What is a good z-score?

A z-score of 1.0 or higher means you are above average. A z-score of 2.0+ means you are in roughly the top 2.5% of the class.

Can a z-score be negative?

Yes, a negative z-score means your score is below the class average.

A z-score of 0 is the 50th percentile, 1.0 is about the 84th percentile, and 2.0 is about the 97.7th percentile.

Calculate the z-score for a test grade given the class mean and standard deviation. Understand how far your score is from the average.

Your Score

Class Mean

Standard Deviation

Z-Score

1.00

Points Above Mean10.0

Standard Deviations from Mean1.00

Z-Score vs Your Score

A z-score measures how many standard deviations a score is from the mean.

Z = (Score - Mean) / Standard Deviation

Z = 0 means you scored at the average

Z > 0 means above average

Z < 0 means below average

A student scores 85 in a class with mean 75 and standard deviation 10.

Calculate standard scores.

Find your percentile rank.

See how grading on a curve works.