Binomial Probability Calculator

Find the probability of exactly or at most successes with the binomial distribution

Trials n

Success probability p (0 to 1)

Successes k

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How to use

Enter the number of trials n.
Enter the success probability p for one trial as a decimal (50% = 0.5).
Enter the number of successes k.
The exactly, at most and at least probabilities will show below.

Note: Formula: P(X = k) = C(n, k) x p^k x (1-p)^(n-k). The calculation uses a stable recurrence so it does not overflow even for large n.