Published by patrick honner on

My friend recently met a girl who shares a birthday with him.  He is not the romantic type, but he was definitely moved by this remarkable coincidence.

Assuming all birthdays are evenly distributed (are they?), and ignoring freaks born on February 29th, the probability that a person you meet will have the same birthday as you is 1/365, which is approximately .27%.

This is about twice as likely as getting dealt a full house in a five-card poker hand, which hardly qualifies as “fated”.  If she had his initials, too, that would be another story.

Categories: Probability

patrick honner

Math teacher in Brooklyn, New York


Nikita Zolotykh · July 7, 2010 at 1:12 pm

Funny and interesting post :).

I knew only one person with the same birthday as mine, and I think we were born the same year too.

Sam Kolins · July 7, 2010 at 5:01 pm

I read in a Ripley’s Believe It Or Not book that there is a pair of twins (I don’t know if they are identical or fraternal) both born on February 29th.

I must be pretty lucky myself, because I know TWO people born on the same day and year as I am.

Then again, put a bunch of people in a room, and the chances of this occurring shoot up almost astronomically. Very, very famous problem.

Nikita Zolotykh · July 11, 2010 at 3:06 pm

This might me a little off topic, but:
How does life work for people born on February 29th? I’ve been thinking about this for a while – do “24 year old” people born on February 29th count as “6 year old” people legally, and, therefore, can’t legally do anything that a 24 year old can do? Because if it is so, then I honestly don’t know when people born on February 29th start to really enjoy their life. (yeah, that was a little stupid of me to say, but I’m still really curious)

Although I guess legally the law “counts” them as to be born on March 1st or something to avoid such an issue.

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