Birthday Paradox
Version 1.0.0 · Updated 2026-07-28
CORE DEFINITION
In probability theory, the birthday problem asks for the probability that, in a set of n randomly chosen people, at least two will share the same birthday. The birthday paradox is the counterintuitive fact that only 23 people are needed for that probability to exceed 50%.
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In probability theory, the birthday problem asks for the probability that, in a set of n randomly chosen people, at least two will share the same birthday. The birthday paradox is the counterintuitive fact that only 23 people are needed for that probability to exceed 50%.
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The birthday paradox states that in a group of only 23 people, the probability that two share a birthday exceeds 50%, which is far from intuitive. It reveals that the number of pairs grows quadratically with the group size.
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Source support: Explicit
- en.wikipedia.orghttps://en.wikipedia.org/wiki/Birthday_problemverified
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