What is the syntax for POISSON.DIST in Excel?

The syntax for POISSON.DIST is: =POISSON.DIST(x, mean, cumulative)

What is POISSON.DIST used for?

POISSON.DIST calculates probabilities for count data - the number of events occurring in a fixed interval when events happen independently at a constant average rate. Examples: calls per hour, defects per batch, website visits per minute.

When should I use Poisson distribution?

Use Poisson when: counting discrete events in a continuous interval, events are independent, the average rate is constant, and two events can't occur at exactly the same instant. Classic examples: radioactive decay, customer arrivals, typos per page.

How do I calculate probability of at least n events?

For P(X ≥ n), use =1 - POISSON.DIST(n-1, mean, TRUE). Example: If average is 5 calls/hour, probability of at least 8 calls: =1-POISSON.DIST(7, 5, TRUE). The cumulative=TRUE gives P(X ≤ 7), so 1 minus that gives P(X ≥ 8).

Statistical

POISSON.DIST Function in Excel

Returns the Poisson distribution.

Syntax

=POISSON.DIST(x, mean, cumulative)

Arguments

x (required): Number of events
mean (required): Expected number of events
cumulative (required): TRUE for CDF, FALSE for PMF

Examples

=POISSON.DIST(2, 5, FALSE) - Poisson probability - Result: 0.084

POISSON.DIST for data analysis

Confirm whether you need entire columns, filtered subsets, or distinct values.
Use [COUNTIFS](/functions/countifs/) and [SUMIFS](/functions/sumifs/) for multi-criteria metrics.
Pivot tables complement single-cell statistical formulas for exploration.

Common errors

#NUM! if x < 0 or mean < 0

Use cases

Event counting
Queuing theory
Rare events

Frequently asked questions

What is POISSON.DIST used for? POISSON.DIST calculates probabilities for count data - the number of events occurring in a fixed interval when events happen independently at a constant average rate. Examples: calls per hour, defects per batch, website visits per minute.
When should I use Poisson distribution? Use Poisson when: counting discrete events in a continuous interval, events are independent, the average rate is constant, and two events can't occur at exactly the same instant. Classic examples: radioactive decay, customer arrivals, typos per page.
How do I calculate probability of at least n events? For P(X ≥ n), use =1 - POISSON.DIST(n-1, mean, TRUE). Example: If average is 5 calls/hour, probability of at least 8 calls: =1-POISSON.DIST(7, 5, TRUE). The cumulative=TRUE gives P(X ≤ 7), so 1 minus that gives P(X ≥ 8).

Editorial review

Reviewed by Excel.Directory Editorial Team. Updated May 2026.