The 7 Most Important UX KPIs and How To Measure Them

The 7 Most Important UX KPIs and How To Measure Them

“What gets measured, gets managed”, said The American management thinker Peter Drucker. Unfortunately, this wisdom has not yet been fully leaked into the groundwater of the UX world. But without clear results and numbers, you’ll have a hard time positioning the UX issue with your superiors and getting more budget.

Do you want to slip away from the in-house role of Clarke Kent, and no longer just anonymously – that is, without clear evidence – perform your UX heroics for your organization? Do you want to create more acceptance and understanding for UX? Then you should read on.

From the outside, UX is usually associated with complex questionnaires and user interviews. However, there’s a whole bouquet of valuable UX performance indicators that you can use to pack the success and progress of your UX efforts into tangible metrics. We will introduce you to the seven most important ones in this article.

If you haven’t thought about what key performance indicators mean to you, you might want to read the following article first: What Are ROI and KPI?

The 7 most important UX KPIs

The UX KPIs are divided into so-called behavioral and attitudinal KPIs:

Behavioral UX KPIs (what they do)

The behavioral KPIs express in numbers what a user is doing effectively and how they interact with a product or website.

Nowadays, this data can usually be collected fully automatically without the intervention of an interviewer or observer. Ergo is a fairly simple and cost-effective way to start raising UX KPIs.

1. Task Success Rate

The Task Success Rate (TSR) measures the number of tasks performed correctly and is used very often in practice. If a task has a clearly defined endpoint—for example, filling out a form or purchasing a product—you can measure the TSR. However, you should be clear about which goals you consider a success in the specific case before you start collecting data.

Although the TSR says nothing about why a user does not perform a task successfully, it is a first, very valuable indicator.

For example, Ten subjects are given the task of ordering 10 red, 10 yellow, and 10 white roses each by express delivery and credit card payment in the webshop of a flower delivery service. Eight of the testers manage to perform the task successfully. Two testers don’t make it:

  • User 1: has problems with credit card payment.
  • User 2: cannot locate the yellow roses on the website.

In this case, the task success rate is calculated as follows:

8/10 = 0.8 x 100 = 80%

Pro tip: You should also measure the TSR of users performing a task for the first time. This allows you to check if or how this metric changes as the user has gained more experience with the service or product.

2. Time on Task

This KPI describes the time (in minutes and seconds) that a user needs to complete a task successfully. In most cases, the average time on task is communicated as the final UX KPI. Basically, the shorter the processing time, the better the user experience.

For example, Seven subjects are given the task of locating the customer service telephone number on a website. To do this, they need as long as possible:

User No. 1 2 3 4 5 6 7

The time on task is calculated as follows:

(22+15+60+24+18+31+17)/7= 26.71 seconds.

3. Search vs. Navigation

Navigation bars play an important instrument in the concert of websites: if a user does not manage to reach his destination via navigation, then the search function is usually the next logical step.

The less the search function is used, the better the customer experience in many cases. However, which ratio of the two metrics is more desirable in the specific case should always be defined individually. An example is a website with only 10 subpages, which usually has no search function and does not require any due to the existing clarity.

For example, You give 9 testers the task of ordering three sunflowers in the online shop of a florist. Then analyze how many users each use the navigation and search box.

User No.123456789#%

Calculation of the search/navigation ratio:

Search 3/9 = 0.33 x 100 = 33%

Navigation 6/9 = 0.66 x 100 = 66%

4. User Error Rate

The User Error Rate (UER) quantifies how often a user makes an incorrect entry. For example, the usually unsuccessful attempt to include his date of birth in the address field.

The UER gives you an impression of how clear and user-friendly your website is. The higher the UER score, the greater the usability problems. Here, too, it is important to define exactly which actions constitute a mistake.

The user error rate can be calculated in several ways. Here are the two most common measurement types:

Error Occurrence Rate: If a task allows only one potential error (or there are several and you only want to measure one of them), you should use this metric.

For example, 5 out of 100 users enter their email address incorrectly in the “Repeat email address” field. The Error Occurrence Rate is calculated as follows:

5/100 = 0.05 x 100 = 5%

Error Rate: If multiple errors are possible per task (or you want to measure more than one), you can do so using the error rate.

For example, Sixtesters have the task of making an international transfer in the online portal of a bank. The task has five error options and the user error number is distributed as follows:

User No.123456

The error rate is calculated as follows:

(3+1+2+3+2+1)/6×5= 0.4 x 100 = 40%

Attitudinal UX KPIs (what they say)

This type of UX KPIs measures how users feel or what they say before, during, or after buying a product. Below I present three prominent representatives of this species:

5. System Usability Scale (SUS)

The System Usability Scale (SUS) is a tool that allows you to test the usability of a product “quick and dirty” as its inventor John Brooke said. The scale consists of a 10-point questionnaire with five answer options each, ranging from a smattering of disagrees to strongly disagree.

For example, You want to measure the usability values of your website. using the questionnaire results, you can calculate the so-called SUS score (0 to 100), which is on average 68. If your website ergo scored under 68, it usually has serious flaws and should be optimized in any case.

Since the calculation of the SUS score is quite complicated, we would like to refer you to the excellent article by Seibert Media for more information.

6. Net Promoter Score (NPS)

The Net Promoter Score illustrates customer satisfaction and retention in a simple metric. Also, several studies have confirmed that the NPS is statistically relevant to the growth of a company.

The user is only asked a central question at the NPS:

How likely is it that you (brand, website, service, etc.) recommend it to a friend or colleague?

The user answers these on a scale from 1 (very unlikely) to 10 (very likely).

The answers are then grouped into three categories, not taking into account the “indifference” in the calculation:

  • Detractors: 0 to 6
  • Indifferent: 7 to 8
  • Promoters: 9 to 10

For example, A survey of 50 participants plays back the following results:

Detractors (0-6)10
Indifferent (7-8)10
Promoters (8-10)30

Here’s how the Net Promoter Score is calculated:

(30 – 10) ÷ 50 = 0.4 x 100 = 40%

7. Customer Satisfaction (CSAT)

The CSAT is another attitudinal UX KPI that reflects customer experience in a convenient metric. The user/tester is asked:

How satisfied are you with (website, product, service, etc.)?

The result is a percentage of 0 to 100, with 100 representing maximum customer satisfaction. The scale usually includes five evaluation options, ranging from very dissatisfied to very satisfied.

Customer Satisfaction (CSAT)

Since the CSAT score can be collected quickly and easily, it is also possible to measure them at several points of interaction with a customer (for example in the TOFU, MOFU, and BOFU phases. In this way, it is possible to determine where in the funnel it might still be “hooked”.

Customer Satisfaction: (number of satisfied customers) / number of respondents x100 = % of satisfied customers

The survey results are then classified and evaluated as follows:

  1. Very dissatisfied
  2. Dissatisfied
  3. Neutral
  4. Satisfied
  5. Very satisfied

For the calculation of the CSAT score only the answers of the satisfied users are counted, ergo the users who gave “satisfied” or “very satisfied” in response.

For example, After a successful purchase process, ten customers are asked how satisfied they are with the usability of your website and give the following answers:

User No.12345678910
Satisfied customersXXXXX

The CSAT score is calculated as follows:

(5 / 10) = 0.5 x 100 = 50%

Further information on the Customer Satisfaction Score can be found here.


With the UX KPIs featured in this article, you already have very powerful tools at your hands to finally translate the value of UX into the language of your colleagues and superiors.

It’s time for UX to get the value in your company that it deserves. And the sooner you start measuring, the faster you can slip into your Superman outfit.

Have you already defined UX KPIs for your organization? If so, what are the metrics you use and why? What has changed (positively) since you started measuring? How has your influence in the company developed since then?

If not, what keeps you from measuring? What would happen if you started measuring?


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