Free OnlineCalculators & Converters
Standard Deviation Calculator
Calculate standard deviation, variance, mean, and other statistics for any dataset. Supports both population (÷N) and sample (÷N−1) formulas.
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Population or Sample?
Key Features — Standard Deviation Calculator
Population and sample standard deviation
Variance (σ² and s²)
Mean, min, max, range
Accepts comma or line-separated input
Up to millions of values
Why Use This Tool — Standard Deviation Calculator
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Frequently Asked Questions — Standard Deviation Calculator
What is standard deviation?
Standard deviation measures how spread out values are around the mean. A small standard deviation means values are clustered close to the mean; a large one means they are spread out widely. It is the square root of the variance.
When do I use population vs. sample standard deviation?
Use population standard deviation (σ, divides by N) when you have data for every member of the group. Use sample standard deviation (s, divides by N−1) when your data is a subset of a larger population — the N−1 denominator (Bessel's correction) gives an unbiased estimate of the population variance.
What is a good standard deviation?
There is no universal "good" standard deviation — it depends on context. In finance, lower is less volatile (less risky). In manufacturing, a tight (low) standard deviation means consistent quality. The coefficient of variation (CV = σ/mean) is often more useful than raw standard deviation for comparing datasets with different means.