Probability Calculator
Calculate probabilities, combinations, permutations, and conditional probabilities. Essential for statistics, games, and decision-making.
Calculate Probability
Choose a calculation type
Result
Enter values to calculate probability.
Frequently Asked Questions
What's the difference between combinations and permutations?
Combinations: order doesn't matter. Choosing 3 people from 10 for a committee = C(10,3) = 120. Permutations: order matters. Assigning 1st, 2nd, 3rd place from 10 runners = P(10,3) = 720.
How do I convert odds to probability?
If odds are 3 to 1 against, probability = 1/(3+1) = 0.25 or 25%. If odds are 3 to 1 for (3:1 on), probability = 3/(3+1) = 0.75 or 75%.
When do I multiply vs add probabilities?
Multiply for AND (both events): P(A and B) = P(A) × P(B) for independent events. Add for OR (either event): P(A or B) = P(A) + P(B) - P(A and B).
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