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Sample size calculator for A/B testing

Sample size & test length calculator

Monthly unique visitors The number of unique visitors that will be included in your test.
Variations plus original Total number of variations including original that is included in the test.
Baseline conversion rate (%) The avarage conversion rate of visitors that will be part of the test. Generally found in Google Analytics.
Minimal detectable effect (%) The miminum increase in the baseline conversion rate that you are looking to detect.

Significance (%)
The probability that the result is not a false positive. Default is 90.
Power (%)
The probability that the result is not a false negative. Default is 80.
Sample size per variation

Total sample size

Estimated time

How we calculate

This calculator is used to compute the sample size for your variations and the test length and is based on the SiteGainer Stats Engine which employees the Frequentist methodology known as a one-tailed Z test for the difference between two proportions.

When testing one or more variations, the calculator adjusts the sample size using the Bonferroni correction.

For more information on why we are using one-tail tests, read Common misconceptions about one-tailed vs. two-tailed tests

Need assistance?

Please use our chat or e-mail to get assistance on how to determine your sample size.