Standard Deviation Calculator — Sample & Population σ Guide

Calculators · Free guide
Standard deviation statistics calculator — illustration

Calculate standard deviation and variance from any data set — population or sample. Paste comma-separated numbers and read mean, σ or s, variance, and count for statistics homework, QC, and research. The TetraKits Standard Deviation Calculator runs entirely in your browser — free, private, and ready on mobile or desktop.

Overview

Quality control charts, survey analysis, and statistics coursework all need standard deviation — not just averages. Paste a data set, pick population or sample mode, and read σ, variance, and mean together.

How to use the standard deviation calculator

  1. Enter your data — Paste numbers separated by commas, spaces, or line breaks. Example: 12, 15, 14, 18, 16, 13.
  2. Choose population or sample — Use sample (n−1 denominator) when data is a subset of a larger group. Use population (n denominator) for the complete data set.
  3. Read σ, variance, and mean — See standard deviation, variance, mean, and count. For central tendency only, use the average calculator.

Common use cases

  • Enter your data: Paste numbers separated by commas, spaces, or line breaks.
  • Choose population or sample: Use sample (n−1 denominator) when data is a subset of a larger group.
  • Read σ, variance, and mean: See standard deviation, variance, mean, and count.
  • Bookmark for quick access: Save the tool for repeat tasks without installing an app.

Frequently asked questions

What is the difference between sample and population standard deviation?

Population (σ) divides by n — use when you have the entire data set. Sample (s) divides by n−1 — use when data is a sample of a larger population.

How is standard deviation calculated?

SD = √(Σ(x − mean)² / n) for population, or divide by n−1 for sample. It measures spread around the mean.

What is variance?

Variance is SD squared (σ²). Standard deviation is in the same units as your data — easier to interpret.

How many data points do I need?

At least two values for sample SD. More data points produce more stable estimates.

Is this standard deviation calculator free?

Yes. Unlimited data sets with no signup.