How Long Should I Run An A/B Test For?

A/B tests are a necessity for any eCommerce business. They are a great way to generate engagement and to make sure that your outcomes are in alignment with your intentions. If you don’t test, you would never know if things could be more successful for your business. If you never test, then you never know.

Running the tests is crucial. But the next question is; how long should they run for in order to create the optimal results? The length of the test and the way you determine outcomes from these tests is important in order to reap the benefits. 

What Is An A/B Test?

A/B tests, also known as split tests, are a way of comparing at least two versions of a variable to determine specific results. For example, if you create two different landing pages to a website with certain differences (color, formatting, text), A/B tests can help you determine which one works better. This can be discovered through how users interact with the website, the usability and which leads to more sales.

Why Use An A/B Test?

It’s vital to run A/B tests because of all the valuable data it can provide you about your business. It actually allows you to optimize your whole business plan and model, saving money and time. This is because it shows you what your users want. It provinces access to knowledge about how best to achieve your business goals; and the results are tried and tested.

It’s one of the most efficient ways to gain insights into the demographics of your brand. It also shows you how best to reach your target audience, and where to focus your efforts moving forward. All of this, at a low cost and low risk strategy.

How Long Should I Run A/B Test For?

There are many factors that can help determine how long you run an A/B test. Some of these include:

The Type Of Test

If you’re running an email test, it might only run for a few hours or days because the email is sent once. After the email is sent you will see how users react. If shoppers will convert from the emails as soon as they encounter it. If not it will get lost in their inbox. 

However, if it’s a website test being run then this can be longer. Since there isn’t a contained or limited send or open time, you can keep it running. This allows you to see how users interact with it over an elongated period of time. 

Which Variants Are Being Tested

The more variants you test, the more traffic you need. This allows you to see the full scope of what is being demonstrated. You don’t want to spread your traffic too thin; different customers will be more interactive with different variables. 

If you have lower traffic in general, it’s a better idea to limit the number of variables to 2. This can make sure each version draws enough traffic that you could gain conclusive results within a reasonable timeframe.

Seasonal Factors

Throughout the year, according to the seasons, shoppers’ buying patterns change. For example, A/B testing over Black Friday/Cyber Monday could be risky, but would give you a high concentration of results in one go. At lower sales points, you might need to run a test for longer to receive the amount of traffic needed to get an accurate result.

Sales Cycles

Some industries follow distinctive sales patterns. For example, with higher ticket items certain sales can take a lot longer to go through all stages and then materialize. Leads might need to be nurtured for a longer period, therefore tests should be run longer. On the other hand, some may simply be quick purchase items, and small lengths of time spent on your store. Tests in these cases may be run for a shorter period of time.

Industry Best Practice

As we have seen, there are many factors that should be individually considered when choosing how long you run your test for. These should be specific to your website and your product. Having said that, there is an industry best practice. 

This is to run the test for a minimum of 2 weeks, but no longer than 6-8 weeks. 

This reduces the possibilities for anomalies, such as might occur if it is just over a one week period. The longer it is, the more validation and consistency you can see through results. Seeing the results of just one weekend might not be mirrored over the next one. It’s important to have a range of examples to draw upon.

On the other hand, if it’s longer than 6 weeks, it becomes harder to draw conclusions. User patterns may shift or cookies deleted, which makes variables change. Then it’s harder to see clearly what has actually happened. For example, has user patterns affected the results or something else?

On top of that, if tests run for too long then it can become more expensive. This could defeat the overall purpose of the benefits of running the test.


Running an A/B test is necessary if you want to be achieving the best results possible in your business. By following the guidelines put forward in this post, it’s clear that you need to take individual factors into consideration when deciding how long to run a test for. If you do this, then you can make the most of the benefits A/B testing provides.