BINOM.DIST function
Returns the individual term binomial distribution probability. Use BINOM.DIST in problems with a fixed number of tests or trials, when the outcomes of any trial are only success or failure, when trials are independent, and when the probability of success is constant throughout the experiment. For example, BINOM.DIST can calculate the probability that two of the next three babies born are male.
Syntax
BINOM.DIST(number_s,trials,probability_s,cumulative)
The BINOM.DIST function syntax has the following arguments:

Number_s Required. The number of successes in trials.

Trials Required. The number of independent trials.

Probability_s Required. The probability of success on each trial.

Cumulative Required. A logical value that determines the form of the function. If cumulative is TRUE, then BINOM.DIST returns the cumulative distribution function, which is the probability that there are at most number_s successes; if FALSE, it returns the probability mass function, which is the probability that there are number_s successes.
Remarks

Number_s and trials are truncated to integers.

If number_s, trials, or probability_s is nonnumeric, BINOM.DIST returns the #VALUE! error value.

If number_s < 0 or number_s > trials, BINOM.DIST returns the #NUM! error value.

If probability_s < 0 or probability_s > 1, BINOM.DIST returns the #NUM! error value.

The binomial probability mass function is:
where:
is COMBIN(n,x).
The cumulative binomial distribution is:
Example
The example may be easier to understand if you copy it to a blank worksheet.
How do I copy an example?

Select the example in this article.
Important Do not select the row or column headers.
Selecting an example from Help

Press CTRL+C.

In Excel, create a blank workbook or worksheet.

In the worksheet, select cell A1, and press CTRL+V.
Important For the example to work properly, you must paste it into cell A1 of the worksheet.

To switch between viewing the results and viewing the formulas that return the results, press CTRL+` (grave accent), or on the Formulas tab, in the Formula Auditing group, click the Show Formulas button.
After you copy the example to a blank worksheet, you can adapt it to suit your needs.

