In this article
CONFIDENCE returns the normal margin of error for a mean. It is a compatibility function: Excel keeps it so workbooks from Excel 2007 and earlier still calculate, but Microsoft recommends CONFIDENCE.NORM for new work. Both give the same result.
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Syntax
=CONFIDENCE(alpha, standard_dev, size)| Argument | What it means |
|---|---|
alpha |
0.05 |
standard_dev |
SD |
size |
n |
Examples
Example 1
=ROUND(CONFIDENCE(0.05,A2,B2),2)Result: 2.35. See the worked example table below for more cases.
💡 For new workbooks use CONFIDENCE.NORM: it gives the same answer and is the name Microsoft keeps documenting.
CONFIDENCE in practice
Where you will use it
- Opening and checking older workbooks that use CONFIDENCE
- Understanding formulas shared by colleagues on older Excel versions
- Knowing when to swap in CONFIDENCE.NORM for clarity
Worked example
| SD | n | Formula | Result |
|---|---|---|---|
| 12 | 100 | =ROUND(CONFIDENCE(0.05,A2,B2),2) | 2.35 |
| 12 | 400 | =ROUND(CONFIDENCE(0.05,A3,B3),2) | 1.18 |
| 5 | 30 | =ROUND(CONFIDENCE(0.05,A4,B4),2) | 1.79 |
Results calculated in Excel. Same result as CONFIDENCE.NORM.
Mistakes people make
| Mistake | What to do instead |
|---|---|
| Using CONFIDENCE in new files | Prefer CONFIDENCE.NORM: same result, clearer name, and the function Microsoft keeps improving |
| Mixing old and new names in one model | Pick one style per workbook so formulas are easy to audit |
Related functions
📚 Part of the free Excel course: Beginner → Expert · Try it in the Formula Lab or ask the AI Helper.
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