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Probability Calculator

Calculate the probability of single events, multiple independent events occurring together, and conditional probability. Results in fraction, decimal, and percentage.

Mode
Probability
As Fraction
As Percentage
Complement (1 − P)
Odds For
Frequently Asked Questions
What is probability?

A number between 0 and 1 representing likelihood of an event. 0 = impossible, 1 = certain. Fair coin flip = 0.5.

What is conditional probability?

P(B|A) is the probability of B given A has occurred.

How do I calculate probability of two events both occurring?

For independent events: P(A and B) = P(A) × P(B). Rolling 6 twice: 1/6 × 1/6 = 1/36.

What is the complement rule?

P(not A) = 1 - P(A). If rain probability is 30%, no rain probability is 70%.

What is the difference between theoretical and experimental probability?

Theoretical is calculated mathematically. Experimental is observed over many trials. They converge as trials increase.