Probability calculator

Binomial probability

P(X=k) = C(n,k) × p^k × (1−p)^(n−k)

Probability of exactly k successes in n independent trials, each with probability p.

Example: P(3 heads in 10 coin flips) = C(10,3) × 0.5³ × 0.5⁷ ≈ 0.1172.

Dice probability

For 2 dice, the probability of rolling a sum of 7 is 6/36 = 1/6 ≈ 16.7%. Sum of 7 is the most likely outcome with 2 dice.

Basic probability rules

P(A or B) = P(A) + P(B) − P(A and B)

P(A and B) = P(A) × P(B|A)

P(not A) = 1 − P(A)