A/B Test Sample Size Calculator

Stop guessing when to end your test. Calculate the exact traffic you need for statistically valid results.

Calculate the required sample size for statistically significant A/B test results.

Current Conversion Rate: 3%

Minimum Detectable Effect (relative): 20%

Detect a change from 3% to 3.60% conversion rate

Significance Level

Statistical Power

Variations

Daily Visitors (optional)

Per Variation

13,915

visitors needed

Total Sample Size

27,830

across 2 variations

Formula reference

n = (Z_α/2 + Z_β)² × [p₁(1-p₁) + p₂(1-p₂)] / (p₁ - p₂)²

Running A/B tests on broken tracking?

Your test results are only as good as your data. If GA4 is missing conversions, your winning variant might actually be losing.