Calculate z-score (standard score) to find how many standard deviations a value is from the mean
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Z-score tells you exactly where a value falls in a normal distribution. Our calculator converts raw values to z-scores, finds percentiles, and calculates probabilities. Essential for standardized testing, statistics, and data analysis.
A z-score (or standard score) measures how many standard deviations a data point is from the mean. A z-score of 0 means the value equals the mean. Positive z-scores are above the mean, negative below. In a normal distribution, about 68% of values have z-scores between -1 and +1, and 95% between -2 and +2.
Z-Score Formula
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A z-score of 1.96 means the value is 1.96 standard deviations above the mean. In a normal distribution, about 97.5% of values fall below this point, making it the 97.5th percentile. This is why ±1.96 defines the 95% confidence interval.