Z-Score Calculator
Calculate Z-score, percentile, and probabilities for the standard normal distribution.
Formula
Z = (X - μ) / σ
Z-Score
-1.0000
Percentile
15.87%
Std. Dev. from Mean
1.00
Interpretation
Within 1 standard deviation (68% of data)
Probability Below
15.87%
Probability Above
84.13%
What is a Z-Score?
The Z-score measures how many standard deviations a value is from the mean. A Z-score of 0 means the value is exactly at the mean, while positive/negative values indicate how far above/below the mean.
Applications
Z-scores are used in standardized testing, quality control, financial analysis, and any field that requires comparing values from different distributions.
Empirical Rule
In a normal distribution: approximately 68% of data falls within 1 standard deviation, 95% within 2, and 99.7% within 3 standard deviations from the mean.