Probability Calculator
Permutations, combinations, binomial probabilities, normal distribution values and dice-sum distributions.
| n! (factorial) | 3628800 |
|---|---|
| P(n, r) permutations | 720 |
| C(n, r) combinations | 120 |
How to use
- Pick a tab: permutations & combinations, binomial, normal distribution, or dice sums.
- Enter n and r for counting, or n, k and p for the binomial distribution.
- For the normal distribution, get Φ(z) or the probability for an interval a < Z < b.
- For dice, choose the count and sides to see the full distribution of sums as a table and bars.
Notes
Φ(z) for the normal distribution uses the Abramowitz–Stegun approximation (error below 7.5×10⁻⁸). The binomial P(X ≥ k) is computed as 1 − P(X ≤ k−1). Dice distributions are exact enumerations, for up to 20 dice. Factorials and permutations may switch to exponential notation for large n.
FAQ
- Are Poisson or t distributions included?
- No. This tool focuses on counting, the binomial and normal distributions, and dice sums.
- Can dice have any number of sides?
- Any number of sides from 2 upward works, for up to 20 dice. Larger configurations take slightly longer to enumerate.