Did version B really win, or is it luck? Enter visitors and conversions for both versions of your page, ad or email.
Confidence that the difference is real
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Rate A
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Rate B
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Relative lift of B vs A
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Z-score
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p-value
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Below 0.05 = significant at 95%
Winner
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What is the A/B Test Significance Calculator?
Version B got more conversions — but is it really better, or just luck? This calculator tells you whether the difference between two versions of a page, ad or email is statistically significant.
Enter visitors and conversions for both versions to see the rates, the lift, the confidence level, the z-score and the p-value.
How to use the A/B Test Significance Calculator
- Enter visitors (or recipients) and conversions for version A.
- Do the same for version B.
- Wait for 95% confidence before declaring a winner.
Understanding your results
- Confidence
- How sure you can be that the difference is real. 95% is the usual threshold.
- p-value
- The probability of seeing this difference by chance. Below 0.05 = significant at 95%.
Frequently asked questions
What confidence level should I use?
95% is standard; 90% is acceptable for low-risk changes.
How long should I run an A/B test?
At least one full week to cover weekday patterns, and until you reach the sample size you planned.
Why isn’t my test significant?
The difference may be small or the sample too small. Use the sample size calculator before testing.