Based on birth records in the United States and broader Western data, here is how birthdays are distributed across the 12 months:
Birthday Month Rankings
| Rank | Month | % of annual births (approx.) |
|---|---|---|
| 1 | September | ~9.0% |
| 2 | August | ~8.8% |
| 3 | July | ~8.7% |
| 4 | October | ~8.6% |
| 5 | June | ~8.3% |
| 6 | November | ~8.2% |
| 7 | May | ~8.1% |
| 8 | December | ~8.0% |
| 9 | April | ~7.9% |
| 10 | March | ~7.8% |
| 11 | January | ~7.6% |
| 12 | February | ~7.3% |
Why Is September the Most Popular?
September babies are often conceived around the holiday season (December and January), a time when more couples are together and conception rates tend to rise. Studies consistently show a spike in births in late summer and early September across many countries in the Northern Hemisphere.
The data holds up across multiple decades of birth records in the US, UK, and Australia, making September the most reliably popular birth month.
Rarest Birthdays
February 29 (leap day) is the rarest birthday — it only occurs every 4 years. People born on this date are called "leaplings" and technically only have a true birthday once every four years.
Among regular dates, December 25 and January 1 are statistically rare, likely because fewer C-sections and induced labors are scheduled on major holidays. December 24 and July 4 also rank among the least common birthdays in the US.
FAQ
What is the most common birthday month?
September, with approximately 9% of all annual births.
What is the rarest birthday?
February 29 (leap day), which only exists in leap years. Among non-leap-day dates, December 25 is one of the rarest.
What month has the fewest birthdays?
February consistently has the fewest birthdays, partly due to having fewer days and partly due to lower conception rates around May.
Is there a peak season for births?
Yes. In the Northern Hemisphere, late summer (August–September) is the peak birth season.