Z-Score Calculator
z-score
+2
between 2σ and 3σ — uncommon
P(X ≤ x)
97.72%
Percentile: 97.7
P(X ≥ x)
2.28%
Two-tailed: 4.55%
z = (x − μ) / σ = (85 − 75) / 5 = 2
Probabilities use the standard normal CDF (Φ) via the Abramowitz–Stegun rational approximation — accurate to ~7 decimal places.
Probabilities use the standard normal CDF (Φ) via the Abramowitz–Stegun rational approximation — accurate to ~7 decimal places.