NEGBINOMDIST Function

All versions (legacy) Compatibility

The Excel NEGBINOMDIST function returns the negative binomial distribution — the probability of a number of failures before a target number of successes. It is a legacy function; Microsoft replaced it in Excel 2010 with NEGBINOM.DIST, which adds a cumulative option.

Quick answer:

=NEGBINOMDIST(10,5,0.25) probability ≈ 0.0550

Syntax

=NEGBINOMDIST(number_f, number_s, probability_s)

Argument		Description
`number_f`	Required	The number of failures.
`number_s`	Required	The threshold number of successes.
`probability_s`	Required	The probability of a success on each trial, between 0 and 1.

How to use it

NEGBINOMDIST answers: what is the probability of seeing exactly number_f failures before the number_s-th success, when each trial succeeds with probability probability_s? The legacy function has no cumulative argument — it always returns the exact-count probability.

=NEGBINOMDIST(10,5,0.25) // 10 failures before 5th success ≈ 0.0550

=NEGBINOMDIST(2,3,0.5) // ≈ 0.1875

Both number_f and number_s are truncated to integers and must be ≥ 0, with number_s ≥ 1, and probability_s between 0 and 1.

Use NEGBINOM.DIST in Excel 2010 and later. The modern NEGBINOM.DIST adds a fourth cumulative argument for a running total. NEGBINOMDIST is kept only for backward compatibility.

Try it: interactive demo

Live demo

Pick a NEGBINOMDIST example to see the formula and its result.

example

Result:

Practice workbook

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Frequently asked questions

Should I use NEGBINOMDIST or NEGBINOM.DIST?

Use NEGBINOM.DIST in Excel 2010 or later. It accepts the same three arguments plus a cumulative flag; NEGBINOMDIST is retained only for older workbooks.

What exactly does NEGBINOMDIST count?

It returns the probability of exactly number_f failures occurring before the number_s-th success, given a per-trial success probability of probability_s.

Why does the legacy version have no cumulative argument?

The original function returns only the exact-count probability. For a running total, switch to NEGBINOM.DIST and set its cumulative argument to TRUE.

What are the argument limits?

number_f and number_s are truncated to integers and must be non-negative (with at least one success required), and probability_s must be between 0 and 1.

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Related functions: NEGBINOM.DIST · BINOMDIST · HYPGEOMDIST · POISSON · COMBIN