The System Usability Scale (SUS) measures people’s subjective perceptions of the usability and learnability of a system in a very short amount of time on a small sample size. SUS scores can also be used to compare differences between old and new experiences of your product (or your product vs. a competitor’s). > **Note:** SUS Scores alone are not diagnostic, and may not reveal a specific problem with your product or feature. SUS provides a good measure of the usability and learnability compared to some industry benchmarks. ## When to calculate SUS - Before and after redesigns - For new users, or new features for existing users, for closed beta users - Comparing your product to a competitor’s - Generating a usability baseline of your existing product ## Audience It’s best to survey users that are newer to the product or feature rather than long-term users, as you want to capture their perception of its usability and learnability. ## Requirements 1. Minimum of 5 respondents (and can scale up to hundreds or thousands). 2. Respondents should be relatively new to the product, service, or feature being tested. 3. Description of product, service, or feature … 1. (example) ## Deliverables - Insights into how your system compares to industry standards (or previous SUS Scores for your system). - Conversion of SUS Score to Percentile Rank - The overall SUS, Usability, and Learnability scores - Breakdown of each respondent’s individual answers, their SUS Score, Usability Score, and Learnability Score. ## SUS Questions A SUS survey consists of 10 questions with responses based on a Likert scale: 1. I think that I would like to use this system frequently. 2. I found the system unnecessarily complex. 3. I thought the system was easy to use. 4. I think that I would need the support of a technical person to be able to use this system. 5. I found the various functions in this system were well integrated. 6. I thought there was too much inconsistency in this system. 7. I would imagine that most people would learn to use this system very quickly. 8. I found the system very cumbersome to use. 9. I felt very confident using the system. 10. I needed to learn a lot of things before I could get going with this system. ## Calculating the SUS Score 1. For odd-numbered questions, subtract `1` from the 1–5 response (`X-1`). 2. For even-numbered questions, subtract the 1–5 response from `5` (`5-X`). 3. Sum the scores from all questions, then multiply the total by 2.5 (`Total * 2.5`). - Scores for each question can be between 0–4. - Resulting SUS Scores range from 0–100, with an average score of 68. - Note: Scores are *not* percentages, though. 68 is the average SUS Score, which falls right at the 50th percentile. 4. This will produce a usability score for the product/feature, which product teams can use to compare between the old and new experiences or between the competitor’s and your own designs. ## SUS Score Interpretation \> 80.3 = A (Excellent) 68–80.3 = B (Good) 68 = C (Okay) 51–68 D (Poor) < 51 F (Awful) ## Calculating Learnability & Usability In addition to the overall SUS Score, we can also measure the perceived usability and learnability of the system. - Questions 4 and 10 provide the dimension for learnability. - All other questions (1, 2, 3, 5, 6, 7, 8, 9) provide the dimension for usability. --- ## Resources - [MeasuringU: 10 Things to Know About the System Usability Scale (SUS)](https://measuringu.com/10-things-sus/) - [MeasuringU: SUS Guide & Calculator Package](https://measuringu.com/product/suspack/) - [SUScalculator.wmv - YouTube](https://www.youtube.com/watch?v=w_Rul2M1ApY) - [How to Measure Product Usability with the System Usability Scale (SUS) Score | by Hadi Alathas | UX Planet](https://uxplanet.org/how-to-measure-product-usability-with-the-system-usability-scale-sus-score-69f3875b858f) - [Calculating SUS Score With Google Form - YouTube](https://www.youtube.com/watch?v=7OJjJevg1xk) - [SUS: A RetrospectiveJUS](https://uxpajournal.org/sus-a-retrospective/) - [System Usability Scale Template (Google Sheet)](https://docs.google.com/spreadsheets/d/1hn-gV83Lsw78P7Z_ipmyocx6mOy-8WfLYuTvd4g3Mbw/edit#gid=551149634) - [Rank your product](https://medium.com/uxpress/quantify-with-some-standardized-usability-tests-3a69f6746c63) - [The System Usability Scale (SUS) (Video by NNgroup)](https://www.nngroup.com/videos/system-usability-scale/)