P-value Calculator — from z, t, or Chi-Square
Use this free p-value calculator to convert a z, t, or chi-square test statistic into a p-value. Choose one-tailed or two-tailed, and see whether the result is significant at the 0.05 level, with step-by-step working.
What the p-value means
The p-value is the probability of getting a test statistic at least as extreme as yours if the null hypothesis were true. A small p-value (typically below 0.05) is evidence against the null hypothesis.
How to use it
- Pick the distribution (z, t, or χ²) and the tail.
- Enter the statistic (and degrees of freedom for t and χ²).
- Press Find p-value.
Related: the Z-Score Calculator and more free math calculators.
Frequently asked questions
One-tailed or two-tailed?
Use two-tailed when the alternative is simply ‘different’; use one-tailed when it specifies a direction (greater or less).
Which distributions are supported?
Standard normal (z), Student’s t (with degrees of freedom), and chi-square (with degrees of freedom).
What counts as significant?
By the common convention, p < 0.05; the calculator flags this for you.
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