SUS Score Calculator
Calculate the System Usability Scale (SUS) score for your product or service using this professional calculator. The SUS score provides a reliable measure of perceived usability.
Survey Responses
Enter the responses from your 10-question SUS survey (1-5 scale). For odd-numbered questions (1,3,5,7,9), 1=Strongly Disagree, 5=Strongly Agree. For even-numbered questions (2,4,6,8,10), 1=Strongly Agree, 5=Strongly Disagree.
Your SUS Score Results
Raw SUS Score:
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Normalized SUS Score (0-100):
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Usability Grade:
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Percentile Rank:
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Comprehensive Guide: How to Calculate SUS Score
The System Usability Scale (SUS) is a standardized questionnaire developed by John Brooke in 1986 to measure the perceived usability of a system, product, or service. With just 10 questions using a 5-point Likert scale, SUS provides a reliable, low-cost method for assessing usability that can be used with small sample sizes (as few as 8-12 users) while still providing statistically significant results.
Why Use SUS?
The SUS offers several key advantages:
- Standardized: Allows for benchmarking against other products and industry standards
- Reliable: Produces consistent results even with small sample sizes
- Valid: Correlates well with other usability measures
- Sensitive: Can detect small improvements in usability
- Technology-agnostic: Works for any type of system or interface
- Quick to administer: Takes users only about 2-3 minutes to complete
The 10 Standard SUS Questions
The SUS consists of the following 10 questions, presented in a fixed order with alternating positive and negative phrasing:
- I think that I would like to use this system frequently.
- I found the system unnecessarily complex.
- I thought the system was easy to use.
- I think that I would need the support of a technical person to be able to use this system.
- I found the various functions in this system were well integrated.
- I thought there was too much inconsistency in this system.
- I would imagine that most people would learn to use this system very quickly.
- I found the system very cumbersome to use.
- I felt very confident using the system.
- I needed to learn a lot of things before I could get going with this system.
How to Score SUS
The SUS scoring process involves several steps:
- Collect Responses: Have users complete the 10-item questionnaire using a 5-point scale (1=Strongly Disagree to 5=Strongly Agree for odd-numbered items; reversed for even-numbered items).
- Adjust Scores: For odd-numbered questions (1,3,5,7,9), subtract 1 from the user’s response. For even-numbered questions (2,4,6,8,10), subtract the response from 5.
- Sum Scores: Add up all the adjusted scores from the 10 questions.
- Calculate Total: Multiply the sum by 2.5 to convert the score to a 0-100 scale.
| Question | User Response | Adjusted Score |
|---|---|---|
| 1. I think that I would like to use this system frequently. | 4 | 4 – 1 = 3 |
| 2. I found the system unnecessarily complex. | 2 | 5 – 2 = 3 |
| 3. I thought the system was easy to use. | 5 | 5 – 1 = 4 |
| 4. I think that I would need technical support. | 1 | 5 – 1 = 4 |
| 5. I found the various functions well integrated. | 3 | 3 – 1 = 2 |
| 6. I thought there was too much inconsistency. | 3 | 5 – 3 = 2 |
| 7. Most people would learn quickly. | 4 | 4 – 1 = 3 |
| 8. I found the system cumbersome. | 2 | 5 – 2 = 3 |
| 9. I felt very confident using the system. | 5 | 5 – 1 = 4 |
| 10. I needed to learn a lot before using. | 1 | 5 – 1 = 4 |
| Sum of Adjusted Scores | 32 | |
| SUS Score (Sum × 2.5) | 80 | |
Interpreting SUS Scores
SUS scores range from 0 to 100, with higher scores indicating better perceived usability. Here’s a general guide to interpreting SUS scores:
| Score Range | Usability Grade | Percentile Rank | Adjective Rating |
|---|---|---|---|
| 80.3+ | A+ | 96th-100th | Best Imaginable |
| 71.4-80.3 | A | 85th-95th | Excellent |
| 62.7-71.3 | B | 71st-84th | Good |
| 51.7-62.6 | C | 41st-70th | OK |
| 36.6-51.6 | D | 15th-40th | Poor |
| 0-36.5 | F | 0th-14th | Worst Imaginable |
Research shows that the average SUS score across all industries is approximately 68 (on the 0-100 scale), which corresponds to about the 50th percentile. Scores above 68 are considered above average, while scores below 68 are below average.
Advantages of Using SUS
The System Usability Scale offers several key benefits that make it one of the most popular usability measurement tools:
- Quick and Easy to Administer: The 10-item questionnaire typically takes users only 2-3 minutes to complete, making it practical to include in most usability testing sessions.
- Language Neutral: The questions are simple and can be easily translated into other languages while maintaining reliability.
- Sensitive to Small Changes: SUS can detect small improvements in usability, making it useful for iterative design processes.
- Standardized Scoring: The consistent scoring method allows for reliable comparison between different products and over time.
- Validated: Extensive research has demonstrated SUS’s validity and reliability across various industries and product types.
- Free to Use: Unlike some proprietary usability measures, SUS is completely free to use without any licensing requirements.
Limitations of SUS
While SUS is an extremely valuable tool, it’s important to be aware of its limitations:
- Not Diagnostic: SUS provides an overall usability score but doesn’t identify specific usability problems.
- Subjective Measure: It measures perceived usability rather than actual performance metrics.
- Context-Dependent: Scores should be interpreted in the context of the specific product and user group.
- Limited to 10 Items: The fixed set of questions may not cover all aspects of usability relevant to your specific product.
- Cultural Differences: Some research suggests that cultural factors may affect how users interpret and respond to the questions.
Best Practices for Using SUS
To get the most value from SUS, follow these best practices:
- Use the Standard Questions: Always use the original 10 questions in their exact wording and order to maintain validity and allow for benchmarking.
- Collect Enough Responses: Aim for at least 8-12 users per test to get reliable results, though more is better for statistical significance.
- Administer After Use: Have users complete the SUS questionnaire immediately after they’ve had a chance to use the system.
- Keep It Anonymous: Assure users their responses are anonymous to encourage honest feedback.
- Combine with Other Methods: Use SUS alongside other usability testing methods (like task success rates or time-on-task) for a more complete picture.
- Track Over Time: Use SUS repeatedly throughout the development process to track improvements in perceived usability.
- Benchmark Against Competitors: When possible, compare your SUS scores to industry benchmarks or competitor products.
SUS vs. Other Usability Metrics
While SUS is one of the most popular usability measurement tools, it’s helpful to understand how it compares to other common metrics:
| Metric | Type | Number of Items | Scale | Advantages | Limitations |
|---|---|---|---|---|---|
| System Usability Scale (SUS) | Subjective | 10 | 0-100 | Standardized, reliable with small samples, technology-agnostic | Not diagnostic, limited to perceived usability |
| Net Promoter Score (NPS) | Subjective | 1-2 | -100 to +100 | Simple, measures loyalty, industry benchmarks available | Not usability-specific, controversial methodology |
| Customer Satisfaction (CSAT) | Subjective | 1+ | Typically 1-5 or 1-7 | Simple, flexible, easy to understand | Not standardized, limited diagnostic value |
| Task Success Rate | Objective | Varies | 0%-100% | Direct measure of performance, actionable | Requires task definition, doesn’t measure satisfaction |
| Time-on-Task | Objective | Varies | Seconds/minutes | Quantitative, good for comparison | Can be affected by external factors, doesn’t measure satisfaction |
| USE Questionnaire | Subjective | 30 | 1-7 per item | More comprehensive than SUS, measures 4 dimensions | Longer to complete, more complex scoring |
Advanced SUS Applications
Beyond simple score calculation, there are several advanced ways to use SUS:
- Benchmarking: Compare your product’s SUS score against industry averages or competitor products. Many organizations publish SUS benchmarks for various product categories.
- Longitudinal Tracking: Use SUS repeatedly throughout the product development lifecycle to track improvements in perceived usability over time.
- Segment Analysis: Break down SUS scores by user segments (e.g., novices vs. experts, different demographic groups) to identify usability differences between groups.
- Correlation Analysis: Examine relationships between SUS scores and other metrics (e.g., task success rates, time-on-task) to gain deeper insights.
- Confidence Intervals: Calculate confidence intervals for your SUS scores to understand the range within which the “true” score likely falls, given your sample size.
- Statistical Testing: Use statistical tests (like t-tests) to determine if differences between SUS scores (e.g., before and after a redesign) are statistically significant.
Common Mistakes to Avoid
When using SUS, be careful to avoid these common pitfalls:
- Modifying the Questions: Changing the wording or order of questions can invalidate the standardized scoring and make benchmarking impossible.
- Using Non-Standard Scales: Always use the 1-5 scale as intended; don’t change to a different scale (e.g., 1-7 or 1-10).
- Skipping Questions: All 10 questions must be included for valid results.
- Improper Scoring: Remember that even-numbered questions require reverse scoring (subtract response from 5).
- Small Sample Sizes: While SUS works with small samples, very small samples (fewer than 8 users) may not provide reliable results.
- Ignoring Context: Don’t compare scores across vastly different products or user groups without considering context.
- Overinterpreting Small Differences: Small differences in SUS scores (e.g., 2-3 points) may not be practically significant.
- Using as the Sole Metric: SUS should be part of a broader usability evaluation, not the only metric used.
SUS in Academic Research
The System Usability Scale has been extensively studied in academic research. Key findings include:
- SUS is one of the most reliable standardized questionnaires for measuring perceived usability (Bangor et al., 2008).
- The questionnaire shows high internal consistency (Cronbach’s alpha typically > 0.9) across various studies.
- SUS scores are normally distributed, allowing for parametric statistical analysis.
- The scale is sensitive enough to detect usability improvements between design iterations.
- SUS correlates well with other usability metrics but provides unique information not captured by performance measures alone.
Research has also explored variations of SUS, including:
- Shortened versions (e.g., SUS-Quick with 8 items)
- Domain-specific adaptations (e.g., for healthcare or mobile applications)
- Cultural adaptations for non-English speaking users
- Versions for children and special populations
Implementing SUS in Your Organization
To successfully implement SUS in your organization:
- Educate Stakeholders: Explain what SUS measures and how to interpret the scores to get buy-in from decision-makers.
- Integrate into Processes: Incorporate SUS into your standard usability testing protocols and product development workflows.
- Establish Baselines: Conduct initial SUS evaluations to establish baseline scores for your products.
- Set Targets: Define realistic SUS score targets based on industry benchmarks and organizational goals.
- Track Over Time: Implement a system for tracking SUS scores across product versions and releases.
- Combine with Qualitative Data: Always collect qualitative feedback alongside SUS scores to understand the “why” behind the numbers.
- Report Results Effectively: Present SUS data in clear, actionable formats that highlight key insights and recommendations.
Future of SUS
As user experience research continues to evolve, we’re seeing several trends related to SUS:
- Automated Administration: More tools are integrating SUS into automated usability testing platforms.
- Real-time Feedback: Some organizations are experimenting with collecting SUS data continuously rather than just at the end of testing sessions.
- AI Analysis: Machine learning techniques are being applied to analyze SUS data in combination with other metrics for deeper insights.
- Micro-SUS: Researchers are exploring ultra-short versions of SUS for quick pulse checks on usability.
- Emotional SUS: Some variants are being developed that incorporate emotional response measurements alongside the standard questions.
- Predictive Modeling: SUS scores are being used to build predictive models of user behavior and product success.
Despite these innovations, the original 10-item SUS remains the gold standard for measuring perceived usability due to its simplicity, reliability, and extensive validation across industries.