Method
Left tail = Φ(z), right tail = 1−Φ(z), and two-sided p = 2×min(left,right) under the standard-normal null model.
Math worksheet
Z-Test P-Value Calculator
Convert a standard-normal test statistic into left-, right- or two-sided p-values and compare the result with a prespecified alpha level.
The calculation runs locally. Exact-integer tools avoid floating point; decimal and transcendental tools report rounding limits.
Method and verification guide
How the Z-Test P-Value Calculator works
Left tail = Φ(z), right tail = 1−Φ(z), and two-sided p = 2×min(left,right) under the standard-normal null model. The calculator keeps the intermediate values visible so you can reproduce the answer independently.
Interpret the result
The p-value is the probability, under the specified null model, of a result at least as incompatible in the selected direction.
Check the assumptions
A p-value is not the probability that the null hypothesis is true and does not measure effect size or practical importance.
Local calculation
Everything runs in this browser. Inputs are not sent to an external calculator.
Rounding
Displayed values may be rounded for readability while calculations use full floating-point precision unless the tool explicitly uses exact integers.
Scope
A p-value is not the probability that the null hypothesis is true and does not measure effect size or practical importance.
Simple by design
Three steps to a clearer number.
Enter your details
Use realistic values in each field. You can change them anytime.
Calculate instantly
The formula runs locally, so there is no account or waiting time.
Use the result
Treat the answer as a practical estimate for your next decision.