CONFIDENCE.T Function in Excel: Margin of Error for Small Samples

CONFIDENCE.T Function in Excel: Margin of Error for Small Samples 1
⏱ 1 min readUpdated 5 October 2026

StatisticsLevel: ExpertAvailable in: Excel 2010+

In this article
  1. Syntax
  2. Examples
  3. Example 1
  4. CONFIDENCE.T in practice
  5. Where you will use it
  6. Worked example
  7. Mistakes people make
  8. Related functions

CONFIDENCE.T is the margin of error using the t-distribution, correct for small samples (under ~30) where CONFIDENCE.NORM is too narrow.

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Syntax

=CONFIDENCE.T(alpha, standard_dev, size)
Argument What it means
alpha 0.05 for 95%
standard_dev Sample SD
size n

Examples

Example 1

=ROUND(CONFIDENCE.T(0.05,A2,B2),2)

Result: 8.58. See the worked example table below for more cases.

CONFIDENCE.T in practice

Where you will use it

  • ± range for the average of 10 test results
  • Pilot surveys
  • Lab measurements

Worked example

SDnFormulaResult
1210=ROUND(CONFIDENCE.T(0.05,A2,B2),2)8.58
1230=ROUND(CONFIDENCE.T(0.05,A3,B3),2)4.48
55=ROUND(CONFIDENCE.T(0.05,A4,B4),2)6.21

Results calculated in Excel.

Mistakes people make

MistakeWhat to do instead
Using NORM for small samplesMargins come out too small
n of 1#DIV/0!

CONFIDENCE.NORM · T.INV.2T

📚 Part of the free Excel course: Beginner → Expert · Try it in the Formula Lab or ask the AI Helper.

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