P-Value Calculator
P-value from a z, t, chi-square, or F statistic for any tail.
About this tool
Choose the distribution, enter the test statistic, df where needed and the tail. The p-value is the probability of a result at least as extreme under the null hypothesis.
How to use
How it works
A small p-value means the data are unlikely under the null hypothesis. Compare it with your alpha, usually 0.05. A p-value is not the probability that the null is true. Use the tail that matches your alternative hypothesis.
two-tailed p = 2 × P(|T| ≥ |t|) right-tailed p = P(T ≥ t)
Worked example
A t statistic of 2.086
- Input
- t, df = 20, statistic = 2.086, two-tailed
- Output
- p = 0.049996
- Walkthrough
- 2.086 is the 0.05 two-tailed cut-off for 20 df, so p lands at 0.05. For z = 2.33 right-tailed p = 0.009903.
Limitations
- You must choose the distribution and tail yourself.
- A p-value alone does not give effect size.
Questions
What p-value is z = 2.33?
What p-value is chi-square 9.488 with df 4?
Is p < 0.05 significant?
Features
- Four distributions
- Any tail
- Runs in your browser
Guides
Related resources
Guides and videos from around the web—opens on YouTube or the publisher’s site.
Student's t-distribution
Khan Academy
Why t-tables differ from z for small samples.
Watch on YouTubeHypothesis testing and p-values
StatQuest with Josh Starmer
Intuition for t/z/χ² decision rules.
Watch on YouTube
- Statistics and probability
Khan Academy
Full intro stats path next to hub calculators.
- Chi-squared distribution
Wikipedia
Reference for χ² critical values and tests.