September in the birth records
September accounts for 5,399,592 births, or 8.68% of the 62,187,024 records in the SSA 2000–2014 sample. Within this month, September 12 is the most common date, ranked #1 nationally. September 1 has the fewest total records and ranks #305. The table above includes all 30 dates, not just those two extremes.
What makes this month worth a closer look
September contains the top-ranked birthday in this particular source: September 12. September 19 and September 20 also appear near the common end of the calendar. Those rankings come from adding the SSA records from 2000 through 2014, rather than importing an ordering from another birthday website.
You may have seen September 9 described as the most common birthday elsewhere. A different source, period or treatment of dates can produce a different leader. That is not a reason to swap the source’s numbers until they match a familiar headline. September 9 has its own row here, so you can make the comparison directly and keep the source attached when you share it.
Read your row and make a card
Rank #1 is most common across all 366 dates. “1 in” divides all birth records by the records for that specific date; the daily-average column divides by the number of times the date occurred. A higher “rarer than” percentage means more other dates had higher counts. These are different ways of describing the same historical sample, not estimates of everyone alive today.
Select your date in the table to open the birthday calculator. Save a portrait or landscape result, or combine it with your name. The complete methodology and original FiveThirtyEight source stay available for anyone who wants to check the numbers.