Independent Events Calculator

Use this calculator when two events A and B do not influence each other: the chance of both, the chance of at least one, and the chance that A does not occur. Coin-and-die sketches, independent quality checks, and simple probability homework are typical.

The formulas, assuming independence, are: P(A and B) = P(A) P(B), P(A or B) = P(A) + P(B) − P(A) P(B), and P(not A) = 1 − P(A). Enter probabilities as proportions from 0 to 1. With P(A) = 0.3 and P(B) = 0.4, P(and) = 0.12, P(or) = 0.58, and P(not A) = 0.70.

If A and B are not independent, P(A and B) is not the product and these results will be wrong. P(or) here is the inclusive or. Complementary B is not reported.

P(A): Probability of event A, 0 to 1.

P(B): Probability of event B, 0 to 1, independent of A.

P(A and B): Joint probability under independence.

P(A or B): Probability of at least one of A or B.

P(not A): Complement of A.