Free Online Same Birthday Probability Calculator: Unravel the Birthday Paradox

Calculate the Probability of a Shared Birthday

Enter a number between 1 and 365 (excluding leap years).

Calculation Results

Ever wondered about the odds of two people in a room sharing a birthday? Our Same Birthday Probability Calculator helps you instantly compute this fascinating statistical phenomenon, known as the Birthday Paradox. Discover the surprising likelihood even in small groups.

Formula:

The probability (P) of at least two people sharing a birthday in a group of 'n' people is calculated as:

P(n) = 1 - [ (365! ) / ( (365 - n)! * 365n ) ]

Where:

  • P(n) = Probability of at least two people sharing a birthday.
  • n = Number of people in the group.
  • ! denotes the factorial function.
  • We assume 365 days in a year (ignoring leap years for simplicity).

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