Z-Score Calculator - Standard Score Calculator
Calculate z-scores to determine how many standard deviations a value is from the mean. Includes percentile conversion and interpretation.
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Enter the full dataset to calculate mean and std dev
A z-score (or standard score) indicates how many standard deviations a value is from the mean. Formula: z = (x - μ) / σ
- z = 0: Value is at the mean
- z > 0: Value is above the mean
- z < 0: Value is below the mean
- |z| < 1: Within 1 std dev (~68% of data)
- |z| < 2: Within 2 std dev (~95% of data)
- |z| < 3: Within 3 std dev (~99.7% of data)
- |z| > 3: Potential outlier
Z-scores are used in standardized testing, quality control, comparing values from different datasets, and identifying outliers.
How to Use Z-Score Calculator
- 1
Enter your dataset (comma, space, or newline separated).
- 2
Enter the value you want to calculate the z-score for.
- 3
Click "Calculate Z-Score" to get the result.
- 4
View z-score, percentile, mean, and standard deviation.
Frequently Asked Questions
What is a z-score?▾
A z-score (or standard score) indicates how many standard deviations a value is from the mean. Formula: z = (x - μ) / σ
How do I interpret z-scores?▾
z = 0 means the value is at the mean. Positive z-scores are above the mean, negative are below. |z| > 2 indicates an unusual value, |z| > 3 may be an outlier.
What are z-scores used for?▾
Z-scores are used in standardized testing, quality control, comparing values from different datasets, and identifying outliers.
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