Free Tool

Statistical Significance Calculator

To determine statistical significance, run a two-proportion z-test: z = (pB − pA) / SE, then convert z to a p-value. If the p-value is below 0.05, the result is significant. This free statistical significance calculator does it for you — enter control and variant visitors and conversions to get the p-value, z-score and confidence level instantly.

Example: Control 350/10,000 (3.50%) vs. Variant 410/10,000 (4.10%) gives z ≈ 2.18, p ≈ 0.029 — significant at 95% confidence.

Z-Test Calculator Enter data to calculate

Enter the visitor and conversion counts for each variant from your testing platform.

Control (A)

Variant (B)

The threshold below which you'll reject the null hypothesis.

Enter your control and variant data to check statistical significance.

Understanding statistical significance

Statistical significance tells you the probability that the difference between your control and variant happened by chance. A p-value below 0.05 means there's less than a 5% chance the difference is random – it's likely real. For a deeper walkthrough of why 95% is the standard and the mistakes that cause false positives, read A/B testing statistical significance explained.

Significance only answers whether a difference is real – not whether you've collected enough data to detect it. Before you launch a test, use our sample size calculator to find the visitors you need, and our A/B test calculator for a full results breakdown.

Key concepts

P-value

The probability of observing your results (or more extreme) if there's actually no difference between A and B. Lower p-value = stronger evidence of a real effect.

Z-score

How many standard deviations your observed difference is from zero. A z-score above 1.96 (or below -1.96) is significant at the 95% level for two-tailed tests.

One-tailed vs. two-tailed

Two-tailed tests check if B is different from A (either direction). One-tailed tests only check if B is better. Use two-tailed unless you have a strong directional hypothesis.

Need help interpreting your test results?

Statistical significance is just the starting point. Our CRO team will tell you whether to ship, iterate, or pivot – and what to test next.

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Go deeper
A/B TestingA/B Testing Statistical Significance ExplainedWhat statistical significance actually means in A/B testing, why 95% is the standard, and the mistakes that lead to false positives and premature test calls.