Free tool

A/B Test Significance Calculator

Enter each variant's numbers and find out whether the difference is real or just noise — statistical confidence, uplift and a plain-English verdict. Two-proportion z-test, in your browser.

Metric
Confidence level

Variant A

Rate: 5.00%

Variant B

Rate: 6.50%

Not significant yet at 95%

85.0% confidence · p = 0.1496

Rate A

5.00%

Rate B

6.50%

Relative uplift

+30.0%

Confidence

85.0%

The difference could still be random noise. There's a 15.0% chance you'd see this gap even if the variants were truly equal — keep the test running to gather more data, or the true effect may just be too small to matter.

Two-proportion z-test (two-tailed). Significance ≠ business impact — a tiny but “significant” lift on huge traffic may not be worth shipping. Avoid peeking and stopping the moment it goes green.