Standardize a value against a mean and standard deviation, or convert a z-score back to a raw value.
A z-score is how many standard deviations a value sits from the mean. A z of 0 means the value equals the mean; positive means above it, negative means below it — e.g. z = 1.5 means the value is 1.5 standard deviations above the mean.
It's the area under the standard normal curve to the left of your z-score, computed from the normal cumulative distribution function. A percentile of 84% means roughly 84% of a normally distributed population falls below that value.
It reverses the standard formula: x = z × σ + μ. Instead of standardizing a raw value, you enter a target z-score plus the mean and standard deviation, and the calculator solves for the raw value that would produce that z-score.