Probability Calculator

Calculate simple, compound, conditional and independent probabilities, with the rule used and tree or table shown. Try “probability of two heads and a 6 on a die”.

Try an example:

What you can do with the Probability Calculator

Simple, compound, conditional and independent events.

Enter your values or describe the problem in the calculator above. Review the result and the explanation before using it in homework, study or practical calculations.

Example input

e.g. probability of two heads and a 6 on a die

How the Probability Calculator works

  1. List the outcomes or events and decide whether they are independent.
  2. Multiply for AND with independent events, add for OR (subtracting any overlap).
  3. Give the answer as a fraction, decimal or percent.

Frequently asked questions

How do I find the probability of A and B?

For independent events, P(A and B) = P(A) × P(B). Otherwise use P(A) × P(B | A).

What is conditional probability?

P(A | B) = P(A and B) ÷ P(B), the chance of A given that B has happened.

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Math Solver can make mistakes. Please double-check important steps and calculations.