Free calculator
A/B test significance calculator
Two-tailed two-proportion z-test with pooled variance. Punch in your visitors and conversions; get confidence, lift, and a plain-English verdict.
Confidence
94.17%
Control rate5.00%
Variant rate5.60%
Relative lift+12.00%
p-value0.0583
z-score1.894
Verdict
⏳ Not significant yet. Keep running or accept flat.
How to read the result
- Confidence ≥ 95% — safe to ship the winner. This is the industry-standard cutoff and what most CRO tools default to.
- Confidence < 95% — keep running, or accept the result as flat. A lower confidence bound trades ship velocity for false-positive risk.
- Lift is relative to the control. +10% lift on a 5% baseline means the variant converts at 5.5%.
- Runs are noisy in the first few days. Small samples produce confident-looking p-values that flip once volume arrives. Estimate the sample size you need before you start.
Related
- Sample-size calculator → How many visitors per variant you need.
- Test-duration calculator → How many days a test needs to run at your traffic level.
- Glossary of A/B testing terms
- Live A/B tests from 1,000+ brands