Standard Deviation Calculator
Calculate standard deviation, variance, mean, and other statistics for sample and population data. Free online standard deviation calculator.
Formulas
Mean: x̄ = Σx / n
Population Standard Deviation: σ = √(Σ(x - x̄)² / n)
Sample Standard Deviation: s = √(Σ(x - x̄)² / (n-1))
Variance: σ² or s² (square of std dev)
Standard Error: SE = s / √n
CV (%): CV = (σ / x̄) × 100%
Sample vs Population
Sample: Use when your data is a subset of a larger population. Divides by (n-1) to correct for bias.
Population: Use when your data includes the entire population. Divides by n.
In most real-world cases, use sample standard deviation.
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Last updated: January 2026