Birthday Paradox Calculator

Calculate the probability that at least two people in a group share the same birthday — the famous 'birthday paradox,' where the probability climbs surprisingly fast, reaching over 50% with just 23 people.

Inputs
Results
Probability of a Shared Birthday
50.73

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Formula

P(match) = 1 − ∏ᵢ₌₀ⁿ⁻¹ (365 − i) / 365

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