Z-Score Calculator
Find how many standard deviations a value is from the mean.
How it works
z = (value − mean) ÷ standard deviation. Percentiles assume a normal (bell curve) distribution and use a numerical approximation of the normal CDF, accurate to roughly 6 decimal places. Example: with the default values, z-score comes to 1.5.
FAQ
Is this calculator free?
Yes. No signup is needed and nothing you enter is stored.
Is the result exact?
Results are rounded for display. For financial, medical, or legal decisions, confirm with a professional.
Do my numbers leave my device?
No. The calculation runs in your browser.