Every birth month, ranked
You will hear both August and September named as the most common birth month. That is because some count a month's total births and others count births per day. We count per day, so a 31-day month does not win just for being long.
September has the most births per day
About 11,448 a day in the United States: the month's births divided by its 30 days.
Three months that mislead
Why September
Count back thirty-eight weeks from September 9, the most common birthday of all, and you land on December 17: the week of the winter holidays.
- Why that week. It is the one stretch of the year when most people are off work together, celebrating, and in much of the country it is cold enough to stay in.
- A slope, not a spike. Those conceptions spread across the weeks either side of the holidays, so the births spread too: up through late August, over the top in mid-September, down through October.
- The other end. Christmas, New Year's Day and the Fourth of July are the days hospitals postpone every delivery they can. That gives December the rarest birthday, and January the fewest births per day.
27 countries, twelve months each
The most births per day come in September in 15 of the 27 countries, July in 8 and March in 3. Ecuador peaks in May. The fewest come in December, in 16 of them, and March, in 3 of them.
RarestMost common
Learn more about each month
Quick answers
What is the most common birth month?
September, with about 11,448 births per day in the United States (+5.6% against the average for the year); 15 of the twenty most common birthdays fall in it. Counted by total births, August comes first, because it has 31 days.
What is the least common birth month?
January, with about 10,394 births per day, โ4.2% against the average for the year. February has the fewest births in total because it is the shortest month; per day it is the 5th rarest of the twelve.
Why is September the most common birth month?
Because of when people conceive. Thirty-eight weeks before Septemberย 9, the most common birthday of all, is Decemberย 17: the winter holidays. The peak is a slope through the middle of September, not a single day.
Is February the rarest month to be born in?
Only if you count totals, and then only because it is short. Per day, February is the 5th rarest of the twelve; January is quieter. Leap day does not change that: Februaryย 29 is counted on the years it happens.
Is the most common birth month the same in every country?
No. The most births per day come in September in 15 of the 27 countries, July in 8 and March in 3. Ecuador peaks in May. The fewest come in December, in 16 of them, and March, in 3 of them. The United States and Malaysia bottom out in January; Belgium and Hungary in November; Chile in May; Costa Rica in February; Mexico in April; and New Zealand in June.