Frequently Asked Questions
Everything you need to know about the Binomial Distribution Calculator.
What is a binomial distribution?
It models the number of successes in a fixed number of independent trials, each with the same probability of success.
What do n and p represent?
n is the number of trials, and p is the probability of success on each individual trial.
What's the difference between "exactly," "at most," and "at least"?
"Exactly k" is a single outcome's probability; "at most k" sums probabilities from 0 to k; "at least k" sums from k to n.
How is the mean of a binomial distribution calculated?
As n ร p, the expected number of successes.
Can I find a probability for a range of successes?
Yes, the "between" mode sums probabilities across a range k1 to k2.
Does it show the formula?
Yes, the binomial PMF formula is shown with your n, k, and p values substituted in.
Does it show a chart?
Yes, a bar chart plots the probability of every possible outcome, with your queried region highlighted.
What if n is large?
The calculator uses exact combinatorics to avoid precision loss even for moderately large n.
Is my data stored?
No, everything runs client-side in your browser.
Is it free?
Yes, completely free with no sign-up or limits.