Como usar: A/B Test Significance Calculator
- Enter the visitors and conversions for version A, your control.
- Enter the same for version B.
- Pick a confidence level. 95% is the usual choice.
- Read the result, then check the p-value and the range of the difference.
What statistical significance means
Random variation means two identical pages rarely show identical rates. A significance test asks how likely a difference this large would be if the versions performed the same. That chance is the p-value. At 95% confidence, a result counts as significant when the p-value is below 0.05.
How it’s calculated
This tool uses a two-sided, two-proportion z-test. The formula is z = (rate B − rate A) ÷ √(p(1 − p)(1/visitors A + 1/visitors B)), where p is the combined conversion rate.
Avoid common mistakes
- Don’t stop early. Checking daily and stopping at the first significant result produces false winners.
- Plan your sample. Use the A/B Test Sample Size Calculator before you start.
- Run full weeks. Weekday and weekend visitors behave differently.
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Ferramentas que combinam com: A/B Test Significance Calculator
- CTR Calculator — Enter clicks and impressions to get your click-through rate, for ads, email or Search Console.
- ROAS Calculator — See what each ad dollar brings back.
- UTM Builder — Add utm_source, utm_medium, utm_campaign and friends to any link, see which GA4 channel the visit will land in, and tag a whole list of URLs at once.
- Calculadora de porcentagem — Sete cálculos de porcentagem do dia a dia em uma única página.
Perguntas frequentes
Is anything I enter saved or sent?
No. The calculation runs in your browser. Your last inputs are remembered on this device only, so the page opens where you left off.
What p-value is good for an A/B test?
Below 0.05 is the usual standard, which matches 95% confidence. Use 0.01 for high-stakes changes.
Is 95% confidence the chance that B is better?
Not exactly. It means that if there were no real difference, a result this extreme would appear less than 5% of the time.
Why is my result not significant?
Usually the sample is too small for the size of the difference. Keep the test running to your planned sample size.
Posso instalar o A/B Test Significance Calculator como um aplicativo da web e usá-lo offline?
Sim. O A/B Test Significance Calculator é um aplicativo da web instalável (PWA) — instalado a partir do seu navegador, não baixado de uma loja de aplicativos. Clique em “Instalar aplicativo” na parte superior desta página no Chrome ou no Edge (Windows, macOS, Linux, ChromeOS) ou, no Android, use “Compartilhar” → “Adicionar à tela inicial” no iPhone e no iPad, ou “Arquivo” → “Adicionar ao Dock” no Safari 17+ em um Mac. Em seguida, ela se abre em uma janela própria com seu próprio ícone e, como é executada inteiramente no seu navegador, continua funcionando offline. O Firefox no desktop não permite a instalação de aplicativos da web. Como funciona a instalação.