698 tools
All

Dice Probability Calculator

Find the chance of rolling a chosen face exactly k times, or at least k times, on n fair dice.

 

 

 

P(exactly k)
P(at least k)

About this calculator

Use this calculator for fair, independent dice when you care about how often a particular face appears, not about the sum of the dice. Two six-siders looking for sixes, a D20, or a handful of custom dice all fit this binomial model.

Each die is a trial with success probability p = 1 / sides. Then P(exactly k) = C(n, k) p^k (1 − p)^{n − k} and P(at least k) is the sum of that PMF from k through n. Two six-sided dice and k = 1 give P(exactly one six) ≈ 0.2778 and P(at least one six) ≈ 0.3056.

Dice are assumed fair and independent. This is not the distribution of the total pips. k cannot exceed the number of dice.

Dice (n): How many dice you roll.

Sides: Faces on each die. 6 is a standard die, 20 is a D20.

Count (k): How many times you want the chosen face.

P(exactly k): Probability of exactly k of that face.

P(at least k): Probability of k or more of that face.