Probability Calculator

Calculate probabilities, permutations, and combinations instantly with step-by-step solutions.

  • Basic probability — find P(A) from favorable and total outcomes
  • Permutations — count ordered arrangements (P(n, r))
  • Combinations — count unordered selections (C(n, r))

P(A) = favorable outcomes ÷ total outcomes

Formulas Used

Basic probability

Permutations

Combinations

How to Use This Calculator

  1. Select a mode — basic probability, permutations, or combinations
  2. Enter your values in the input fields
  3. See the result with a complete step-by-step breakdown

When to Use Each Mode

  • Basic probability — “What is the chance of rolling a 6?” (1 favorable out of 6 total)
  • Permutations — “How many ways can 3 people finish 1st, 2nd, 3rd out of 10?” (order matters)
  • Combinations — “How many ways can I choose 3 people for a committee of 10?” (order doesn’t matter)