.
Every way to collect answers
Enter them by hand, import a CSV or XLSX, or share a link to the questionnaire.
Example · answers by question
- Q1 Would use it often
- Q2 Unnecessarily complex
- Q3 Easy to use
- Q4 Needs technical support
- Q5 Functions well integrated
- Q6 Too inconsistent
- Q7 Quick to learn
- Q8 Cumbersome
- Q9 Felt confident
- Q10 Lots to learn first
Go deeper with Pro
Pro- Reliability (Cronbach's α)
- A 95% confidence interval on your score
- Outlier detection
- Benchmarks by product type
- Breakdowns by age, region and education
- More rounds, and a shareable PDF
The ten statements behind the score
Each is answered from 1 (strongly disagree) to 5 (strongly agree). Odd items are positive and even items negative, and the scoring handles the alternation for you.
- 1I think I would like to use the system frequently.
- 2I found the system unnecessarily complex.
- 3I thought the system was easy to use.
- 4I think that I would need the support of a technical person to be able to use the system.
- 5I found the various functions in the system were well integrated.
- 6I thought there was too much inconsistency in the system.
- 7I would imagine that most people would learn to use the system very quickly.
- 8I found the system very cumbersome to use.
- 9I felt very confident using the system.
- 10I needed to learn a lot of things before I could get going with the system.
From answers to a grade.
The tool scores every participant, averages them, and reads the result on this scale.
F
Below 60
Real usability problems.
D
60 to 70
OK, but marginal.
C
70 to 80
Good and acceptable. Above the 68 average.
B
80 to 90
Excellent.
A
90 to 100
Best imaginable.
68 is the benchmark average reported by Sauro and Lewis. Below 58 the tool also reads the result as not acceptable, and from 70 as acceptable.
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Free
- Every tool, in full (free plan limits apply)
- One project per tool
- One survey round, up to 25 responses
Pro
for your first 3 months, then €29/mo.
- Unlimited projects
- Unlimited survey rounds & responses
- Historical trends across rounds
- AI coach & assisted canvases across the framework
Rather have it done for you?
Book an AI-UX audit: find where users lose trust, and get a blueprint to fix it.
Before you start
What is the System Usability Scale?
The SUS is a 10-item questionnaire that gives a single, reliable 0 to 100 measure of how usable people find a product. It is one of the most widely used, best-validated UX metrics, quick to run and easy to benchmark over time.
How is the SUS score calculated?
Each item is answered 1 to 5. For positively worded items the score is (answer - 1); for negatively worded items it is (5 - answer). Sum the ten and multiply by 2.5 for a 0 to 100 score. The benchmark average reported by Sauro and Lewis is about 68.
What is a good SUS score?
68 is the benchmark average. In this tool's grade scale, 90 and above is an A, 80 to 90 a B, 70 to 80 a C, 60 to 70 a D and below 60 an F. The tool also gives you a percentile, an acceptability rating, and an adjective from Worst imaginable to Best imaginable.
How many participants do I need?
SUS is unusually robust at small sizes, but precision grows with your sample. 5 to 8 participants is a rough, formative read, so interpret it cautiously. 12 to 15 gives a reasonably stable mean for internal decisions. 30 or more gives tighter confidence intervals, benchmarking and comparisons over time. Always report the sample size next to the score.
Using AI? Measure it too.
SUS tells you whether the interface is usable. It was built for software that behaves the same way every time. AI-UX Score covers what SUS was never designed to see: how much people trust your AI. Use both.
See the AI-UX Score →Run it yourself, or have your AI audited.
Calculate your SUS
Add your participants and read the score in minutes. Free to start, no card.
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