The Most Common Birthday in the US: September 9

What is the most common birthday in the United States? Based on registered births compiled from CDC and Social Security data covering 1994 to 2014, more babies were born on September 9 than on any other date, and nine of the ten most common birthdays fall between September 9 and September 20.

Birthdays are not spread evenly across the calendar. Some dates get crowded out year after year, others barely show up at all, largely because of conception timing and hospital scheduling.

This page collects the key statistics behind how birthdays are distributed in the United States: which month leads, which single date wins, and why the day of the week matters more than most people assume.

Whenever I sit down to help someone write a birthday speech, the date is usually the first thing I ask about. If the guest of honor was born in mid September, they share their birthday with more Americans than almost anyone else, which is a fun, relatable line to open with. If they were born on February 29 or on a major holiday, the story practically writes itself. Either way, the calendar gives you a free first sentence.

Grace Whitfield

1. September 9 is the single most common birthday in the US

Analysis of U.S. birth records from 1994 to 2014, drawn from the CDC's National Center for Health Statistics and the Social Security Administration, found an average of about 12,301 babies born on September 9 each year, more than on any other date on the calendar.¹

2. Nine of the top ten birthdays fall in a narrow September window

The most common birthdays cluster tightly between September 9 and September 20, with September 19 and September 12 rounding out the top three. Only one date outside that stretch, July 7, makes the top ten.²

3. The cluster lines up with conceptions around Christmas and New Year's

Counting back roughly 38 weeks from mid September points straight at the winter holidays. Writers who cover the pattern link it to extra free time and togetherness during the holidays turning into a conception bump nine months later.³

4. Ranked by month, August edges out September

The single busiest birthday is in September, but the busiest overall birth month is actually August. A review of CDC WONDER natality data covering 2016 through 2023 found August is the most common birth month in 45 of the 50 states, with September a close second nationally.⁴

5. The US recorded 3,628,934 births in 2024

According to final NCHS data, 3,628,934 births were registered in the United States in 2024, a 1 percent increase over 2023. The general fertility rate still declined slightly, to 53.8 births per 1,000 women aged 15 to 44.⁵

6. Around 9,800 babies are born in the US every day

Spreading the annual total evenly across the calendar works out to roughly 9,800 births per day, based on 2023 CDC figures. Real daily counts swing far wider, from well over 12,000 on a busy September weekday to under 7,000 around Christmas.⁶

7. Tuesday is the most common day of the week to be born

Births are not spread evenly across the week either. Tuesday consistently ranks as the most common day of the week for U.S. births, while weekends fall well below the weekday average.⁷

8. About one in three US births is a cesarean delivery

The cesarean delivery rate rose to 32.3 percent of all U.S. births in 2023. Because a large share of cesareans are scheduled in advance, units plan very few for Saturdays, Sundays, or major holidays, which pushes the pattern even further.⁸

9. Labor induction reinforces the weekday effect

Beyond scheduled cesareans, induced labor is also concentrated on weekdays. Doctors control the timing of induced deliveries, and hospitals staff obstetric units more thinly on weekends and holidays, so fewer inductions get booked for those days.⁹

10. December 25 is the least common birthday of the year

Christmas Day sits at the very bottom of the ranking, with an average of roughly 6,574 US births, well under half of the September 9 count. Hospitals rarely schedule elective deliveries on the day itself.¹⁰

11. New Year's Day, Christmas Eve, and July 4 round out the quietest dates

After December 25, the next least common birthdays are January 1, December 24, and July 4. Every one of the least common dates in the country lines up with a major federal holiday, the same pattern seen around Thanksgiving.¹¹

12. Between 30 and 40 percent fewer babies are born on Christmas Day

Compared with the busiest day of the year, Christmas Day sees roughly 30 to 40 percent fewer births. Almost no cesareans are scheduled for public holidays or weekends, and doctors are reluctant to induce labor when they would rather be off with their own families.¹²

13. Friday the 13th has around 800 fewer births than expected

Statisticians who reanalyzed two decades of US birth data found roughly 800 fewer babies born on Friday the 13th than a random day would predict, an effect attributed partly to parents and even some hospital staff steering scheduled deliveries away from the date.¹³

14. Holidays suppress births even more than the 13th or a leap day

The same analysis found that major holidays like Christmas and Thanksgiving pull down birth counts by a wider margin than superstition around the 13th or the rarity of February 29, a reminder of how much scheduling now shapes the calendar.¹⁴

15. February 29 is the rarest birthday by far

Because February 29 only appears in leap years, the odds of being born on that exact date are about 1 in 1,461, compared with roughly 1 in 365 for any other day. It is by a wide margin the least common calendar date in how rare a US birthday can get.¹⁵

16. Roughly 363,000 living Americans are leaplings

Social Security Administration records cited alongside CDC data suggest about 363,000 living people in the United States were born on February 29, a tiny fraction of the population and further proof of just how uncommon the date is.¹⁶

17. Leap years follow a fixed, predictable rule

A leap year falls on every year evenly divisible by four, except century years, which qualify only if they are also divisible by 400. That is why 2000 was a leap year but 1900 and 2100 are not.¹⁷

18. The average mother is 29.6 years old at the time of birth

Across all births, the mean age of US mothers reached 29.6 years in 2023, up from 28.7 in 2016. At first birth, the average climbed to 27.5, a record high and part of a steady shift toward later childbearing.¹⁸

19. The twin birth rate sits at about 30.7 per 1,000 births

The 2023 twin birth rate was 30.7 twins per every 1,000 births, a slight decline from 2022 but still roughly double the rate from the early 1980s, a shift linked to fertility treatment and rising maternal age.¹⁹

20. The September birthday peak shows up in other countries too

The pattern is not unique to the US. In England and Wales, the Office for National Statistics found the most popular birthday clusters at the very end of September, with eight of the ten most common dates falling there. The same nine month link to Christmas conceptions, plus holidays pushing scheduled deliveries away from December, shapes both countries almost identically.²⁰

If a birthday like this is coming up and you want a speech that actually lands, our AI speech generator turns a few details about the birthday person into a finished, personal speech in about 15 minutes.

Conclusion

The most common birthday in the US is September 9, based on CDC and Social Security data spanning 1994 to 2014, with the wider mid September window explained by conceptions clustering around the winter holidays. August now narrowly leads as the busiest birth month overall in more recent CDC data, while February 29 remains the rarest date on the calendar by a wide margin, and Christmas Day the rarest ordinary one.

For a birthday speech, the date itself can be a gift. A guest of honor born in that September cluster shares their day with more people than almost anyone else in the country, and someone born on a leap day or a holiday has a story that needs almost no embellishing. Our guide on how to give a birthday speech covers the rest of the structure, and our full birthday statistics roundup has more numbers like these.

Sources

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5. National Center for Health Statistics (NIH)(pmc.ncbi.nlm.nih.gov)
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8. NCHS, Births: Final Data for 2023(ncbi.nlm.nih.gov)
9. The Conversation(theconversation.com)
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17. Wikipedia(wikipedia.org)
18. NCHS, Trends in Mean Age of Mothers(ncbi.nlm.nih.gov)
19. NCHS, Births: Final Data for 2023(ncbi.nlm.nih.gov)
20. UK Office for National Statistics(ons.gov.uk)