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:

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.

More Statistics & Probability calculators

Statistics CalculatorMean, median, mode, range, quartiles and standard deviation. Permutations & CombinationsCounting arrangements and selections, factorials. Binomial ProbabilityProbability of k successes in n trials. Normal Distribution & Z-scoreZ-scores, percentiles and areas under the bell curve. Linear Regression & CorrelationLine of best fit, r value and predictions.

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