How to Calculate Standard Deviation in Excel
Use STDEV.S or STDEV.P in Excel, choose the right one for your data, and check the result against a worked example.
In Excel, calculate standard deviation with
STDEV.S(range)for sample data orSTDEV.P(range)for a full population. Select the numeric cells, choose the function that matches your data, and Excel returns the spread in the same unit as the original values.
Choose STDEV.S or STDEV.P first
The important choice is sample versus population. Use STDEV.S when your data is a sample from a larger group. Use STDEV.P when your data contains every value in the group you care about.
STDEV still works in Excel for compatibility, but STDEV.S is clearer because it names the sample case directly.
How to enter the formula
Put your data in one column or row, click an empty cell, type the function, select the range, and press Enter. Use a cell range rather than typing every number into the formula so the result updates when your data changes.
For a complete population, change only the function name.
Worked example you can check
Use a small data set so the result is easy to verify outside Excel. The sample formula divides by one fewer than the number of values, while the population formula divides by the full count.
The population standard deviation uses the full count.
The sample standard deviation uses one fewer in the divisor.
Those two results are different on purpose. The sample version is larger because it corrects for estimating spread from only part of a larger population.
Clean the range before trusting the result
Excel ignores text in many statistical functions, but a messy range can still hide bad data. Check that every value you meant to include is inside the range and that no heading, total row, or unrelated number slipped in.
If your result looks too small or too large, inspect the selected cells first. Range mistakes are more common than formula mistakes.
What the number means
Standard deviation is in the same unit as the original data. If your data is test scores, the standard deviation is score points. If your data is delivery time in minutes, the standard deviation is minutes.
The average alone can hide spread. Two data sets can have the same mean and very different standard deviations.
Common Excel mistakes
Using the wrong function changes the answer. STDEV.S and STDEV.P are not interchangeable. Decide whether the range is a sample or a full population before typing the formula.
Selecting the wrong range is silent. Excel will still return a number if you leave out a value or include an unrelated one.
Rounding the source cells can change the result. If your displayed cells are rounded but the underlying values are not, Excel calculates from the underlying values.
Comparing standard deviations across different units can mislead. Use the coefficient of variation when you need to compare relative spread across different scales.
Common questions
Use STDEV.S for a sample and STDEV.P for a full population. If you are unsure, STDEV.S is usually the safer choice because most data sets are samples from a larger group.
The formula is =STDEV.S(range). Replace range with the cells that contain your data, such as A2:A10.
STDEV.S divides by n − 1, while STDEV.P divides by n. The smaller divisor makes the sample estimate larger so it better estimates population spread from sample data.
The ordinary STDEV.S and STDEV.P functions can include hidden rows depending on how the sheet is set up. For filtered lists, verify the selected cells or use a workflow designed for visible cells only.
Excel makes standard deviation a one-cell formula, but the hard part is choosing the right function and range. Use the standard deviation calculator when you want the same sample-versus-population choice with the working shown.
