Quick answer: An A/B significance calculator tells you whether the difference between two variants is real or just chance. Enter each variant’s visitors and conversions; it runs a two-proportion z-test and reports the confidence level and whether the result is statistically significant (usually at 95%).
A/B test significance calculator
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Conversion rate A
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Conversion rate B
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Relative uplift (B vs A)
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Confidence
Run A/B tests on subject lines, sends and flows inside Bluey Email — built-in on every plan with send-based pricing. See how.
How significance is calculated
This tool uses a two-proportion z-test. It computes each variant’s conversion rate, pools them to estimate the standard error, and derives a z-score and two-tailed p-value. Confidence = 1 − p-value. If confidence meets your threshold (95% by default), the difference is unlikely to be random. Significance is not the whole story — make sure you have enough sample size and run the test for full business cycles before calling a winner.
Frequently asked questions
What does statistical significance mean?It means the observed difference is unlikely to be due to chance. At 95% confidence, there is roughly a 5% probability the result is a fluke.
What confidence level should I use?95% is the standard for marketing tests. Use 99% when the decision is high-stakes, or 90% for quick directional reads.
Why is my result not significant?Usually too small a sample or too small a difference. Collect more data or wait for a larger effect before deciding.
Is this calculator free?Yes — free and private, computed in your browser.