How to read Average Session Duration in Google Analytics

The Average Session duration is the average length of a Google Analytics session in a particular time period.

Following is the formula used by Google Analytics to calculate the average session duration in a particular time period:

Average Session Duration =

Total duration of all GA sessions (in seconds) in a particular time period / Total number of GA sessions in the same time period.

Consider following custom report of Google Analytics which shows number of GA sessions and average session duration for Direct Traffic:

Now I will show you, how Google Analytics calculated the Average Session Duration for Direct Traffic.

Apply a secondary dimension named ‘Session Duration’ to this report as shown below:

We can now see the duration (in seconds) for each GA session triggered by ‘direct traffic’.

Related Article: Complete Guide to Direct Traffic in Google Analytics

We can also conclude that majority of GA sessions triggered by ‘direct traffic’ have session duration of 0 seconds.

These 0 seconds duration sessions are the GA sessions in which Google Analytics wasn’t able to calculate the time spent by a user on your website.

It is not possible that a user visit your website and then leave it without spending even 1 second on the landing page (unless there is some tracking issue).

To make matter worse, these 0 seconds duration sessions are still used in the calculation of ‘Average Session Duration’ metric.

Because of this reason, the ‘Average Session Duration’ metric reported by Google Analytics is not reliable.

Get the E-book (52 Pages)

Get the E-Book (37 Pages)

Now let us see, how Google Analytics calculated the ‘Average Session Duration’ metric of 1 minute 40 seconds as reported below:

Let’s download this report into Google Spreadsheet for the purpose of calculating the average session duration metric manually:


Here,

Total duration of all GA sessions triggered by direct traffic = 3193 seconds

Total number of GA sessions triggered by direct traffic = 32

So,

Average Session Duration for Direct Traffic =

Total duration of all GA sessions triggered by direct traffic / Total number of GA sessions triggered by direct traffic

= 3193  / 32

= 99.78125 seconds

= 1 minute 40 Seconds

Google Analytics display 1 minute 40 Seconds as 00:01:40 and this average session duration matches average session duration reported by Google Analytics:

So we can conclude that our calculation of the ‘average session duration ‘ metric is correct.

But we also now know that the ‘average session duration ‘ metric reported by Google Analytics is not reliable.

So the better way to understand the average session duration of the sessions triggered by direct traffic is by visualizing the distribution of session duration for direct traffic.

To do that click on the ‘Performance’ button and then select ‘session duration’ from the drop down menu as shown below:

Following report visualize the distribution of session duration for Organic Search Traffic:

From this report we can conclude that majority of organic search sessions are of 0 second duration.

In other words for majority of organic search sessions, Google Analytics wasn’t able to calculate the time spent by a user on your website.

Because of this reason the ‘average session duration’ for organic search traffic, is a metric which can not be trusted.

A better way to understand the average session duration of organic search traffic is by visualizing the distribution of session duration for each organic traffic source (like google organic):

Average Session Duration for the website

Following is the formula used by Google Analytics to calculate the average session duration for the entire website in a particular time period:

Average Session Duration for a website =

Total duration of all GA sessions (in seconds) in a particular time period / Total number of GA sessions in the same time period.

Since majority of GA sessions are generally 0 second sessions and these sessions are also used in the ‘average session duration’ calculation, the Average Session duration’ for a website is totally unreliable.

You can see the Average Session duration for the entire website in the ‘Audience Overview’ report:

The rule of thumb is that before you read and draw conclusions from the ‘average session duration’ metric, segment it to is most granular level and then look at the distribution of session durations.

Why you should look at the distribution of data values in Google Analytics than trusting the average metric?

One big problem with average metric is that the presence of outliers (extreme values) can easily skew it.

For example consider the following data set:

1, 2, 3, 4, 20

Here the average is calculated as:

1+2+3+4+20 / 5 = 30/5 = 6

But this number 6 does not represent a typical value in the data set.

Because of this reason, the average can not be be trusted.

To calculate the correct average, we need to find and remove the outlier.

Here the outlier is 20.

So after removing this outlier, the average of the data set mentioned above would be:

1+2+3+4 / 4 = 10/4 = 2.5

When it comes to Google Analytics, the data sets that we deal are pretty large.

Because of this reason we can not easily find and remove outliers.

That’s why it becomes important to look at the distribution of data through data visualization.

Relationship between Average Session Duration and Bounce Rate

In case of Google Analytics, the average session duration tends to be inversely proportional to bounce rate i.e as bounce rate increases, the average session duration tends to go down and vice versa.

It is important to note that, I am not saying that that the average session duration always go down as bounce rate increases.

It tends to go down.

The chart below illustrate this relationship in real life scenario:

From the chart above we can conclude that as the bounce rate decreased over time the average session duration increased.

Now how this happened?

See if your website has got high bounce rate then most likely, Google Analytics is not able to track time spent on a web page in a single page session (session where user leave the website from the landing page without browsing further).

If you can fix this problem then GA will be able to calculate the time spent on a web page in single page sessions.

As a result, your 0 second sessions will decrease over time and your average session duration calculation will become more accurate.

And when this calculation becomes more accurate, you will start seeing a more accurate average session duration being reported which is most likely going to be higher than the one you see right now.

This will give you the impression that by reducing the bounce rate you increased the average session duration.

But what you actually did is started calculating the time spent on a web page in single page sessions.

When you have got few 0 second duration single page sessions, your bounce rate is likely to be very low.

You may see your bounce rate, going as low as zero.

But don’t worry about that.

Bounce rate is a vanity metric which most of the time does not reflect the true user behavior.

If you are calculating the time spent on a web page correctly then your bounce rate is going to be low.

 

Do you know the difference between Digital Analytics and Google Analytics?


99.99% of course creators themselves don’t know the difference between Digital analytics, Google Analytics (GA) and Google Tag Manager (GTM).

So they are teaching GA and GTM in the name of teaching Digital analytics.

They just copy each other. Monkey see, monkey do.

But Digital analytics is not about GA, GTM.

It is about analyzing and interpreting data, setting up goals, strategies and KPIs.

It’s about creating strategic roadmap for your business.


Digital Analytics is the core skill. Google Analytics is just a tool used to implement ‘Digital Analytics’.

You can also implement ‘Digital analytics’ via other tools like ‘adobe analytics’, ‘kissmetrics’ etc.

Using Google Analytics without the good understanding of ‘Digital analytics’ is like driving around in a car, in a big city without understanding the traffic rules and road signs.

You are either likely to end up somewhere other than your destination or you get involved in an accident.


You learn data analysis and interpretation from Digital analytics and not from Google Analytics.

The direction in which your analysis will move, will determine the direction in which your marketing campaigns and eventually your company will move to get the highest possible return on investment.

You get that direction from ‘Digital analytics’ and not from ‘Google Analytics’.


You learn to set up KPIs, strategies and measurement framework for your business from ‘Digital analytics’ and not from ‘Google Analytics’.

So if you are taking a course only on 'Google Analytics’, you are learning to use one of the tools of ‘Digital analytics’. You are not learning the ‘Digital analytics’ itself.

Since any person can learn to use Google Analytics in couple of weeks, you do no get any competitive advantage in the marketplace just by knowing GA.

You need to know lot more than GA in order to work in digital analytics and marketing field.


So what I have done, if you are interested, is I have put together a completely free training that will teach you exactly how I have been able to leverage digital analytics to generate floods of news sales and customers and how you can literally copy what I have done to get similar results.

Here what You'll Learn On This FREE Web Class!


1) The number 1 reason why most marketers and business owners are not able to scale their advertising and maximise sales.

2) Why you won’t get any competitive advantage in the marketplace just by knowing Google Analytics.

3) The number 1 reason why conversion optimization is not working for your business.

4) How to advertise on any marketing platform for FREE with an unlimited budget.

5) How to learn and master digital analytics in record time.

 
 

My best selling books on Digital Analytics and Conversion Optimization

Maths and Stats for Web Analytics and Conversion Optimization
This expert guide will teach you how to leverage the knowledge of maths and statistics in order to accurately interpret data and take actions, which can quickly improve the bottom-line of your online business.

Master the Essentials of Email Marketing Analytics
This book focuses solely on the ‘analytics’ that power your email marketing optimization program and will help you dramatically reduce your cost per acquisition and increase marketing ROI by tracking the performance of the various KPIs and metrics used for email marketing.

Attribution Modelling in Google Analytics and Beyond
Attribution modelling is the process of determining the most effective marketing channels for investment. This book has been written to help you implement attribution modelling. It will teach you how to leverage the knowledge of attribution modelling in order to allocate marketing budget and understand buying behaviour.

Attribution Modelling in Google Ads and Facebook
This book has been written to help you implement attribution modelling in Google Ads (Google AdWords) and Facebook. It will teach you, how to leverage the knowledge of attribution modelling in order to understand the customer purchasing journey and determine the most effective marketing channels for investment.

Himanshu Sharma

Digital Marketing Consultant and Founder of Optimizesmart.com

Himanshu helps business owners and marketing professionals in generating more sales and ROI by fixing their website tracking issues, helping them understand their true customers purchase journey and helping them determine the most effective marketing channels for investment.

He has over 12 years experience in digital analytics and digital marketing.

He was nominated for the Digital Analytics Association's Awards for Excellence.

The Digital Analytics Association is a world renowned not-for-profit association which helps organisations overcome the challenges of data acquisition and application.

He is the author of four best-selling books on analytics and conversion optimization:

error: Alert: Content is protected !!