Standard Deviation Calculator
Build a STDEV.S or STDEV.P formula to measure how spread out a set of numbers is.
STDEV.S
Build a STDEV.S or STDEV.P formula to measure how spread out a set of numbers is.
Type STDEV.S when your numbers are a sample of a larger group, or STDEV.P when the range is the entire population. Any other text here produces a #NAME? error.
The cells holding your numbers. Text, TRUE/FALSE, and empty cells inside the range are skipped.
=STDEV.S(A2:A100)Worked Example
Eight test scores in A2:A9 (2, 4, 4, 4, 5, 5, 7, 9) taken as a sample of a much larger class.
=STDEV.S(A2:A9)Returns: Returns about 2.14 (2.1381 to four decimals). Switching to =STDEV.P(A2:A9) on the same numbers returns exactly 2, because it divides by 8 instead of 7.
Checks Before You Paste
- •STDEV.S divides by n-1 because a sample underestimates the spread of the group it came from; STDEV.P divides by n. STDEV.S therefore returns the larger number on any range that actually varies, and on small ranges the gap is wide: eight values give 2.14 versus 2.00 on the same data. The two agree only when every value is identical and both return 0.
- •STDEV.S returns #DIV/0! when the range holds fewer than two numbers. Text, logical values, and blanks inside a range reference are ignored rather than counted as zero, so numbers accidentally stored as text silently shrink n and skew the result with no error to warn you.
- •The legacy STDEV and STDEVP names still work in every Excel version and return exactly the same values as STDEV.S and STDEV.P. STDEVA and STDEVPA are different: they count text as 0 and TRUE as 1, which is almost never what you want.