Probability Calculator
Calculate the probability of an event occurring based on favorable and total outcomes.
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Probability
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As Percentage
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Odds (for:against)
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Probability NOT occurring
Recent Calculations
What Is Probability?
Probability measures the likelihood of an event occurring, expressed as a number between 0 (impossible) and 1 (certain).
Formula
P(A) = Number of favorable outcomes / Total number of outcomesExample
Drawing a red card from a deck: 26 favorable outcomes out of 52 total = 0.5 or 50%.
Frequently Asked Questions
What do probability values mean?
0 = impossible, 0.25 = unlikely, 0.5 = even chance, 0.75 = likely, 1 = certain.
How do I combine probabilities?
Independent events: P(A and B) = P(A) × P(B). Mutually exclusive: P(A or B) = P(A) + P(B).