Standard Score (Z-Score) Calculator 2025

Convert any score into a standardized value and see where it falls on the bell curve.

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Derived Standard Scores

T-Score: 0
IQ Score (Wechsler): 0
SAT Score (approx.): 0
ACT Score (approx.): 0

Z-Score

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Percentile

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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.