Calculate the z-score (standard score) for a value given the population mean and standard deviation, along with its percentile rank.
A z-score measures how many standard deviations a data point is from the mean of its distribution.
Z equals x minus the mean, divided by the standard deviation. The percentile is derived from the standard normal cumulative distribution function.
Enter the value, the mean, and the standard deviation of the data set, then click Calculate to see the z-score and percentile.
Example: A test score of 85 with a mean of 75 and standard deviation of 10 gives a z-score of 1.0, meaning it is one standard deviation above average.
What does a negative z-score mean. It means the value is below the mean of the distribution.
What is a typical z-score range. Most values in a normal distribution fall between negative 3 and positive 3.