Probability Calculator

Formula

Probability: P(A) = Favorable / Total

Independent Events: P(A and B) = P(A) × P(B)

Combinations (nCr): n! / (r!(n-r)!)

Binomial: P(X=k) = nCr × p^k × (1-p)^(n-k)

Examples

• Rolling a 4 on a 6-sided die: 1 favorable, 6 total = 16.67%
• Flipping 2 heads in 3 coin flips: n=3, k=2, p=0.5 -> 37.5%
• Choosing 3 players from a team of 10: 10C3 = 120 ways

FAQ

What is P(A or B)?

Probability of either event occurring. For mutually exclusive, P(A) + P(B).

What's the difference between Combinations and Permutations?

Permutations care about order (AB != BA). Combinations do not (AB == BA).

Can probability be negative?

No, it is always between 0 and 1 (0% to 100%).

What is complementary probability?

P(not A) = 1 - P(A).