Probability Calculator
Probability Formulas
P(A) = favorable / total
P(A and B) = P(A) × P(B) (independent)
P(A or B) = P(A) + P(B) - P(A and B)
C(n,r) = n! / (r! × (n-r)!)
P(n,r) = n! / (n-r)!
Sources & Methodology
P(A) = Number of favorable outcomes / Total outcomesBasic probability calculation
How to Calculate Probability
The Probability Calculator helps you find the likelihood of events occurring. Calculate simple probability, combinations, permutations, and expected value. Essential for statistics, gaming, gambling odds, and decision-making.
Basic Probability Formula
Probability = (Favorable Outcomes) / (Total Possible Outcomes). A probability of 0 means impossible, 1 means certain. Express as a fraction, decimal, or percentage.
Key Probability Concepts
- Single event: P(A) = favorable / total outcomes
- AND (both events): P(A and B) = P(A) × P(B) for independent events
- OR (either event): P(A or B) = P(A) + P(B) - P(A and B)
- NOT (complement): P(not A) = 1 - P(A)
Combinations vs Permutations
Combinations (order doesn't matter): How many ways to choose r items from n? C(n,r) = n! / (r! × (n-r)!)
Permutations (order matters): How many arrangements of r items from n? P(n,r) = n! / (n-r)!
Related Calculators
Generate random numbers with our random number generator. Analyze statistical significance with the p-value calculator. Find percentages for probability conversions.
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