Probability Calculator
Combinations, permutations and binomial probability.Math & StatisticsProbability Calculator
Combinations C(n,k), permutations P(n,k) and the binomial probability of exactly k successes in n trials.
About this tool
C(n,k), P(n,k) and — when you supply a success probability p — the binomial probability of exactly k successes in n independent trials. Definitions stated on the page.
How to use the Probability Calculator tool
- Enter n and k. Integers with 0 at or below k at or below n.
- Optionally add p. For the binomial probability of exactly k successes.
- Read the values. Combinations, permutations and the probability.
Supported formats
Input
- Plain text or file input
Output
- Converted or analysed output
Inputs are validated before anything is processed. Invalid values and unsupported files are rejected with a clear error instead of failing silently.
Frequently asked questions
What is the difference between C and P?
Combinations ignore order; permutations count every ordering.
Which formula is the binomial?
C(n,k) times p to the k times (1-p) to the (n-k) — exactly k successes.
Why cap n at 5000?
Intermediate values overflow ordinary floats beyond that.
Privacy
Everything you enter stays in this browser tab. There is no upload endpoint for tool inputs, no account, and no server-side copy of your text or files. Results are produced locally and disappear when you close the page.
No account is required and no file is ever uploaded. See the privacy policy for details about analytics and the limited data this site stores.
Known limitations
- Single binomial term only; cumulative probabilities are not computed.
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