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.
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.
The probability that the result is not a false negative. Default is 80.
Sample size per variation
Total sample size
Estimated time
days
Total sample size
Estimated time
days
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 support@symplify.com to get assistance on how to determine your sample size.