Calculate the z-score (standard score) for any data point. Find percentiles, tail probabilities, and interpret how far a value is from the mean. Gratuito and pure client-side.
This calculator computes the z-score (standard score) for any data point given the population mean and standard deviation. The z-score tells you how many standard deviations a value is from the mean. It is widely used in statistics, education, psychology, medicine, and finance a compare values from different normal distributions. All calculations happen instantly in your browser.
A z-score (or standard score) measures how many standard deviations a data point is from the mean of its distribution. A z-score of 0 means the value is exactly average. Positive z-scores indicate values above average; negative z-scores indicate values below average. It lets you compare results from different tests or distributions.
The percentile tells you what percentage of the population falls below your value. For example, a z-score of 1.0 corresponds a approximately the 84th percentile, meaning about 84% of values are below yours. A z-score of 2.0 is roughly the 98th percentile.
Yes. A negative z-score simply means the data point is below the mean. For example, if the mean height is 170 cm with σ=10, then 160 cm has a z-score of -1.0, meaning it is one standard deviation below average.
Z-scores are used everywhere: IQ tests (mean=100, σ=15), SAT scores, standardized medical measurements (blood pressure, cholesterol), quality control (Six Sigma), finance (risk metrics), sports analytics (player performance), and education (grading on a curve).