About Birthday Math
Every birthday is shared by around 22 million people worldwide. Birthday Math is a place for them: what makes your date special, what people born on it are really like, told by the people who know them, and soon, simple tools to keep track of every birthday in your life. We're just getting started.
Last updated September 29, 2026
Your birthday, all on one page
Pick your date and you'll find the things you'd actually want to know about it. How rare it is, who famous was born on it, what happened on it over the years, and when your next half birthday comes around. Every one of the 366 birthdays gets its own page, and yes, February 29 is in there too.
Made with the people who share it
The best part of a birthday is the people. So on every date page you can tell us about someone you know who was born on it: are they a night owl or an early bird, chatty or quiet? Put enough answers together and you start to see what people born on each day are like, told by the ones who know them best. It's the first step towards a place where people who share a birthday can find each other.
What's coming
This is just the beginning, and we're excited about what's next. We're working on a way to keep all the birthdays in your life in one place, so you never miss one that matters. And we're giving the stars you love their own birthday pages, packed with fun facts about their big day. We can't wait to show you.
Numbers you can trust
When we say a birthday is common or rare, it's backed by official birth records from 21 countries, from Japan to Brazil, not guesswork. You can see every birthday ranked and download the data. Famous birthdays come from Wikipedia and are ranked by who people are reading about right now, so the lists stay fresh. Photos are shared under free licenses and credited on our photo credits page. And if you ever spot something wrong, we'll fix it.