Sample Size Calculator

Free statistical significance calculator

How many users do you need for a/b testing and how long should your tests run?

Our sample size calculator help you calculate the minimum sample size as well as the duration of your tests based on your audience, your conversions and other information such as the Minimum Detectable Effect. If you need more explanations, all indicators are explained in the FAQ below the calculator.

How many users do you need?

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[?] %
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Required number of tested visitors
per variation

How long should your test run?

Our statistical significance calculator also gives you an idea of the duration of your A/B test. For this A/B test duration calculator to work, please fill in the information above, as well as your average daily traffic on the tested page and your number of variations - including the control version.

You may also be interested in this more in-depth blog post where we discussed how long your A/B test should run.

Required duration in days

How to figure out the Minimum Detectable Effect?

If you have absolutely no clue how to choose this MDE, we've got you covered!


The goal is to provide a simple way to compute the needed amount of visitors required for a test to be statistically significant (e.g. the needed amount of visitors you need to assess that a lift/loss of x% can be trusted with 95% confidence).

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