Probability Calculator

You can use this Probability Calculator to determine the probability of single and multiple events. Enter your values in the form and click the "Calculate" button to see the results.

Single Event Probability Calculator

Results
Single Event ProbabilityValue (decimal)Value (percent)
P(E)--
P(E')--

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.

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Multiple Event Probability Calculator (A & B are independent events)

Results
Multiple Event ProbabilityValue (decimal)Value (percent)
P(A)--
P(A')--
P(B)--
P(B')--
P(A ∩ B)--
P(A ∪ B)--
P(A | B)--
P(B | A)--

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.

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