P-value Calculator
Convert z, t, chi-square, F and r statistics into p-values.
Enter your values to see the result.
Chi-square and F tests are right-tailed by definition. A p-value is not the probability that the null hypothesis is true; report effect sizes and confidence intervals alongside it.
Continue your work
- Effect Size Calculator — Turn test statistics into effect sizes.
- 2×2 Contingency Table Calculator — Run a chi-square test from counts.
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Clear instructions
Find steps, examples and limitations below.
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How to use the P-value Calculator
Convert z, t, chi-square, F and r statistics into p-values.
- 1 Choose the test statistic you have.
- 2 Enter its value and the degrees of freedom or sample size.
- 3 Choose one or two tails and read the p-value.
Example and practical tips
t = 2.1 with 24 degrees of freedom gives a two-tailed p-value of 0.046, significant at α = 0.05.
Frequently asked questions
One-tailed or two-tailed?
Use two-tailed unless you decided before seeing the data that only one direction matters. A one-tailed p is half the two-tailed value.
Does p < 0.05 mean the effect is important?
No. It only suggests the data are unlikely under the null hypothesis. Check the effect size and confidence interval for importance.
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