Standard Deviation Calculator
Enter at least two numbers. Uses the sample formula common in intro statistics.
Sample standard deviation
Uses n − 1 denominator (sample SD). Enter at least two numbers.
How this is calculated
Mean μ = average of values. Sample variance = Σ(x−μ)² ÷ (n−1). SD = √variance.
When to use it
- Spread of lab repeats.
- Quality control snapshots.
Frequently asked questions
Population vs sample?
This tool uses sample (n−1). Population SD would use n.
Two numbers minimum?
Yes—n−1 must be positive.
