How Facebook updated 'six degrees of separation' (it's now 3.57)
If you pick any two Facebook users, it's been calculated there's an average of 3.57 "degrees of separation" between them.
The maths has been done using the social media giant's handy data set of 1.6 billion people.
Facebook wanted to test the age-old "six degrees of separation" theory to mark its 12th birthday.
"This is a significant reflection of how closely connected the world has become," the firm says.
"When people connect, powerful things happen and lives are changed.
"We see this on Facebook every day, whether it's an exchange with an old friend that brings a smile to your face or a new connection that changes your life path, or even the world."
It means that each person in the world (at least among the 1.59 billion people active on Facebook) is connected to every other person by an average of three and a half other people.
"Six degrees of separation" is where you pick a random person and connect yourself to them through other people, in six steps.
The theory had become something of an urban myth but Facebook's research shows it might actually have been too generous.
Although it's important to remember the 3.57 average is based on people with Facebook profiles, not everyone on Earth.
Mark Zuckerberg says he's targeting five billion users by 2030 so the average may well shift again.
How do I see my score?
Users logging on to the social network this week will see a video about themselves and their friends - with more prominence for the people you interact with most.
"We figured that rather than having this birthday that focuses on us, we should make sure that the world focus on what's important that's actually happening," says Zuckerberg about why he created a special "Friends Day".
He added that the stories of "how people are connecting around the world" are "amazing and inspiring to hear".
Facebook Messenger has also introduced two new sets of stickers called "Best Friends" and "Friendship" that can be downloaded free and used in conversations.
Mr Zuckerberg, along with fellow Facebook executive Sheryl Sandberg held a Friends Day event at the company's Menlo Park headquarters in California, hosting Facebook users with "extraordinary" stories of friendship.
The group included GirlCrew, a Facebook group originally created in Dublin, which empowers women to find friends and organise events in their area.
There are now 22,000 people in GirlCrew Facebook groups in more than 40 cities worldwide.