Birthday Statistics
📊 Birthday Statistics
Some birthdays are common, some are rare, and there is surprising math hidden in them. Here are the facts — based on real birth statistics and mathematics, not fortune-telling.
Birthday Rarity
How common is your birthday among all 366 days? Check it against real birth statistics.
Open →Birthday Paradox
In just 23 people, ~50% chance two share a birthday? Explore the famous math.
Open →🔼 Most common birthdays
- 1 September 12 ~12,735/yr
- 2 September 19 ~12,696/yr
- 3 September 20 ~12,542/yr
- 4 December 19 ~12,446/yr
- 5 September 10 ~12,445/yr
🔽 Rarest birthdays
- #366 February 29 ~2,791/yr
- #365 December 25 ~6,438/yr
- #364 January 1 ~7,735/yr
- #363 December 24 ~8,034/yr
- #362 July 4 ~8,815/yr
📈 See the full rank of all 366 days →
What your birthday profile shows
Enter your birthday to also see, for your exact date:
- Your birth-month trend (high / low season)
- How many people share your birthday (Japan & world)
- This date's rarity (rank out of 366)
- World population when you were born → now
About the data
Birthday rarity uses real US birth statistics (SSA, 2000–2014, published by FiveThirtyEight) over all 366 days; the birthday paradox is an exact formula; world population uses World Bank data; birth-month trends use Japan’s MHLW vital statistics. None of this is fortune-telling, and we never invent scores or labels.
※ Figures differ by country and year. About our data