In Excel: use =STDEV.S(range) for a sample, or =STDEV.P(range) when your data is the whole population.
n = 6 · mean = 14.67
Variance = 17.067
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 “put standard deviation in excel graph”. Start on a copy or a tiny sample, keep the affected chart visible, and compare the result with the tool above 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 visual that makes the number obvious at a glance, 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. Paste your own list into the tool above and both update instantly. 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. A practical tip before you scale it up: build it once on a small block of test data, confirm the number against the tool on this page, and only then point it at your real sheet. That one habit catches almost every mistake while it is still cheap to fix, long before a wrong figure reaches a report or a colleague.
In Google Sheets
Google Sheets handles this almost identically to Excel. The formula syntax above is the same, and the menu lives under a slightly different label rather than a ribbon tab. Use the platform toggle at the top of the page to switch every keyboard shortcut between Windows and Mac, and expect at most cosmetic differences in naming. Nothing on this page is behind a login: the tool runs entirely in your browser, the formula is shown in full with one-click copy, and the steps work the same on Windows and Mac. That is the whole promise here — the exact answer, a way to prove it on your own numbers, and just enough context to make it stick. If you take one thing from this page on “put standard deviation in excel graph”, make it the habit rather than the keystrokes: set the problem up with labelled inputs, reference those cells, and let Excel do the recomputing. Bookmark the page for the syntax, but do the example once in a blank sheet and check it against the tool above — five minutes of hands-on practice fixes the method in memory far better than re-reading, and it surfaces the small snags while they are still harmless. After that the technique is genuinely yours: faster than searching for it again, and reliable enough to drop into work that other people depend on.
Common mistakes
- Using STDEV.P on a sample (or STDEV.S on a full population), which biases the spread.
- Including text or blank cells in the range, which can skew or error the result.
- 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.
Other ways people ask this
On the way here you may have searched this as “how do you put standard deviation on an excel graph” and “how to put standard deviation on a graph in excel” — it is all the same task, and this page is the single, complete answer to it.
Why do people search for this in so many different ways?
Because the same task has many names. “how do you put standard deviation on an excel graph”, “how to put standard deviation on a graph in excel” all point at the one operation explained on this page, which is why they all lead here.