Probability Calculator

Probability Formulas

The Single Event Probability Calculator uses the following formulas:

P(E) = n(E) / n(T) = (number of outcomes in the event) / (total number of possible outcomes)

P(E') = P(not E) = 1 - P(E)

Where:

P(E) is the probability that the event will occur,

P(E') is the probability that the event will not occur,

n(E) is the number of outcomes in the event E,

n(T) is the total number of possible outcomes.

Probability Formulas

The Multiple Event Probability Calculator uses the following formulas:

P(A) = n(A) / n(T)

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

P(B) = n(B) / n(T)

P(B') = P(not B) = 1 - P(B)

P(A ∩ B) = P(A) × P(B)

P(A ∪ B) = P(A) + P(B) - P(A ∩ B)

P(A | B) = P(A ∩ B) / P(B)

P(B | A) = P(A ∩ B) / P(A)

Where:

P(A) is the probability that event A occurs,

P(A') is the probability that event A does not occur,

P(B) is the probability that event B occurs,

P(B') is the probability that event B does not occur,

P(A ∩ B) is the probability that events A and B both occur,

P(A ∪ B) is the probability that events A or B occur,

P(A | B) is the probability that event A occurs, given that event B has occurred,

n(A) is the number of outcomes in the event A,

n(B) is the number of outcomes in the event B,

n(T) is the total number of possible outcomes.