What is the complement probability?

The complement is the probability that the event does NOT happen. If P(A) = 0.3, then P(not A) = 0.7.

How are odds different from probability?

Probability is favorable / total. Odds express the ratio of favorable to unfavorable outcomes, e.g. 1 to 4.

What if favorable outcomes exceed total outcomes?

The tool flags this as an invalid input since probability cannot exceed 1.

Probability Calculator

Calculate probability as fraction, decimal, percentage, and odds.

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Favorable outcomesTotal outcomes

Enter favorable and total outcomes above to calculate probability.

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FAQ

What is the complement probability?: The complement is the probability that the event does NOT happen. If P(A) = 0.3, then P(not A) = 0.7.
How are odds different from probability?: Probability is favorable / total. Odds express the ratio of favorable to unfavorable outcomes, e.g. 1 to 4.
What if favorable outcomes exceed total outcomes?: The tool flags this as an invalid input since probability cannot exceed 1.

Enter the number of favorable outcomes and total outcomes to instantly compute the probability as a simplified fraction, decimal, and percentage. Also shows the odds in X-to-Y format and the complement (probability of the event NOT occurring). Great for statistics, games, and quick sanity checks.