Probability Calculator

Calculate the probability of events A and B (intersection, union, either, neither, or conditional) assuming independence. Enter each probability between 0 and 1, then choose the operation.

Your Result

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ResultWhat it means?
0ImpossibleThe probability is 0 — the event cannot occur.
< 10%Very unlikelyA probability below 10% — the event is rare but possible.
10 – 40%UnlikelyA probability between 10% and 40% — the event is not expected.
40 – 60%Roughly evenA probability between 40% and 60% — the event is a coin flip.
60 – 90%LikelyA probability between 60% and 90% — the event is expected.
≥ 90%Very likelyA probability of 90% or higher — the event is nearly certain.
1CertainThe probability is 1 — the event will occur.
—No resultInputs are out of range or missing.

Probability Formulas (independent events)

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Intersection: P(A∩B) = pA·pB. Union: P(A∪B) = pA + pB − pA·pB. Either: pA + pB − 2·pA·pB. Neither: (1−pA)·(1−pB). Conditional: pA (independent).

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