A/B Test Significance Calculator

Paste in the numbers from your test and find out whether the difference is real or just noise. Two-proportion z-test, computed live in your browser.

Control (A)

Variant (B)

Result
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Confidence toward significance —
Rate A
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Rate B
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Relative uplift
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Confidence
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p-value
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z-score
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How to read this

This runs a two-proportion z-test, the standard check for whether two conversion rates differ by more than chance. "Significant at 95%" means that if the variant truly made no difference, you would see a gap this large only about 5% of the time. It does not mean there is a 95% chance the variant is better, and it does not tell you the effect is large or durable.

A result can be significant and still not worth shipping, and a real effect can look flat if the test lacks the traffic to detect it. Decide your sample size before you start with the sample size calculator, and read the full method, including power, peeking, and business cycles, in statistical significance for product managers and the A/B testing program guide.

Built by Deepanshu Grover, a Growth Product Manager and AI builder in Paris. Runs entirely in your browser, nothing is sent anywhere. About · Get in touch