Standard Deviation Calculator
Free online Standard Deviation Calculator.
Calculator
How to Use
- Enter the required values
- Click Calculate to see the result
- Review the detailed output
Formula
Sample SD: s = sqrt[Sum(xi - xbar)^2 / (n-1)]. Population SD: sigma = sqrt[Sum(xi - mu)^2 / N]. Variance = SD squared. Measures data spread from mean.
Example Calculations
Sample Data Set
Input: Values: 10, 12, 14, 16, 18
Result: Mean: 14, Sample SD: 3.16, Population SD: 2.83
Test Scores
Input: Scores: 85, 90, 78, 92, 88, 76
Result: Mean: 84.83, SD: 6.46
Large Data Set
Input: Values: 2, 4, 4, 4, 5, 5, 7, 9
Result: Mean: 5, Sample SD: 2.0, Population SD: 1.87
About This Calculator
Free online standard deviation calculator. Calculate instantly in your browser with our easy-to-use tool. No sign-up required.
Our standard deviation calculator is free, easy to use, and provides instant results. All calculations are performed in your browser for privacy and speed.
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Frequently Asked Questions
What is standard deviation?
Measures how spread out data is from the mean. Low means clustered, high means wider spread.
Population vs sample SD?
Population divides by N, sample by N-1 (Bessel correction). Use population for all data, sample for subsets.
Real-life uses?
Finance (volatility), quality control, weather variation, and education (test score analysis).
One standard deviation meaning?
In normal distribution, ~68% of data falls within one SD of mean, 95% within two, 99.7% within three.
Can SD be negative?
No, always zero or positive since it is the square root of variance (average of squared differences).