b2KIT

Standard Deviation & Statistics Calculator

Compute mean, median, mode, standard deviation, variance, and other descriptive statistics from a data set.

How to Use Standard Deviation & Statistics Calculator

  1. 1

    Enter your data set

    Type or paste the numbers separated by commas.

  2. 2

    View statistics

    See mean, median, mode, standard deviation, and variance.

  3. 3

    Copy the results

    Click copy to grab the calculated statistics summary.

Tested tool guide Tested browser tools Checked August 16, 2026

What Standard Deviation & Statistics Calculator does, with a checked example

Feed it a batch of numbers - quiz scores, response times, sensor readings - and it returns the standard summary statistics: count, mean, median, mode, range, variance, and standard deviation, in both the sample and population variants. Everything is computed from the values you enter, and nothing leaves the page. The most common surprise is that standard deviation comes in two flavors: dividing by n-1 (sample) or by n (population). They answer different questions, and using the wrong one is the usual source of mismatches with spreadsheets or published figures.

Worked example

A concrete input and expected output from the current implementation.

Input

4, 8, 6, 5, 3, 8

Expected output

count 6; mean 5.67; median 5.5; mode 8; range 5; sample variance 4.27; sample standard deviation 2.07; population variance 3.56; population standard deviation 1.89

The six values sum to 34, so the mean is 34/6 = 5.67. Sorted, the list is 3, 4, 5, 6, 8, 8: the median is the average of the two middle values, (5 + 6)/2 = 5.5, and the mode is 8, the only repeated value. The squared deviations from the mean sum to about 21.33; dividing by 5 gives the sample variance 4.27, dividing by 6 gives the population variance 3.56, and the standard deviations are their square roots.

How the result is produced

1

What gets computed

Each statistic is a direct formula over the entered values. The mean is the sum divided by the count. The median is the middle value of the sorted list, or the average of the two middle values when the count is even. The mode is the most frequent value, with every tied value reported if several tie. The range is the largest value minus the smallest.

2

Why two standard deviations

The sum of squared deviations from the mean is divided by the number of values for the population variance, or by the number of values minus one for the sample variance; the standard deviation is the square root of either. The n-1 divisor, called Bessel's correction, is used when the numbers are a sample of a larger population, because dividing by n would on average underestimate how much that population varies.

Good uses

  • After a test or quiz, summarize the class: the mean gives the average score and the standard deviation shows whether results cluster tightly around it or scatter widely.
  • In quality or lab work, judge whether variation between repeated measurements is small enough relative to a tolerance, or whether something changed between runs.
  • Verify numbers you got from a spreadsheet: the tool's sample and population results correspond to Excel's STDEV.S/STDEV and STDEV.P, so a mismatch usually reveals the convention or the data, not a calculation error.

Limits and checks

  • Sample versus population: most real data is a sample, so the n-1 version is usually the one to quote. The choice changes the result (2.07 versus 1.89 in the example above) and is the most common cause of disagreement with other sources.
  • Sensitivity to outliers: mean and standard deviation use every value, so one extreme entry moves both. When one number looks anomalous, compare with the median, which ignores extremes.
  • Descriptive, not inferential: the tool summarizes the entered values. It does not test whether a difference is statistically significant, assess normality, or identify outliers beyond what you decide to investigate.

Common questions

Should I use the sample or the population standard deviation?

Use the sample version when your numbers are a subset of a larger group you want to generalize about, such as twenty boxes measured to represent all boxes. Use the population version when the list is the complete group. When in doubt, the sample version fits most real-world uses; the two differ by a factor of sqrt(n/(n-1)).

Why does my result differ from Excel's?

Usually a convention mismatch. Excel's STDEV and STDEV.S return the sample standard deviation and STDEV.P returns the population version, so pick the matching mode here and the values agree to rounding. If they still differ, confirm the same values were entered in both places, since results depend on exactly which entries were counted.

References and verification

The example and behavioral notes were checked against the browser implementation. Standards and primary references below define the relevant format, formula, or platform behavior.

Related Tools