Birthday Math
★ Built on 85.7 million real birthdays

Everything about your birthday, on one page

Your half birthday, your golden birthday, the day of the week you were born and how many people share your big day. Pick a date and we'll make you a birthday page to keep or send to someone.

Or peek at today, September 28 September 9 December 25 February 29

JanFebMarAprMayJunJulAugSepOctNovDec
Hover a line 366 birthdays in one ring
A year of birthdays

Every birthday, in one ring

Each little line is one day, starting with January 1 at the top. The longer and pinker the line, the more babies are born that day. Tap any line to open its page.

Today, September 28

Tap any day

How crowded is your birthday?

Every square is one day of the year. Pink days are packed with birthdays, blue days are quiet. Tap one to open its page.

JanFebMarAprMayJunJulAugSepOctNovDec
Quiet PackedAverage U.S. births per day, 1994 to 2014
12,344

babies on an average September 9, the busiest birthday of the year. Count back nine months and you land on the holidays. Make of that what you will.

6,601

on Christmas Day, the quietest. Hardly anyone schedules a delivery for Christmas, and it shows.

1 in 1,461

days is a February 29. Leap-day babies are rare because the day is rare, not because it's unpopular.

Weird but true
68%

more babies are born on a Tuesday than on a Sunday

The month barely matters: September only beats January by about 10%. The day of the week matters a lot, because most planned deliveries happen Monday to Friday.

More birthday math

Little tools, big answers

Half birthday calculator

The date six months after your birthday, and what happens if you were born on August 31.

Find mine →

Golden birthdays

The year your age matches the day you were born. Coming soon.

Most common birthdays

All 366 days ranked, with the stories behind the peaks. Coming soon.