Standard Deviation Calculator
Paste or type a list of numbers and get a full descriptive-statistics summary, updated live as you edit.
Enter at least one number to see the statistics.
How it works
- Paste your numbers into the box — separate them with commas, spaces, new lines or semicolons.
- Read the live results: sample and population standard deviation, variance, mean, median, quartiles and more.
- Click Copy table to copy the complete results as tab-separated text for a spreadsheet or report.
Frequently asked questions
- What is the difference between sample and population standard deviation?
- Population standard deviation divides the sum of squared deviations by n and describes a complete data set. Sample standard deviation divides by n − 1 (Bessel’s correction) because a sample tends to underestimate the true spread. Use the sample version whenever your data is a subset drawn from a larger group.
- Which number formats and separators does the calculator accept?
- You can separate values with commas, spaces, tabs, new lines or semicolons, and mix them freely — pasted spreadsheet columns work directly. Decimal points, negative numbers and scientific notation such as 1.2e3 are all recognized. Anything that is not a valid number is simply ignored and counted as skipped.
- How are the quartiles Q1 and Q3 calculated?
- This tool uses the common median-split (exclusive) method: the data is sorted, Q1 is the median of the lower half and Q3 the median of the upper half, excluding the overall median when the count is odd. Other conventions, such as linear interpolation used by some spreadsheets, can give slightly different values for small data sets.
- Is my data uploaded anywhere when I use this calculator?
- No. Every statistic is computed by JavaScript running in your own browser tab, and the page makes no network requests with your data. You can even load the page, disconnect from the internet, and keep calculating — nothing you paste ever leaves your device.
- What are standard error and coefficient of variation used for?
- The standard error of the mean (sample SD divided by √n) estimates how much the sample mean would vary across repeated samples, so it shrinks as you collect more data. The coefficient of variation expresses the SD as a percentage of the mean, letting you compare relative spread between data sets measured in different units or scales.
About this tool
This standard deviation calculator turns a raw list of numbers into a complete descriptive-statistics report. Paste values from a spreadsheet, a lab notebook or a survey export, and it instantly shows the count, sum, minimum, maximum and range, the mean, median and mode, the quartiles Q1 and Q3 with the interquartile range, and both the sample and population versions of variance and standard deviation. It also reports the standard error of the mean and the coefficient of variation, two figures that are frequently needed in coursework and research but missing from basic calculators.
Everything runs client-side in your browser. The parser accepts numbers separated by commas, spaces, tabs, semicolons or line breaks, so a column copied straight out of Excel or Google Sheets works without cleanup; invalid tokens are skipped and reported rather than silently breaking the result. Because no data is transmitted to any server, the tool is safe to use with confidential measurements, grades or financial figures. Results recalculate live on every keystroke, and the formulas for each standard deviation are displayed next to the values so you can see exactly what was computed.
The distinction between sample and population statistics matters more than most people expect. If your numbers represent every member of the group you care about — for example, the test scores of one specific class — the population formula (dividing by n) is correct. If they are a sample meant to represent something larger — 50 measurements out of a production run of thousands — the sample formula (dividing by n − 1) gives an unbiased estimate of the true variance. The calculator shows both, along with a short worked explanation, so you can pick the right one and justify the choice.
Practical tip: check the skipped-token count after pasting. If it is higher than expected, your data may contain thousands separators or units (like “12 kg”) that need removing. For skewed data, compare the mean with the median and look at the IQR — a large gap between them signals outliers, and in that case the median and IQR often describe your data better than the mean and standard deviation.