Free OnlineCalculators & Converters
Z-Score Calculator
Calculate z-scores and find probabilities for normal distributions. Convert raw scores to z-scores or find the probability area under the curve.
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Key Features — Z-Score Calculator
Z-score from raw value, mean, and standard deviation
Probability below, above, and within z
Find probability from z-score
Standard normal CDF calculation
Common critical values reference
Why Use This Tool — Z-Score Calculator
Free Online Z score calculatorZ-score calculator — for EveryoneFast & Easy Standard score calculatorNormal distribution z score — 100% FreeFree Online Z score to probabilityCalculate z score — for Everyone
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Frequently Asked Questions — Z-Score Calculator
What is a z-score?
A z-score (standard score) tells you how many standard deviations a value is above or below the mean. Z = (X − μ) / σ. A z-score of 0 means the value equals the mean. Z = 1 means one standard deviation above the mean. Z = −2 means two standard deviations below.
What does a z-score of 1.96 mean?
A z-score of 1.96 is the critical value for a 95% confidence interval. It means the value is 1.96 standard deviations above the mean. In a normal distribution, 95% of data falls within ±1.96 standard deviations of the mean, leaving 2.5% in each tail.
How do I interpret a negative z-score?
A negative z-score means the value is below the mean. For example, z = −1.5 means the value is 1.5 standard deviations below the mean. The probability of being below this value is the same as the probability of being above z = +1.5.