Spreadsheet Practice

How to calculate the standard error of the mean in Excel

Formula (Excel and Google Sheets)

=STDEV.S(B2:B9)/SQRT(COUNT(B2:B9))

Divide the sample standard deviation by the square root of the count: =STDEV.S(B2:B9)/SQRT(COUNT(B2:B9)).

Result on the example
0.660 in E1
Works in
Every current version
Google Sheets
Same formula

See it work

The formula is already in E1. Change any input and the result updates, or edit the formula to experiment.

How it works

The standard deviation (about 1.87 g) describes how much single samples vary. The standard error describes how precisely the average (500.7 g) is known, and it shrinks as you take more samples: dividing by the square root of 8 gives about 0.66 g.

=STDEV.S(B2:B9)/SQRT(COUNT(B2:B9))

Result0.6600865744

  1. B2:B98 rows × 1 col: 502.1, 498.7, 501.4, 499.9, …

    A range: 8 cells in one column.

  2. STDEV.S(B2:B9)1.867006772

    STDEV: Sample standard deviation (same as STDEV.S).

    • number1B2:B98 rows × 1 col: 502.1, 498.7, 501.4, 499.9, …
  3. COUNT(B2:B9)8

    COUNT: Counts cells that contain numbers.

    • value1B2:B98 rows × 1 col: 502.1, 498.7, 501.4, 499.9, …
  4. SQRT(COUNT(B2:B9))2.828427125

    SQRT: Square root.

    • numberCOUNT(B2:B9)8
  5. STDEV.S(B2:B9)/SQRT(COUNT(B2:B9))0.6600865744

    The / operator divides.

In Google Sheets

The same formula works in Google Sheets: =STDEV.S(B2:B9)/SQRT(COUNT(B2:B9)). We ran it in Google Sheets mode on the same data and it returns 0.660.

Other ways to do it

Each one was run on the same example sheet.

FormulaResultWhen to use it
=SQRT(VAR.S(B2:B9)/COUNT(B2:B9))0.660The same value from the variance.

Common mistakes

  • Using COUNTA counts text and labels, and ROWS counts blanks. COUNT counts only the numbers that STDEV.S used.
  • STDEV.P in place of STDEV.S understates the standard error for a sample.

Try it yourself

Same data, empty answer cell. Your formula is graded instantly, then re-checked on changed data, so a typed-in number won't pass.

Calculate the standard error of the mean

In E1, calculate the standard error of the mean fill weight for the samples in B2:B9.

Questions

How do I calculate a 95% confidence interval?

For larger samples use the mean ± 1.96 × SE; for small samples, =CONFIDENCE.T(0.05,STDEV.S(B2:B9),COUNT(B2:B9)) gives the margin.

Is there a STDERR function?

Not for the mean. STEYX is the standard error of a regression prediction, which is different.

Checked by running on 2026-10-30: every formula and result on this page was calculated by the Spreadsheet Practice formula engine, in both Excel and Google Sheets modes.