Math & Scientific
Standard Deviation Calculator
Standard Deviation — it computes the standard deviation as √(Σ(x − mean)² ÷ n) for a population, or ÷ (n − 1) for a sample. This page runs that same calculation on your numbers, in your browser: no signup, no uploads, nothing stored.
Enter your numbers and Standard Deviation Calculator works out the standard deviation, mean and variance with √(Σ(x − mean)² ÷ n) — fast, free and private, with no sign-up or uploads.
About this calculator
It computes the standard deviation as √(Σ(x − mean)² ÷ n) for a population, or ÷ (n − 1) for a sample. It matters when you need the exact relationship checked quickly rather than worked through by hand. Here is the calculation on real numbers: For 2, 4, 6, 8 (population): mean = 5, variance = ((9+1+1+9)/4) = 5, so SD = √5 = 2.236 . For your own figures, use the calculator above — same method, your inputs, computed on-device.
How to use
- Type your data set, separated by commas or spaces.
- Press Calculate to measure the spread.
- Read the sample and population standard deviations.
- Press Reset to clear the data and start again.
Why use Standard Deviation Calculator
Fast
Calculations run in your browser. No round trip to a server.
Private
Your inputs never leave your device. Nothing is uploaded.
Free
No signup, no paywall, no ads-in-results, no watermarks.
Accurate
Uses standard, well-established formulas; check critical results independently.
Mobile-ready
Optimised for phones, tablets, and desktops alike.
Transparent
Honest disclaimers wherever browser limits or regional rules apply.
Common uses
Use it for homework and assignment checks
Standard Deviation in research and report calculations
Standard Deviation in statistics and data coursework
Use it when preparing worksheets
Standard Deviation in tutoring and teaching sessions
Use it for verifying answers from a textbook
Technical notes
Standard Deviation Calculator computes the standard deviation as √(Σ(x − mean)² ÷ n) for a population, or ÷ (n − 1) for a sample.
Inputs are taken exactly as entered, so check for typos before trusting an answer.
Because it runs locally, results appear instantly with no server round-trip.
FAQ
What is the difference between sample and population standard deviation?
Sample SD divides by n - 1 and is used when your data is a sample; population SD divides by n and is used when you have the whole population.
Why do I need at least two numbers?
Sample standard deviation divides by n - 1, so it is not defined for a single value; at least two numbers are required.
Does it also show the variance?
Yes. Both the sample and population variances are shown alongside the standard deviations.
Does the Standard Deviation Calculator send my data to a server?
No. The Standard Deviation Calculator runs entirely in your browser, so nothing you enter is uploaded, stored, or shared.
Worked example
For 2, 4, 6, 8 (population): mean = 5, variance = ((9+1+1+9)/4) = 5, so SD = √5 = 2.236.