Percentile Calculator: run percentile calculations online. Formula, assumptions, and interpretation guide.
Z = (x − μ) / σ
Where x = observed value, μ = population mean, σ = standard deviation.
Percentile: use the standard normal cumulative distribution function Φ(Z) — a Z of +1.645 corresponds to the 95th percentile; Z of −1.96 corresponds to the 2.5th percentile.