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About the Z-score Calculator
This calculator computes the z-score for any data point in a normal distribution. Enter a raw value, the mean, and the standard deviation, and you get the z-score, its percentile rank, and the probability of a value falling above or below it.
The tool applies the standard formula z = (x - μ) / σ, where x is your data point, μ is the population mean, and σ is the standard deviation. It then reads the matching percentile and probability from the standard normal distribution. Keep the raw value, mean, and standard deviation in the same units so the result stays meaningful. For small samples, use the sample standard deviation and treat the output as an estimate.
- Enter your raw data point in the value field.
- Type the population mean and standard deviation.
- Press calculate to see the z-score, percentile, and probabilities.