🛠️ Tool
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Free
Beginner
Why we picked it When one ad beats another, this free calculator tells you whether the gap is real or just luck. You plug in visitors and conversions for each version and it returns the probability that the difference holds up, no spreadsheet or stats background needed. Use it as a gut check before you shift budget onto the ad that only looks like the winner.
A/B Test Statistical Significance Calculator
From VWO by VWO
- Enter visitors and conversions for control and variant, and it reports the chance the difference is genuine rather than noise.
- A small lead on small numbers usually comes back as not significant, which is the honest answer you want before spending more.
- It is free and needs no signup, so you can sanity-check every head-to-head test as you run it.