A standardized 10-question survey that measures perceived usability on a 0–100 scale. The SUS is quick to administer, technology-agnostic, and has been validated against other usability measures, making it a reliable benchmark for comparing products or tracking improvement over time.
Common contexts
- Appending to every moderated usability session to build a longitudinal score database across releases
- Comparing SUS scores between the current product and a prototype to justify a design direction to stakeholders
- Measuring perceived usability across different user segments to identify which audience struggles most
Use when
Use SUS at the end of any usability session or study when you want a quick, validated measure of perceived usability that travels well across projects and teams. It costs users under two minutes and gives you a score you can trend across releases — making it worth including almost by default.
Avoid when
Don't rely on SUS as your only usability evidence when presenting to an engineering team that needs specific, actionable problem areas to fix. A score of 62 tells them something is broken but gives them nothing to act on — pair it with task-level data or qualitative findings.
A score above 68 feels like a pass, but seasoned researchers know scores in the 68–75 range often mask one or two catastrophic flows that a small sample of satisfied power-users is averaging out.
Real-world examples
- Slack scored above 80 on SUS (adjective rating: 'Excellent') in independent benchmarks during their 2015–2018 growth phase, a score their growth team cited when pitching enterprise customers who demanded usability evidence.
- Healthcare.gov scored below 50 on SUS after its disastrous 2013 launch — below the 68 'average' threshold — providing designers with a defensible benchmark for justifying a complete rebuild to Congress.
- John Brooke designed SUS to be technology-agnostic: it has been validly applied to websites, hardware devices, physical products, and voice interfaces, making it the most widely-used single-metric usability scale in industry.