A/B Test Significance Calculator
Determine if your A/B test results are statistically significant.
Enter visitors and conversions for both variants.
A/B Test Results
Statistical significance tells you whether the difference between two variants is real or due to random chance.
Conversion Rate = Conversions / Visitors
The calculator uses a Z-test for two proportions:
Z = (p1 - p2) / sqrt(p_pool × (1 - p_pool) × (1/n1 + 1/n2))
Where p_pool = (conversions_A + conversions_B) / (visitors_A + visitors_B)
Confidence levels:
- 90% — Z > 1.645 (weak evidence)
- 95% — Z > 1.96 (standard threshold)
- 99% — Z > 2.576 (strong evidence)
Best practices:
- Run tests for at least 1–2 full business cycles (typically 2 weeks)
- Aim for at least 1,000 visitors per variant
- Do not stop tests early when you see significance