📐 Z-Score Calculator
Enter a raw value along with the mean and standard deviation of its data set to calculate the z-score (standard score).
What a z-score tells you
A z-score (or standard score) tells you how many standard deviations a value is above or below the mean of its data set. A z-score of 0 means the value equals the mean; positive means above average; negative means below average.
How this calculator works
The formula is z = (x – mean) / standard deviation, where x is your raw value. This calculator also converts that z-score into an approximate percentile using the standard normal distribution, assuming your data is roughly normally distributed (a common assumption for test scores, measurements, and similar data).
A z-score beyond about +/-2 is generally considered unusual, and beyond +/-3 is rare, in a normal distribution. This tool is intended for general educational purposes.