How common is your birthday?

The short answer

What is the most common birthday?

September 10 is the most common birthday in the United States, based on 62.2 million births from 2000–2014, and December 25 is the least common.

9 of the 10 most common birthdays fall in mid-September. The 10 least common all land on a holiday or right beside one: Christmas, New Year’s Day, the Fourth of July, Halloween, and the week of Thanksgiving. Across the year, most dates sit within a few percent of a typical day. The ranking uses a weekday-adjusted index, where 100 is a typical day.

Index: births compared with a typical day of the same weekday and year (100 = typical). The second figure is the plain average number of US births on that date each year. Data: FiveThirtyEight (CC BY 4.0), from SSA.

Every date, in order

All 366 birthdays ranked

The full birthday ranking, from the most common date to the least. Sort by date to find your own, or by average births to see the plain counts. After a lookup, your date is marked here too.

The method

How to calculate how common a birthday is

1. Start with daily birth counts. The data lists every day from January 1, 2000 to December 31, 2014: 5,479 days and 62,187,024 US births.
2. Compare each day with its own weekday. Divide the day’s births by the average for the same weekday in the same year. Far fewer births are scheduled on weekends, so without this step a date would rank higher just for landing on weekdays more often.
3. Average the ratios for each date. Every month and day has 15 ratios, one per year. February 29 has 4.
4. Turn the average into an index. Multiply by 100, so 100 is a typical day, 110 means 10% more births, and 90 means 10% fewer.
5. Rank all 366 dates. The highest index is rank 1. The percentile is 1 − (rank − 1) ÷ 365: the share of the other 365 dates that had fewer births.

Worked example

Scheduling, not luck

Why holidays have the fewest birthdays

Many US births are scheduled: labour is induced, or a C-section is planned, for a chosen day. Hospitals book fewer of those on holidays, so births on those dates drop, and some move to the days around them. That is why the least common birthdays read like a holiday calendar.

Christmas Day

December 25: ranks 366th, 40.9% fewer births than a typical day

New Year’s Day

January 1: ranks 365th, 27.6% fewer births than a typical day

Christmas Eve

December 24: ranks 364th, 27.5% fewer births than a typical day

Independence Day

July 4: ranks 363rd, 22.4% fewer births than a typical day

Day after Christmas

December 26: ranks 362nd, 14.8% fewer births than a typical day

Day after New Year’s Day

January 2: ranks 361st, 14.3% fewer births than a typical dayStill inside the holiday break. Its low count most likely reflects the same holiday scheduling of inductions and planned C-sections.

Halloween

October 31: ranks 360th, 11.3% fewer births than a typical dayNot a public holiday, yet births ran below a typical day in all 15 years. Fewer scheduled inductions and C-sections are the likely reason; the data cannot say why they are booked less.

Thanksgiving window

November 22–28: ranks 348th to 359thThanksgiving falls on one of these seven dates each year, so each carries part of the holiday dip in scheduled inductions and C-sections.

Why so many September birthdays?

Counting back about 39 weeks from mid-September lands in late December, and in this data births climb through July and August and peak in September. A common explanation is conception around the winter holidays, but the data records only when babies were born, not why, so this page does not claim a cause.

A leap-day birthday

February 29 exists in one year in four, about once every 1,461 days, so it has only 4 data points here (2000, 2004, 2008, and 2012). Its rank compares an average leap day with other dates, one occurrence each; as a birthday it is far rarer than any other date.

Numbers people choose

Do number-pattern dates like 9/9/09 get more births?

In this data, they did. From 7/7/07 to 12/12/12, each repeating date had 17% to 21% more births than a typical day of the same weekday that year. 6/6/06 went the other way, with 14.5% fewer. Because many births are scheduled, the pattern is consistent with some parents and doctors choosing these dates, and avoiding 6/6/06, though the data cannot show anyone’s reasons.

1. 1/1/01Monday · 7,663 birthsIndex 67.0 · New Year’s Day
2. 2/2/02Saturday · 9,021 birthsIndex 103.6
3. 3/3/03Monday · 12,774 birthsIndex 107.0
4. 4/4/04Sunday · 7,559 birthsIndex 99.3
5. 5/5/05Thursday · 14,357 birthsIndex 108.3
6. 6/6/06Tuesday · 11,661 birthsIndex 85.5
7. 7/7/07Saturday · 10,499 birthsIndex 117.6
8. 8/8/08Friday · 15,374 birthsIndex 117.2
9. 9/9/09Wednesday · 16,081 birthsIndex 121.3
10. 10/10/10Sunday · 8,490 birthsIndex 118.2
11. 11/11/11Friday · 14,392 birthsIndex 117.9
12. 12/12/12Wednesday · 14,667 birthsIndex 118.2

Seeing repeating numbers everywhere is a different question, about attention and meaning. Our guide to why you might keep seeing angel numbers looks at both.

The birthday problem

How many people does it take to share a birthday?

Fewer than most people guess. In a group of 23, the chance that at least two people share a birthday is just over 50%. The figures below assume every one of 365 birthdays is equally likely and ignore February 29. As the ranking above shows, real birthdays are not spread evenly, which nudges the true chance slightly higher.

Reading it well

What a birthday’s rank can and cannot tell you

A rank tells you how many babies were born on a date in the United States from 2000–2014, compared with the other 365 dates. It is a fact about hospital calendars and families’ plans, not about the people born on that day. A rare birthday is not a sign, and a common one is not ordinary in any way that matters.

If you came here through numerology, the birth date works differently there: its digits, year included, are reduced to your Life Path number, and your day of birth gives the Birthday number in the complete numerology calculator. Both are symbolic conventions, not measurements. And if your birthday keeps catching your eye on clocks and receipts, our guide to synchronicity is a good next read.