A free online probability calculator for single events, multiple events, combinations, and permutations. Compute probability as fraction, decimal, and percentage. Calculate odds, "all events occur" and "at least one occurs" probabilities. Find combinations C(n,k) and permutations P(n,k) with factorial display.
Choose a mode: Single Event, Multiple Events, Combinations, or Permutations.
Enter the favorable and total outcomes or n and k values.
View results as percentage, fraction, decimal, and odds.
Copy results to clipboard as needed.
Combinations (C) count selections where order does not matter. Permutations (P) count selections where order matters. For example, picking 2 from {A,B,C}: C=3 (AB,AC,BC) vs P=6 (AB,BA,AC,CA,BC,CB).
The probability of at least one event occurring in n trials is 1 - (1-p)^n, where p is the probability of a single event.
Free online tool — works in your browser, no sign-up required. Start using it right now.
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