BINOM.INV Function in Excel: Smallest Count Reaching a Probability

BINOM.INV Function in Excel: Smallest Count Reaching a Probability 1
⏱ 1 min readUpdated 5 October 2026

StatisticsLevel: ExpertAvailable in: Excel 2010+

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

BINOM.INV returns the smallest number of successes whose cumulative probability reaches the target, e.g. how many defects is ‘unusual’.

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Syntax

=BINOM.INV(trials, probability_s, alpha)
Argument What it means
trials n
probability_s Success chance
alpha Target cumulative probability

Examples

Example 1

=BINOM.INV(A2,B2,C2)

Result: 6. See the worked example table below for more cases.

BINOM.INV in practice

Where you will use it

  • Control limits for defects in quality checks
  • Stock enough units to cover 95% of demand days
  • Alert thresholds

Worked example

TrialspalphaFormulaResult
1000.030.95=BINOM.INV(A2,B2,C2)6
200.20.5=BINOM.INV(A3,B3,C3)4
5000.010.99=BINOM.INV(A4,B4,C4)11

Results calculated in Excel.

Mistakes people make

MistakeWhat to do instead
alpha above 1#NUM!
Expecting a probability backIt returns a count

BINOM.DIST

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

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