Summary

BINOM.DIST finds the probability of getting a certain number of successes in a fixed number of trials. It works best when every trial has only two possible outcomes, such as success or failure, click or no click, pass or fail.

Microsoft describes it as a binomial distribution function for independent trials with a constant probability of success. So this function makes sense only when the trial setup stays consistent from start to finish.

Syntax

=BINOM.DIST(number_s, trials, probability_s, cumulative)

number_s is the success count you want to test, trials is the total number of attempts, probability_s is the chance of success on each trial, and cumulative decides whether you want one exact result or the running total up to that result.

Arguments

• number_s - [required] The number of successes you want to measure.
• trials - [required] The total number of independent trials.
• probability_s - [required] The probability of success on each trial. This must be between 0 and 1.
• cumulative - [required] Use FALSE for the exact probability and TRUE for the probability of that number or fewer.

BINOM.DIST vs Other Functions

The last argument matters a lot here. FALSE gives the probability of exactly the number you entered. TRUE gives the cumulative probability from 0 up to that number.

Using the BINOM.DIST Function

This function is useful when the question sounds like, "What is the chance of getting this many successes out of this many tries?" That can be a review rate, a defect count, a set of correct answers, or any other setup where each trial ends in either success or failure.

It also helps to read the result in plain language before moving on. If Excel returns 0.12, that means the outcome should happen about 12% of the time under the assumptions you gave the function. When that number is very small, the result may be unusual enough to investigate.

• Use it for response rates, defect counts, and pass or fail results.
• Use FALSE for one exact success count.
• Use TRUE when you need "at most" that many successes.

Example 1 - Find an exact probability

Use FALSE when the question is about one specific success count.

=BINOM.DIST(5,10,0.5,FALSE) // Returns the chance of exactly 5 successes.

Example 2 - Find the cumulative probability

Use TRUE when you want the probability of that result or any smaller success count.

=BINOM.DIST(2,10,0.5,TRUE) // Finds the chance of getting 0, 1, or 2 successes.

Example 3 - Check a review result

This one measures the chance of an exact outcome when the success rate is already known.

=BINOM.DIST(8,10,0.7,FALSE) // Returns the chance of exactly 8 positive reviews.

Example 4 - Check a small defect risk

A cumulative result helps when you want to know the probability of staying at or below a defect limit.

=BINOM.DIST(3,50,0.02,TRUE) // Returns the chance of 3 or fewer errors.

Conclusion Recap

• Main job: BINOM.DIST returns a binomial probability for a fixed number of trials.
• Exact vs cumulative: Use FALSE for exactly that many successes and TRUE for that many or fewer.
• Best fit: Use it when each trial has only two outcomes and the success rate stays constant.
• Keep inputs valid: The probability must be between 0 and 1.
• Good use cases: Response rates, defect counts, and pass or fail results all fit well.