A/B Test Statistical Significance Calculator
Check whether your A/B test winner is real or just random noise.
Variant A (control)
Variant B (test)
Rate A
5.00%
210 / 4,200
Rate B
6.27%
262 / 4,180
Relative uplift
25.4%
B vs A
Confidence
98.8%
Chance the result is real
Significant at 98.8% confidence (≥95%). Variant B's 25.4% uplift is very unlikely to be noise — safe to ship.
Two-proportion z-test for a single comparison. It doesn't correct for peeking or multiple variants — decide your sample size before you start, not after you like the number.
About this calculator
Enter visitors and conversions for each variant to get conversion rates, uplift and the statistical confidence that the difference is real — so you stop shipping losers.
Everything runs in your browser — nothing you type is sent anywhere or stored. Use it to sanity-check a plan, pressure-test a channel, or brief a team before you commit budget.