In Excel: use =STDEV.S(range) for a sample, or =STDEV.P(range) when your data is the whole population.
On this page7
Put your numbers in a single column or row.
In a blank cell type =STDEV.S( and select the range, then close the bracket.
Press Enter to get the sample standard deviation.
Use =STDEV.P(range) instead if your data covers the entire population, not a sample.
What this does
Standard deviation measures how spread out your numbers are around their average — small means tightly clustered, large means widely scattered. It is in the same units as the data, so a standard deviation of 4 on test scores literally means "give or take about 4 points". STDEV.S divides by n−1 for a sample; STDEV.P divides by n when you have every member of the group. Keep the inputs visible and clearly labelled and the whole thing stays auditable — anyone who opens the file later, including you, can see at a glance exactly what feeds the result and change one assumption without hunting through the formula. The difference between a quick fix and a sheet you can trust is the extra minute you spend validating “find mean and standard deviation in excel”. Start on a copy or a tiny sample, keep the affected cells visible, and compare the result with the outcome you expected before you touch the real workbook. When a formula is involved, keep the inputs labelled beside it, reference cells instead of typing values, and apply number formatting only after the result checks out. The point is a calculation you can defend to a CFO or an auditor, but the practical win is that someone else can open the file and understand what happened without asking you.
A worked example
For the values 12, 15, 9, 21, 17, 14, the mean is 14.67 and =STDEV.S(A1:A6) returns about 4.13. So a typical value sits roughly 4 units either side of the average. Variance — the square of that — is about 17.07. Standard deviation is the workhorse of any risk, quality or performance analysis — investment volatility, process control, test-score spread. The mean tells you the centre; standard deviation tells you how much to trust it. Check the referenced cells, argument order and result type in your workbook. Start with the worked example before changing an input, then compare the changed result with the calculation you expected. An error value or a result of a different type is a reason to inspect the inputs and arguments.
In Google Sheets
Google Sheets support for this task has not been verified. Check the function, arguments and workflow in the target product before transferring the example. Matching formula notation does not establish identical behaviour. The aim was to get you unstuck fast and leave you a little more capable than a copy-paste would. The answer is at the top and the detail above shows why it holds — so the next time a colleague asks, you can answer without reaching for search. For “find mean and standard deviation in excel”, keep the input cells and the result visible while you check the formula in Excel. Follow the worked example and change one input at a time. The steps explain the workbook calculation; this page does not run a live calculator for that task.
Common mistakes
- Using STDEV.P on a sample (or STDEV.S on a full population), which biases the spread.
- Assuming text, logical values or blanks in a referenced range count as zero — STDEV.S and STDEV.P ignore them.
- Comparing standard deviations of data measured in different units.
- Confusing standard deviation with the standard error of the mean — they answer different questions.
Frequently asked questions
STDEV.S or STDEV.P?
Use STDEV.S (sample, n−1) when your data is a sample drawn from a larger group — the usual case. Use STDEV.P (population, n) only when you have every single member.
What does a high standard deviation mean?
That values vary a lot around the mean — more risk or inconsistency. A low value means results are predictable and tightly grouped.
Is the old STDEV function still fine?
STDEV is the legacy name for STDEV.S and still works for backward compatibility, but new sheets should prefer the explicit STDEV.S / STDEV.P.
Which values does STDEV.S count?
In a referenced range, STDEV.S and STDEV.P count numbers and ignore blanks, text and logical values. Values typed directly as arguments follow different rules: numbers, numeric text and logical values can count, while non-numeric text can cause an error. If a cell holds numeric-looking text such as "5", convert it to a number first (for example with VALUE in a helper column), then use STDEV.S or STDEV.P on the numeric range. STDEVA and STDEVPA can include logical values, but do not convert referenced text "5" into the number 5; text may count as zero.
Other ways people ask this
People reach this page typing “how to calculate mean and standard deviation in excel” and “how to find the mean and standard deviation in excel”, among other phrasings; whichever wording you used, the fix above is the one you want.
Why do people search for this in so many different ways?
Because the same task has many names. “how to calculate mean and standard deviation in excel”, “how to find the mean and standard deviation in excel” all point at the one operation explained on this page, which is why they all lead here.