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System Usability Scale – A Tool for Measuring Usability, Backed Up by Research 10 June 2015 | Nathan Thomas

If you’re serious about measuring the User Experience of your website you need to start using the System Usability Scale (SUS).

The SUS will give you a clear, definite grade for the UX of your website. This means you’ll know exactly how well you’re doing compared to industry standards.

When you use the SUS you are benefitting from an enormous legacy of statistical data. The SUS was created by John Brooke in 1986, who originally labeled it a “quick and dirty” usability scale.

Quick it may be, but the System Usability Scale has been shown through almost 30 years of use to be a reliable way of evaluating the usability of pretty much any system, websites very much included.

The SUS gives you statistically valid data; this means that if you administer this survey to the users of your website the results you receive will give you a clear answer to a clear question: Does your website have positive user experience?

Here’s How it Works:

The SUS includes 10 questions which you will ask your users to complete. Users answer each question by ranking from 1 to 5. 1 means they strongly disagree, 5 means they strongly agree, and 2 and 3 are somewhere in the middle.

Here are the 10 template questions:

  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.

Here’s a live demo of the SUS in action: click here

How to Add Up the Score

Adding up SUS scores can be a bit tricky, but once you get the hang of it it comes a lot easier..

So, you’ve sent people the test and they have ranked each question from 1 to 5.

For all the odd numbered questions above you subtract one from the score. 1 becomes 0, 3 becomes 2, and 5 becomes 4.

For all the even number questions above, you subtract the response FROM 5. So, if they ranked a question as a 2, you would go 5-2, which is, of course, 3. If they gave a 4, you would calculate 5-4.

Once you’ve processed each of the results with these formulas, you add up the total score with the new numbers and then multiply this by 2.5. This gives you a total possible score out of 100.

Seem A Bit Complex?

We agree. So we’ve created a simple Excel Spreadsheet for you which does all the calculations for you.

Simply plug in your numbers and you’ll be given your UX score automatically. Here’s the link to the spreadsheet on Google Docs:

System Usability Scale Calculator

It contains example scores, and after you’ve run your own SUS test you can simply input your data and it will process your SUS score.

The Average SUS Score is 68.

This means that if your score is BELOW 68, then you’ve got work to do. If it’s around 68 then you’re doing OK, and if it’s high above 68 then congratulations, your website is delivering an excellent user experience; good job!

Here’s what your grades will look like:

  • 80.3 or higher is an A. People love your site and will recommend it to their friends
  • 68 or thereabouts gets you a C. You’re doing OK but could improve
  • 51 or under gets you a big fat F. Make UX your priority now and fix this fast.

How to Use the SUS

Most people use the System Usability Scale to get an simple answer to whether or not their website (or any system) is delivering a good UX.

After your users experience your system you give them the SUS survey.

SUS Basic Final

Based on this answer you can decide how much money and time to invest in re-doing your website and making improvements to the user experience.

Get creative, though, and there are other ways to use this system.

Let’s say your company is debating between two different website designs, and isn’t sure which to go with.

You can ask a handful of your subscribers to take the SUS for version A, and another handful to take the SUS for version B. The version that has the highest SUS is probably the best version to run with because this delivers the most enjoyable and satisfactory user experience to your prospects.

SUS Compare Final

Comparing the two scores it will be obvious which option delivers the best user experience, so your decision will be easy.

How to Start Getting Results Now

The User Experience Suite comes with the SUS pre-loaded as a template, so we’ve already done all the hard work for you.

You can get responses in two ways:

  1. Send this survey to your subscribers using a simple link,
  2. Use our paid panel integration which gives you access to millions of respondents worldwide to get actionable data within hours.

To get started now, create your free account with UsabilityTools by Clicking Here.

Nathan Thomas

Written by Nathan Thomas

Nathan started his first online business whilst still in high school. When he's not helping companies reach more people on the internet, he enjoys exploring the world and writing about travel on his blog, Intrepid Times

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