birthday odds .

What day of the month has the most births?

The 20th had the highest daily average in U.S. SSA birth records from 2000 to 2014. See all 31 numbered days and why the answer changes with the method.

Reviewed

In U.S. Social Security Administration birth records from 2000 through 2014, the 20th comes first: 11,574 births per actual 20th. The 21st is close at 11,551. This answer describes those historical records; it cannot identify a winning numbered day for babies born today.

How does every numbered day compare?

The table pools every January 1st, February 1st, and so on, then divides by the number of actual dates in each group. Rank 1 has the highest average births per date.

Average recorded births for each numbered day across actual calendar dates. U.S. SSA records, 2000–2014.
Day of monthRecorded birthsActual daysAverage births per dayRank by average
12,003,62718011,13126
22,030,44718011,28023
32,042,44118011,34719
42,004,78518011,13825
52,036,18518011,31221
62,037,72918011,32120
72,063,41618011,46310
82,061,65218011,45411
92,044,60018011,35917
102,066,15418011,4798
112,054,09818011,41213
122,072,48318011,5145
132,000,06418011,11128
142,076,29118011,5354
152,066,99918011,4837
162,058,65118011,43712
172,071,57218011,5096
182,077,67318011,5433
192,065,32818011,4749
202,083,24718011,5741
212,079,19818011,5512
222,051,01218011,39515
232,023,55518011,24224
241,993,20318011,07330
251,972,53418010,95931
262,001,31118011,11827
272,035,48318011,30822
282,051,52818011,39714
291,918,96516911,35518
301,879,92516511,39316
311,162,86810511,07529

The denominator matters for the 31st. It appeared 105 times, while each day numbered 1 through 28 appeared 180 times. Sorting total births alone would penalize the 31st for having fewer dates. It averaged 11,075 births per appearance. The 25th had the lowest average, 10,959.

How stable is first place?

The 20th leads in just 1 of the 15 individual SSA years. Its lead over the 21st in the combined records is small, and a different comparison picks a different day.

For a closer check, we compared every date with other dates on the same weekday in its month and year. By that measure, the 18th leads, averaging 2.5% above its matched weekday mean. The 20th averages 2.0% above its own matched mean. This comparison accounts for the mix of weekdays and months; it does not tell us why births occurred on particular dates. Our weekday study shows how much daily counts differ between weekdays and weekends.

The earlier CDC/NCHS records give another useful check. From 1994 through 1999, the 22nd has the highest average, at 10,942 births per actual date. That period uses a different source system as well as different years, so the change in first place is not evidence of a time trend.

Does Christmas affect the 25th?

December 25 is included in the 25th's average. We reran the ranking without January 1, July 4, December 24, December 25, and December 31. The 13th then had the lowest average. This check shows that selected fixed dates matter to the bottom ranking; it cannot tell us what would have happened without those holidays.

Source and method

We counted 62,187,024 recorded U.S. births across 5,479 actual dates in the SSA daily birth file. For each number from 1 through 31, we added births across months and years and divided by its number of actual appearances. February 29 contributes only in leap years; seven months have a 31st.

For the earlier comparison, we used only 1994–1999 rows from the CDC/NCHS file. Its overlapping 2000–2003 rows were excluded. These records describe historical U.S. births, rather than worldwide births or the birthdays of everyone alive today. The methodology explains the site's data sources and ranking measures.

If you want to compare a specific month and date, use the full birthday ranking or check your birthday against the longer historical baseline.