Turn a test statistic into the p-value you need to accept or reject a hypothesis. Enter a z score and choose a left tailed, right tailed, or two tailed test, and the tool returns the p-value along with whether it clears the common 0.05 threshold. The p-value is the probability of seeing a result at least as extreme as yours if the null hypothesis were true, computed here from the normal cumulative distribution function. A small p-value, typically under 0.05, is the usual signal that an effect is unlikely to be due to chance alone. This is the final step of a z test after you have standardized your statistic. It is used across science, A/B testing, and quality analysis. Everything is calculated locally in your browser, so your data stays private on your device.
It is the probability of seeing a result at least as extreme as your z-score if the null hypothesis were true.
A one-tailed test checks one direction while a two-tailed test checks both, so the two-tailed p-value is doubled.
A p-value below your chosen threshold, often 0.05, suggests the result is statistically significant.
Turn a test statistic into the p-value you need to accept or reject a hypothesis. Enter a z score and choose a left tailed, right tailed, or two tailed test, and the tool returns the p-value along with whether it clears the common 0.
Yes. P-Value from Z-Score Calculator is completely free, with no sign-up and no usage limits.
Yes. P-Value from Z-Score Calculator runs in any modern web browser. There is nothing to download or install.
Yes. P-Value from Z-Score Calculator runs entirely on your device in your browser, so nothing you enter is uploaded to a server.