Making the System Usability Scale Work
Perspective

Making the System Usability Scale Work

The SUS is a highly flexible tool, but positioning is everything. At Cloudberry, we’ve uncovered subtle factors that can make or break your SUS results.

By observing how 5–10 users perform key tasks, we can uncover patterns in comfort, confidence, and ease of use. But conducting the research and translating those behavioral insights into something tangible for clients isn’t always straightforward. The SUS distills complex experiences into a single, actionable score. Still, it presents its own challenges.

What is the SUS?

Conceptualized in 1986 by engineer John Brooke, the SUS is a 10-item questionnaire that users complete after interacting with a system. It quickly went viral and has since become the unofficial “official” standard for measuring usability. It is essentially a variation of the Likert Scale in which users are given a set of 10 statements and are asked to rate them on a scale from 1 (strongly disagree) to 5 (strongly agree)
(1). The questions alternate between positive and negative statements to reduce bias.

  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.

The beauty of the scale is that it is extremely flexible: it can be applied to really any kind of product, from a mobile app to automobiles. The surveyed results are then quantified into a score of 40 and multiplied by 2.5 to become a score out of 100. Our clients use this number as a summary of the testing results rather than cobbling together a series of observations. Generally, anything above a 68 is considered usable. Easy enough, right?

The beauty of the scale is that it is extremely flexible: it can be applied to really any kind of product, from a mobile app to automobiles.

The Challenges of the SUS

We love the simplicity of the SUS but have noticed some pain points. Acknowledging these issues, especially during the testing results summary, is critical.

Challenge #1: Timing is everything

The SUS was designed to assess fully realized products, yet teams often apply it to early-stage prototypes. This risks capturing first impressions rather than informed ones (a classic example of “availability bias”).

Solution: When applying SUS to a prototype, the prototype should be in or nearing its final stages. If given too soon, users will respond only to the system in front of them – not how they think the final product will eventually look.

Challenge #2: When wording gets tricky

One of the strengths of the SUS is its simplicity — but sometimes the wording gets in the way. We’ve seen users pause or stumble over terms like “cumbersome.” Others get tripped up by the way the statements switch back and forth between positive and negative phrasing. This creates mental friction. Instead of focusing on their actual experience with the product, users start focusing on decoding the question. This is not only going to affect the rating but also could place users in an embarrassing situation.

Solution: Make the language simpler and the tone consistent. When questions are easier to understand, people spend less mental energy interpreting them and more energy reflecting on their actual experience. That means better data and more respectful design. Even founder John Brooke is open to adapting the SUS. In a 25-year retrospective, he wrote:
If I was starting out again, I might do things differently … I would have to decide whether user errors outweigh response biases. As it is, ‘SUS Classic’ now has a mass of research to support it, but there’s always the option of using an ‘all positive SUS’ if you worry about user errors.

Challenge #3: The SUS score becomes the story

The SUS score is easy to grasp — and that’s both its magic and its risk. Clients love having a clear metric. But behavioral science reminds us: once something is measured, it often becomes the goal (hello, Goodhart’s Law). Teams can become overly fixated on hitting a “good” SUS score, sometimes at the expense of qualitative nuance.

Solution: Position the SUS not as the final answer, but as a catalyst for better questions. Use it to guide decision-making, pair it with user narratives to paint the full picture.

We’re always looking for ways to improve our testing process. By strategizing when we use the SUS, how we present it to users and summarize it to our clients, we strive to get the most meaningful results possible.

Because the SUS, by nature, is “quick and dirty” in revealing conclusions, the structure can and should be adjustable.

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