System Usability Scale (SUS): Improving Products Since 1986

Aug 29, 2014

Trying to measure usability can be a head scratcher. How easy something is to use depends on where you are, who you are, and a number of other factors. Luckily in the world of usability, there exists a post-test survey known as the System Usability Scale, introduced in 1986 by an engineer named John Brooke, who was trying to solve this very dilemma.

System Usability Scale, question 1: I think that I would like to use this system frequently. On a scale of 1 to 5, with 1 being Strongly disagree and 5 being Strongly agree, number 2 is checked for the answer.

The SUS is no stranger to federal agencies. GSA and OPM are just two of the many agencies that use the SUS as a post-test assessment of how easy a product is to use. Since it was unleashed on the world, the SUS has been used in over 1,200 published tests, encompassing a wide range of services and products, many of which did not even exist at the time the survey was created!

The System Usability Scale he created asks users their opinion on how easy something is to use by agreeing or disagreeing with 10 statements. Users take the survey immediately after completing a usability test, and statements alternate between positive and negative statements so respondents don’t go on autopilot when checking off answers.

Here’s what an SUS looks like:

System Usability Scale Questionnaire

  1. I think 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.

Customizable Questions

By alternating negative and positive statements, the SUS questions make people think hard about the experience; it prevents them from just saying “Yeah, it was great” the whole way down. Another great thing: You can tweak the wording or order to meet your needs without worrying about affecting the results. Even when the exact wording of the original survey is not used, the results are still very reliable.

System Usability Scale graphic fonts

Maybe you want to know if people think the smartphone app you created to help fill out taxes is easy to use. After testers finish trying to use the app, you can tack on a SUS survey at the end and substitute the original questionnaire wording “system” for “mobile app.” Voila! You have created a System Usability Scale survey for your specific product.

Even though the SUS is turning a mature 28 years old this year, its accuracy, reliability, and utility is a good indication that this survey will be around for many years to come.

Georgia Gallavin is in her last semester at The New School in New York City, earning an MA in Media Studies. She recently finished her internship with the DigitalGov User Experience Program at GSA.