Population vs sample
Population SD uses the full dataset (divides by n). Sample SD estimates the population from a subset (divides by n-1, Bessel's correction).
Statistics tools
Standard Deviation Calculator
Calculate mean, standard deviation, variance, and more from a number list.
Complete guide
How to use Standard Deviation Calculator
Paste or type a list of numbers separated by commas or new lines. The calculator returns count, sum, mean, median, mode, standard deviation, variance, min, and max.
Choose Population (σ) if your data represents the entire group, or Sample (s) if it represents a subset. Sample standard deviation divides by n-1 (Bessel's correction).
What standard deviation tells you
Low SD means values cluster near the mean. High SD means values are spread out. Useful for measuring consistency, risk, and variability.
When to use each stat
Mean for average. Median when there are outliers. Mode for most common value. SD for spread. Variance for further statistical calculations.
Answers
Standard Deviation Calculator FAQs
What is standard deviation?
A measure of how spread out numbers are around the mean. Low SD means values are close together; high SD means they are spread apart.
What is the difference between population and sample standard deviation?
Population SD divides by n (the full count). Sample SD divides by n-1 to correct for using a subset of data.
How do I calculate standard deviation?
Find the mean, subtract it from each value, square each difference, average the squares, then take the square root.
What does a high standard deviation mean?
Data points are spread far from the mean — high variability in the dataset.
What is variance?
Variance is the square of standard deviation. It quantifies the average squared deviation from the mean.
Related tools