P-Value Calculator
Find the p-value from a z-score, t-score, chi-square or F statistic.
Change the values and press Calculate to work out your own figures.
From a z-score
Enter a z-score.
Show the working
- Left tail = Φ(z) = 0.9772498681
- Two-tailed p = 2 × (1 − Φ(|z|)) = 0.0455002639
From a t-score
Enter a t-score and its degrees of freedom.
Show the working
- P(T < t) = 0.9749941141
- two-tailed p = 2 × min(left, right) = 0.05001177182
From a chi-square value
Enter a chi-square value and its degrees of freedom.
Show the working
- p = P(χ² > 3.84) = 0.05004352125
From an F value
Enter an F value and its two degrees of freedom.
Show the working
- p = P(F > 4) = 0.02207699966
How to use it
Enter a z-score. Enter a t-score and its degrees of freedom. Enter a chi-square value and its degrees of freedom. Enter an F value and its two degrees of freedom.
Probabilities can be typed as decimals, fractions or percentages. Show the working gives the formula with your numbers in it.
Key facts
two-tailed p = 2 × P(Z > |z|)
Reading a p-value
A p-value is the chance of a result at least this extreme if the null hypothesis were true. A small p-value (commonly below 0.05) is evidence against the null hypothesis; it is not the probability that the hypothesis is true.
Questions
What is the p-value for z = 2?
Two-tailed, 0.04550026390.
One-tailed or two-tailed?
Two-tailed unless the test only looks for a difference in one direction.
Formulas
two-tailed p = 2 × P(Z > |z|)
Sources
Limitations
- Probabilities can be typed as decimals (0.25), fractions (1/4) or percentages (25%).