How rare is your birthday? In the United States, births cluster hardest in mid September, with September 9 and September 19 repeatedly ranking as the single most common birthdays in the country. The rarest birthday overall is February 29, followed by December 25 and January 1. See the full ranking of America's most and least common birthdays for the bigger picture.
Enter your birth date below to see roughly where your day ranks among all 366 possible birthdays, how many people share it, and how it compares to the national average.
Pick your birthday; the tool compares day-and-month against the national birth distribution provided by this article.
Pick a date to start.
I have written birthday speeches for people born on a random Tuesday in June and for people born on February 29, and the material is never the same. A common September birthday is easy to laugh about, since half the room shares it. A rare date practically writes its own opening line.
Grace Whitfield
How the birthday rarity calculator works
The calculator starts with the current annual number of live births in the United States, 3,628,934 according to the CDC's National Center for Health Statistics, then spreads that total across the calendar using the real monthly birth pattern.1 Specific dates get an extra adjustment, since holidays and Leap Day behave nothing like an average day that month. Together, both layers give every one of the 366 possible birthdays a rank from most common to rarest.
Which months are strongest for US births
September has topped the monthly birth charts for decades, and not narrowly. One ranking of decades of birth data found that September dates claimed 14 of the top 25 most common birthdays nationwide, with August and July close behind.2 February sits at the bottom of the year, even after adjusting for its shorter length.
Why September takes the crown
Work back roughly forty weeks from a September birthday and you land on the winter holidays. Analysts who have studied the same NCHS birth records point to that stretch, from Christmas through New Year, as the likely conception window behind the late summer peak, with more downtime and less of the daily routine that normally gets in the way.3 It is a pattern rather than a law, but it shows up year after year.
The days with surprisingly few births
A short list of dates consistently underperforms the calendar. A detailed reanalysis of two decades of NCHS data found that Christmas Day and New Year's Day rank among the least common US birthdays, along with the days around them.4 The Fourth of July and the days around Thanksgiving dip in a similar way, since hospitals plan around them.
February 29: the rarest birthday of all
February 29 only exists in leap years, so anyone born on that date, sometimes called a leapling, only gets a true anniversary of their birthday about once every four years.5 Do the arithmetic on four years of 365 or 366 days and the odds of landing on February 29 work out to roughly 1 in 1,461, which is why it sits at the very bottom of the rarity ranking.6
The weekday effect nobody expects
Birth dates are not spread evenly across the week either. Scheduled deliveries cluster on ordinary weekdays, quietly pulling counts down on Saturdays and Sundays, and reporting on the same holiday dip found hospital scheduling, not chance, explains much of it.7 The calculator scores each date independently of the weekday it falls on, so it will not catch this directly, but it is one more reason a date can run lower than its month suggests.
Cesarean deliveries push the pattern further
About one in three US births is delivered by cesarean section, a share that has held steady for years.8 Since most cesareans and induced labors are planned in advance, hospitals rarely book them for a Saturday, Sunday, or major holiday, which pushes those dates near the bottom of the rarity ranking.
The September peak isn't just an American pattern
The late summer surge is not unique to the United States. Official birth records in England and Wales show the same late September cluster, with the least common dates bunched around Christmas and New Year, mirroring the US pattern almost exactly.9 Different countries, same nine month arithmetic.
What this means for your birthday speech
Your birth date is free material for a speech, and its rarity decides the direction to take. A common September date invites a joke about sharing a birthday with what feels like half the country, then a pivot to what actually makes this person one of a kind. A rare date, especially February 29, Christmas, or New Year's, barely needs a setup line, since the date does the work for you. For a full speech built around that story rather than just an opening line, our birthday speech generator turns a short questionnaire about the birthday person into a finished, personal speech in about fifteen minutes. For the rest of the speech once you have your opening, see our guide on how to give a birthday speech.
Conclusion
How rare your birthday is comes down to two things: whether it falls in the September peak or a quieter month, and whether it lands on a holiday like Christmas, New Year, or Leap Day that hospitals plan around. February 29 sits alone at the bottom of the ranking, a real birthday that only shows up once every four years, while a run of mid September dates sits at the top, shared by more people than almost any other stretch of the calendar.
For a birthday speech, that ranking is more than trivia. A common date gives you a lighthearted, relatable opening. A rare one gives you a story that barely needs an introduction.
Sources
- CDC National Center for Health Statistics(ncbi.nlm.nih.gov)
- AgeFinder(agefinder.org)
- The Daily Viz(thedailyviz.com)
- The Daily Viz(thedailyviz.com)
- Wikipedia(wikipedia.org)
- Entertainment Now(entertainmentnow.com)
- FiveThirtyEight, via ABC7 New York(abc7ny.com)
- Wikipedia(wikipedia.org)
- UK Office for National Statistics(ons.gov.uk)
Frequently Asked Questions
What is the most common birthday in the United States?
Analyses of decades of US birth records consistently point to mid September as the most common stretch of birthdays, with September 9 and September 19 repeatedly showing up among the single most common dates. The pattern lines up with a conception window around the winter holidays roughly nine months earlier.
What is the rarest birthday in the United States?
February 29 is the rarest birthday by far because it only exists in leap years, about once every four years. Among birthdays that occur every year, December 25 and January 1 are consistently the least common, since hospitals schedule far fewer planned deliveries around those holidays.
How does the birthday rarity calculator work?
The calculator applies real seasonal birth patterns from US data to every day of the year, using a monthly weighting plus specific adjustments for dates like Christmas, New Year, the Fourth of July, and Leap Day, where planned births are routinely shifted. It then estimates how your date compares to the average day and gives it a rank out of 366.
Why are fewer babies born on weekends and holidays?
A large share of US deliveries are cesarean sections or induced labors that hospitals schedule in advance, and staff mostly book those procedures on weekdays outside of major holidays. That pushes the birth count down on Saturdays, Sundays, Christmas, New Year and other holidays, and up on an ordinary Tuesday or Wednesday.