# Can You Guess How Many Living People Share Your Birthday?

When people add "And many more..." to the end of "Happy Birthday," they aren't kidding.

Ruth Black/Shutterstock

Off the top of your head, can you think of someone you know who has the same birthday as you? On your own birthday, have you found yourself sending well-wishes to multiple Facebook friends? We bet you’ve asked Google what famous people share your birthday. One thing’s for sure: while your birthday is your special day, you are far from the only one.

So how many living “birthday buddies” do you have throughout the entire world? Well, it’s impossible to know an exact number. Thousands of people die and are born every single day, so that number is constantly changing anyway. But there’s a way to find an average, and it couldn’t be easier. The world’s current population is about 7.6 billion, so, dividing that number by the number of potential birthdays, 365, gives us a reasonable estimate as to the number of people born on the same day as you. And fun fact: October babies are more likely to live until 100!

Keep in mind that this is the number of people who celebrate their birthday on the same day of the year as you, not the number of people born the exact same day (in the same year) as you. That would be a much smaller number (but still pretty giant).

So, what’s the verdict? The number of people with the same date of birth as you is somewhere around 20.8 million. Yes, you share your big day with millions of people. Getting a little more specific, there are about 885,000 Americans with the same birthday as you. In the most populous country in the world, China, you have about 3.8 million birthday buddies. In the smallest country in the world, however, it’s only a meager two or three!

Of course, some birthdays are more common than others. Nine of the top 10 of them, in fact, are in the same month! So if your birthday is September 9, the number is probably a little above average. If you were born on Christmas or New Year’s Day, it’s probably somewhat smaller. And February 29 is another matter entirely.

Don’t worry, we didn’t forget about the leap day! Yes, there are technically 366, not 365, potential birthdays. But since February 29 doesn’t occur every year, dividing the world population by 366 would skew the average. If you were born on this day, you share your birthday with about 5.2 million people. This is 1/1461 of 7.6 billion (1461 is the number of days in four years, leap day included.) By the way, here’s when the next leap year is.

Now that you know how many other people to sing “Happy Birthday” to, learn about the fascinating origin of the birthday cake.

[Sources: ThoughtCo, OMGfacts.com]

Meghan Jones is a word nerd who has been writing for RD.com since 2017. You can find her byline on pieces about grammar, fun facts, the meanings of various head-scratching words and phrases, and more. Meghan graduated from Marist College with a Bachelor of Arts in English in 2017; her creative nonfiction piece “Anticipation” was published in the Spring 2017 issue of Angles literary magazine.