How rare is a February 29 birthday, really?
February 29 accounts for 0.0613% of recorded births, or about 1 in 1,631, in the U.S. data used by Birthday Odds. The records contain 52,561 leap-day births out of 85,712,738 births from 1994 through 2014.
It has the fewest total births of all 366 birthday dates. But February 29 appeared only 5 times during those 21 years: 1996, 2000, 2004, 2008, and 2012. Every other month/day appeared 21 times.
What changes when you count births per occurrence?
Divide the 52,561 leap-day births by those 5 actual February 29 dates. That gives an average of 10,512.2 births each time the date occurred.
| Birthday | Recorded births | Occurrences | Births per occurrence |
|---|---|---|---|
| February 29 | 52,561 | 5 | 10,512.2 |
| December 25 | 138,628 | 21 | 6,601.3 |
| January 1 | 164,362 | 21 | 7,826.8 |
On that measure, February 29 moves from rank #366 to #347 out of 366, where #1 means the most births. 19 dates have a lower average per occurrence. Leap day is still near the rare end of the ranking.
Total births tell you how often February 29 appears among the recorded birthdays. The per-occurrence average answers a different question: how many births happened on the date when it existed? Its share of all recorded births stays at 0.0613%.
Why do people say the odds are 1 in 1,461?
A simple four-year cycle has 365 + 365 + 365 + 366 = 1,461 days, including one February 29. If every day had the same number of births, leap day would account for 1 in 1,461 births over that cycle.
That calculation assumes equally frequent births across a four-year cycle. Our records span 21 years, and birth counts vary across days and years. The Gregorian calendar also skips some century leap years: a century year must be divisible by 400 to qualify. The U.S. Naval Observatory explains the leap-year rule.
Compare leap day with your birthday
In the ranking above, choose "Births per occurrence" to compare the average for each date. Excluding February 29 answers another useful question: which birthday is rarest among dates that occur every year?
You can also check February 29 directly or explore birth counts around selected holidays.
Sources and limits for this comparison
The counts come from FiveThirtyEight's historical U.S. birth files: CDC/NCHS for 1994 through 1999 and SSA for 2000 through 2014. The methodology explains source overlap and the calculations.
Dividing by occurrences adjusts for how often the date appears. It does not adjust for which weekdays or years those five leap days fell in. These historical records describe the births counted in this dataset; they do not estimate the birthdays of everyone alive today or a particular baby's chance of arriving on leap day.