Z-Score Calculators

This page has two interactive Z-score calculators. The first calculator computes a Z-score based on your observed value, the mean, and the standard deviation. The second uses a Z-score to find the probability of various ranges under the standard normal distribution. See all my Statistical Calculators!

Use the first Z-score calculator when you want to standardize a data point—that is, convert an observed value to a Z-score using the formula:

To use the calculator:

Enter your observed value (x) — the raw data point you want to standardize.
Enter the mean (μ) — the average of the population or sample.
Enter the standard deviation (σ) — how spread out the values are.

Click Calculate Z-score to see the standardized result. A graph below the output shows the Z-score’s location on the normal curve and shades the area to the left.

Z-Score Calculator

Observed value (x)

Mean (μ)

Standard deviation (σ)

The following Z-score calculator takes a Z-score and calculates the probability associated with different regions of the standard normal distribution relative to your Z-score.

To use the calculator:

Enter your Z-score.
Click Calculate to view the probabilities.

A small graph highlighting the shaded region of interest under the bell curve shows which area corresponds to each probability.

Z-Score Probability Calculator with Graphs

Enter Z-score:

P(Z < z):

P(Z > z):

P(0 < Z < z):

P(-z < Z < z):

P(Z < -z or Z > z):

Z-Score Calculators