Standard Score (Z-Score) Calculator 2025
Convert any score into a standardized value and see where it falls on the bell curve.
Derived Standard Scores
Z-Score
0.00
Percentile
0
Score on the Normal Distribution
Standard Score FAQ
What is a Standard Score (Z-Score)?
A Z-score measures how many standard deviations a data point is from the mean of a dataset. A Z-score of 0 means the data point is exactly average. A positive Z-score means it's above average, and a negative Z-score means it's below average. It's a universal way to compare values from different datasets (e.g., comparing your height to the average height vs. your test score to the average test score).
What is a Percentile?
A percentile indicates the percentage of scores in a dataset that are at or below a particular score. For example, if your score is in the 84th percentile, it means you scored higher than or equal to 84% of the people in the comparison group.
What are T-Scores and other derived scores?
These are transformations of the Z-score to make them easier to interpret by removing decimals and negative numbers. They all represent the same underlying position on the bell curve.
- T-Score: Sets the mean to 50 and standard deviation to 10. Formula:
Z * 10 + 50
. - IQ Score (Wechsler Scale): Sets the mean to 100 and standard deviation to 15. Formula:
Z * 15 + 100
. - SAT Score: Each section has an approximate mean of 500 and standard deviation of 100. Formula:
Z * 100 + 500
.