Formula and calculation method
Right-tailed p = 1−Φ(z). Left-tailed p = Φ(z). Two-sided p = 2[1−Φ(|z|)].
Standard normal z test only. A p value is not the probability that the null hypothesis is true; t, chi-square and F tests need other distributions.
How to use p-value calculator
- Set Observed z statistic. The example below uses 1.96.
- Set Alternative hypothesis by choosing the option that matches your calculation.
- Select Calculate to update the result. Reset restores the illustrated inputs. Copy, print or download your own result if you need a record.
Worked example
Example inputs
- Observed z statistic
- 1.96
- Alternative hypothesis
- Two-sided
- P value
- 0.04999579
Factors affecting your result
Standard normal z test only. A p value is not the probability that the null hypothesis is true; t, chi-square and F tests need other distributions.
Changing observed z statistic changes the scenario being evaluated. Adjust one input at a time when comparing results, keep a copy of the assumptions, and compare values using the same unit and period. A precise arithmetic result does not make an uncertain assumption precise.
Frequently asked questions
How does the p-value calculator work?
Right-tailed p = 1−Φ(z). Left-tailed p = Φ(z). Two-sided p = 2[1−Φ(|z|)].
What inputs does P-Value Calculator need?
Enter observed z statistic, alternative hypothesis. Choose values that correspond to the same situation and measurement convention.
How should I interpret the p-value calculator result?
Standard normal z test only. A p value is not the probability that the null hypothesis is true; t, chi-square and F tests need other distributions.
Are my p-value calculator inputs uploaded?
No. The calculation runs in this browser. Favorites, recent tool names, theme and formatting preferences may be saved locally, but calculation inputs are not sent to a calculation server or stored by this website. Shared links do not include entered values.
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