P-value Calculator
Convert a z-score into one- and two-tailed p-values under the standard normal distribution (z test).
Runs 100% in your browser — nothing is uploaded.
Result
Formula
Two-tailed p = 2·(1 − Φ(|z|)); upper one-tailed p = 1 − Φ(z); lower = Φ(z).
About this calculator
The p-value is the probability of a test statistic at least as extreme as yours under the null hypothesis. Small p-values (below α) are evidence against the null.
How to use
- 1
Enter your Z-score in the 'Z-score' field.
- 2
Choose the 'Direction' of your test: 'Two-tailed', 'Right tail', or 'Left tail'.
- 3
Set the 'Significance α' (in %) and read the P-value and significance conclusion.
Frequently asked questions
Do you support t, χ² and F tests?
This release covers the normal (z) distribution. t, chi-square and F distributions are planned.
Please note: Results are estimates for general information only and are not professional or medical/financial advice.