Birthday season for a jewelry brand means one thing on repeat: someone is shopping for a birthstone piece, a new-baby name necklace, or a gift tied to a specific month. So we pulled the actual government data behind a question that gets asked constantly and answered casually even more often: which birth month really has the most babies in it? The short answer is August. The fuller answer — once you adjust for the fact that months don't all have the same number of days, and check whether it holds true state by state — is more interesting than the one-word version.
Every number below comes from the CDC's National Center for Health Statistics (NCHS), either the finalized 2023 natality report or its state-and-national provisional birth-count dataset, both pulled directly for this piece. Nothing here is estimated or rounded from a blog post repeating someone else's number.
Which Month Has the Most Babies?
In 2023 — the most recent year with finalized CDC data — the United States recorded 3,596,017 births, down 2% from 2022's 3,667,758. Broken out by month, births weren't close to evenly spread across the calendar. August led every other month, with roughly 322,000 births; February trailed the field with about 271,000, though February is also the shortest month, which matters for the next section.
Raw Counts Can Mislead — Adjusting for the Length of the Month
A raw monthly total quietly bakes in a flaw: February has three fewer days than most other months, so of course its total looks low even if a typical February day is perfectly average. Dividing each month's births by its number of days gives a fairer, per-day rate — and it changes the picture. August still leads, at roughly 10,387 births per day. But the last-place month is no longer February (9,679 births/day, actually mid-pack once adjusted) — it's April, at about 9,300 births/day, the true low point of the year on a like-for-like basis.
Does August's Lead Hold Up State by State?
A single national total can hide a lot of regional variation, so we pulled CDC's state-level monthly counts for all 50 states, Washington D.C., and Puerto Rico and checked which month was each one's individual peak in 2023. August won in 35 of the 52 — a clear majority, though nowhere near unanimous. July was the busiest month in 9, June in 3, May in 2, and September, October, and January each led in exactly one.
The outliers are worth naming: Florida's busiest month was October, not August. Hawaii peaked in January. Alaska's high point was September. Four upper-Midwest and mountain-region states — Nebraska, North and South Dakota, and Wyoming, along with West Virginia — all peaked in June instead. There's no single explanation that covers all five; climate, regional demographics, and even hospital-staffing patterns can all shift a state's calendar independently of the national trend.
Why More September Birthdays?
Zoom in from birth month to individual birthday and the pattern sharpens further. A widely cited analysis by data journalist Matt Stiles (The Daily Viz / FiveThirtyEight), built on CDC and Social Security Administration birth-date data from 1994–2014, found that 9 of the 10 most common individual birthdates in the U.S. fall between September 9 and September 20. An earlier Harvard analysis of 1973–1999 data pointed to a slightly different peak date, September 16 — different periods, same season. Neither study has published numbers as recent as our 2023 CDC monthly figures above, so treat the exact date as an approximation rather than a fixed fact, but the late-summer pattern itself shows up consistently across every dataset we could find, decades apart.
The most common explanation researchers point to is simple arithmetic: a full-term pregnancy runs about 38 weeks, and September 9–20 lands roughly 38 weeks after the December holidays — when couples spend more time together indoors during colder weather. It's a plausible pattern, not a proven single cause, and it doesn't explain why specific individual dates like December 25 and July 4 are unusually rare — that effect is generally attributed to hospitals avoiding scheduled inductions and C-sections on major holidays, which is a separate mechanism from the September conception-season pattern.
What This Means If You're Shopping by Birth Month
None of this changes what a birthstone or a name means — it just means late-summer birth months keep a lot of jewelers busy. A few of the birthstone guides we cover most often line up with the months above:
• August (the single most common birth month): peridot and spinel — a warm, olive-green stone that fits the late-summer theme it's named for.
• September (the most common cluster of individual birthdays): sapphire — corundum in every color except red, and September's official birthstone.
• July (the #2 month by raw total): ruby — corundum's red variety, and one of the most requested stones for a personalized piece.
• April (the true day-adjusted low point): diamond — the rarest birth month gets the hardest natural stone, which is a coincidence, not a design.
If you don't know a birth month's stone off the top of your head, our birthstone finder looks it up in one click — useful whether you're buying for someone born in the statistically busiest month of the year or the quietest one.
Frequently Asked Questions
What is the most common birth month in the U.S.?
August, based on 2023 CDC data — about 322,000 births, roughly 10,387 per day once adjusted for the month's length. It's also each state's individual busiest month more often than any other, topping the list in 35 of 50 states, D.C., and Puerto Rico.
What is the least common birth month?
It depends on how you measure it. By raw total, February has the fewest births — but that's largely because it's the shortest month. Adjusted for day count, April has the lowest births-per-day rate in the 2023 CDC data, at roughly 9,300 per day.
Is September 9 really the single most common birthday?
It's the most frequently cited answer, from a Matt Stiles/FiveThirtyEight analysis of 1994–2014 CDC and SSA data showing 9 of the top 10 most common birthdates fall between September 9 and 20. A separate Harvard analysis of 1973–1999 data pointed to September 16 instead. The exact date shifts slightly by dataset and period; the early-to-mid-September window is the consistent part.
Why are more babies born in late summer?
The leading explanation is timing: a 38-week pregnancy that starts around the December holidays lands in early-to-mid September. It's a widely observed correlation across decades of data, not something researchers have pinned to one proven cause.
Does birth month affect what jewelry people buy?
Indirectly, yes — birthstone jewelry and birth-month gifts are a steady category for us year-round, and late-summer months (which is also when a lot of babies are born) tend to bring a seasonal bump in birthstone and new-baby name-necklace orders alike.
