How to use this calculator
Choose a conversion or paste numbers to standardize.
Formula and method
z = (x − μ)/σ; x = μ + zσ. Dataset SD uses n or n−1 as selected.
Worked example
85 with mean 70 and SD 10 gives z = 1.5 and normal percentile ≈ 93.319%.
Assumptions and supported scope
SD must be positive. Dataset values must vary; 2–500 observations. Normal percentiles require a normal model. CDF approximation error ≈ 7.5×10⁻⁸.
Method references
Method and worked example checked against the calculator implementation. About our methods · Report a correction