Scroll Top

Usability in CRO – The System Usability Scale (SUS)

So, you want to better understand your site’s usability. Can the System Usability Scale (SUS) help you?

To understand why you might want to use the System Usability Scale, you first need to understand:

  • What usability is,
  • What the System Usability Scale is,
  • What it can reveal, (and)
  • What it can’t

Already know the SUS is for you?

Explaining Usability

Usability refers to a user’s (or person’s) ability to use a product or service effectively to achieve a goal. Increasing usability increases ease and reduces the time it takes to achieve a goal. 

In the case of a website, good usability means a website visitor can smoothly move through the user flow towards their desired goal, (such as finding a desired product and completing a purchase).

Whilst there are many elements that impact whether a user continues their journey (including persuasive copy, communicative imagery, reassurances etc.), usability is essential alongside these, and can make or break an otherwise effective web strategy.

The importance of usability

Usability is the second level in user experience, after utility and before desirability and brand design. Therefore, once the product or service has been validated that it can solve a user’s problem, the next problem to address is its usability, so users are able to access this validated offering.

Desirability and brand design, (although important), are not going to result in conversion by themselves. If the user can’t find their way through your user flow or find the information they need, they will leave. We see this a lot with sites that are design-led rather than CRO-led. They are beautiful to look at, but their conversion rate is extremely poor.

By tackling your site’s usability, you’re making an important step towards a great user experience, and ultimately satisfying your users’ needs.

Why you might use the System Usability Scale

Ineffective usability is one of the biggest reasons for loss of conversions. When your website user flow isn’t clear, users are likely to get frustrated and will pursue their goals elsewhere. Even highly motivated customers can be dissuaded by a single bad experience on your site.

According to the Fogg Behaviour model, two key factors affecting conversions are motivation and ability. Whilst we can’t control someone’s motivations (only reinforce them), we can most definitely control their ability by ensuring optimum usability throughout the site.

Usage of the System Usability Scale

The System Usability Scale is a widely used tool for understanding and optimising a site’s usability. It comes into its own on sites where usability is much more important than persuasion. For example, if someone must use a government website, then making it as easy and quick as possible is one of (few) priorities when it comes to design.

In the private sector, users have more choice. If someone has a choice of where to shop and you run an ecommerce store, then you need to persuade them to shop with you rather than a competitor. Making your site easy to use isn’t enough, but it is a great place to start.  

A proven, dependable method of gathering legitimate and reliable data, this system has stood the test of time for a reason. When compared to in-depth user testing, it is very low-cost and quick.

Origins of the System Usability Scale

The System Usability Scale was devised almost 40 years ago as a “reliable, low-cost usability scale that can be used for global assessments of systems usability”. Quite a bold claim for a questionnaire from 1986 – the same year as both the first portable laptop and the first computer virus.

The System Usability Scale appears when companies such as IBM are only just setting up their websites. It is understandable therefore to view the scale as incompatible with modern technologies.

Although technology and what we need from it has massively changed since the System Usability Scale’s inception in 1986, usability’s focus on the way people understand and interact with a product or service to achieve a goal remains relevant.

Effective usability relies on peoples’ natural understanding of any system. Systems which measure usability such as the System Usability Scale, become applicable in any scenario involving human-technological interaction, such as websites.

Because websites can be accessed anywhere, it makes the System Usability Scale an even easier to implement research method than when it was used on physical technology.

Limitations of the System Usability Scale

The System Usability Scale was a test originally administered following recorded user-sessions to identify which users may have struggled. The footage would be reviewed alongside the results which can take a considerable amount of time. It wasn’t intended as a standalone test.

On its own, the test doesn’t reveal why users are having problems, it only provides a benchmark for the effectiveness of a site’s usability. Therefore, despite its widespread use, it may not provide you with the answers to WHY people are struggling on your site.

It will also not tell you accurately how likely users are to convert. A user may find your user flow very simple to navigate, but feel uneasy due to a lack of trust factors or unmotivated to convert due to a lack of persuasive copy and imagery.

For this reason, using a System Usability Scale may not be the most appropriate next step, as on its own, it doesn’t reveal particularly actionable insights.

System Usability Scale Guide

The System Usability Scale questionnaire is made of 10 statements which users respond to using the ‘Likert scale’ (often called the ‘rating scale’). Users choose one of 5 options to indicate their level of agreement with these statements, ranging from ‘strongly disagree’ (1), to ‘strongly agree’ (5).

System Usability Scale Questions

In the questions below, “system” or “product” can be used interchangeably according to the context of your offering. It can also be substituted for “website” to make it clearer to your participants.


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 have found the various functions in this system were well integrated

6.     I thought there was too much inconsistency in the platform

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

System Usability Scale Template

Get your printable download of the System Usability Scale (includes scoring guide and benchmark data). 

    Scoring System Usability Scale results

    1. For odd numbered questions, subtract one from the user’s selected score.

    2. For even numbered questions, subtract the user’s selected score from 5.

    3. Each question should now have a score of 0-4.

    4. Add these up and multiply the total score by 2.5 to receive a final score out of 100.

    Benchmarks for system usability scale scores

    The Jeff Sauro grading scale states that a system usability score of 68 is a universal ‘average’ and is equivalent to a letter grade ‘C’.

    Although any score above a 68 can be considered ‘above average’, it is common within industrial applications to strive for a system usability score of 80 – an ‘A-‘ on the scale below.

    The table shown below is a reproduction of one produced by Jeff Sauro, PhD.

    Next Steps

    Although a widely used and trusted method of user research, the System Usability Scale is limited in its ability to reveal the insights and next steps that you need to improve your user experience.

    Combined with more thorough research, this scale can be used to gather valuable insights from real users. However, this sort of thorough user research is very time-consuming and costly – the opposite of why most people try to use the System Usability Scale, (for quick and cost-effective testing).

    You SHOULD use the System Usability Scale if you are trying to gather an understanding of your site’s usability and are comfortable with having little to no knowledge as to why you received this score. This can be helpful if you are redesigning the user flow and are comparing one version with another. The System Usability Scale could also be useful for making comparisons between your website and competitor sites.

    If you’re looking for real, usable insights into your site (without the time implication that is thorough user research), a CRO Audit can give you what you need. Undertaken by professionals in user research and conversion rate optimisation, a CRO Audit uses a combined 30+ years’ experience in optimising websites for conversion to present you with clear, actionable findings.