A/B Test Sample Size Calculator
Estimate visitors needed per variant for an A/B test with a simplified formula.
Quick answer: enter your details below and click Estimate Sample Size — your result appears instantly, right here in your browser. Nothing you enter is uploaded or stored.
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How to use
- Enter baseline conversion rate.
- Enter the relative uplift you want to detect.
- Click Estimate Sample Size.
About this tool
Enter baseline conversion, the relative uplift you want to detect, and the tool estimates visitors per variant using a simplified standard approximation. This is a rough planning estimate, not a substitute for a proper power calculation, so treat the result as a starting point and check it before running a high-stakes test.
Frequently asked questions
Is this estimate exact?
No. It is a simplified approximation for planning. A statistics tool or analyst should confirm sizes for important tests.
What if traffic is low?
Test bigger changes, or accept a longer run. Small uplifts on low traffic can take impractically long to prove.