Conditional Probability Calculator

Calculate P(A|B) given P(A∩B) and P(B).

Fill in the fields below to calculate

P(A∩B)

Probability of A and B

P(B)

Probability of B

P(B|A)

Probability of B given A

P(A)

Probability of A

P(B)

Probability of B

Enter your values above to see the result.

Your Results

P(A|B)

Formulas

Standard:

P(A|B) = P(A∩B) / P(B)

Bayes' Theorem:

P(A|B) = [P(B|A) × P(A)] / P(B)

P(A|B) reads as "probability of A given B"

Pro Tips

Results update as you type — change any field to see the effect immediately.

Check that every value uses the same unit before comparing results.

Use the copy button to paste the conditional probability figures into a note or spreadsheet.

Nothing is sent to a server, so you can use this with private figures.