Why Use This Tool?
Standard deviation measures how spread out your data is around the mean — the single most quoted statistic after the average. This calculator computes both the population and the sample versions (they divide by n versus n−1), plus variance, mean, median, and mode in the same pass.
Paste values separated by spaces, commas, or newlines — whatever format your spreadsheet or export produced. Everything computes locally, so datasets from internal reports stay on your machine.
How It Works
- Paste your dataset with any common separator.
- Read the population and sample standard deviations side by side.
- Use the mean, median and mode to understand the shape, not just the spread.
Frequently Asked Questions
What is standard deviation?
The average distance of your data points from the mean. A small SD means values cluster tightly; a large SD means they're spread widely across the range.
What's the difference between population and sample standard deviation?
Population SD divides by n; sample SD divides by n−1 to correct for estimating from a subset. Use sample SD unless your data is the entire population.
What is the mode?
The most frequent value in the dataset. A dataset can have one mode, several (like 4 and 5 both appearing most here), or none if all values are unique.
Tips & Things to Watch
- Sample SD is the default choice for real-world data — you rarely have the whole population.
- Mean plus SD describes a normal distribution completely.
- A big gap between mean and median signals outlier values skewing the data.