Free tool
A/B test sample size calculator
Plan how much traffic you need before you launch. Enter your baseline conversion rate and the smallest lift you care about, then pick your confidence and power targets.
Estimated visitors per variant
19,718
About 39,436 total visitors for a 50/50 A/B test detecting a move from 3% to 3.50%.
Uses a standard two-proportion z-test power calculation. Rounded up to whole visitors. Actual runtime depends on traffic to the page you are testing.
RunPivot monitors live experiments and calls winners at statistical significance. Start with RunPivot or explore live results in the product.