Is Six Degrees of Separation Real?
You've probably heard the claim: any two people on Earth are connected through a chain of about six acquaintances. It sounds like a party trick, but it's a real question in network science — one that's been tested, measured, and argued over for nearly a century.
The calculator above turns that idea into a personal number: how many of the world's roughly 8.2 billion people are, in theory, within six handshakes of you. The short answer to whether six degrees is real is the math checks out, but finding the actual path is a different problem entirely.
Below, we walk through why six steps is enough to cover a planet this size, what Stanley Milgram's famous letter experiment really found, and what Facebook's own data showed when it checked the claim on more than a billion users.
The arithmetic of a small world
Here's why six degrees isn't as far-fetched as it sounds. Anthropologist Robin Dunbar's research suggests a typical person maintains meaningful relationships with about 150 people — now known as Dunbar's number. If you know 150 people, and each of them knows 150 different people, and so on, your reach grows exponentially with every step outward.
Multiply it out: 150 × 150 × 150 × 150 × 150 × 150 equals 150⁶, or about 11.4 trillion possible six-step paths. That's roughly 1,400 times the entire population of Earth, about 8.2 billion people. Even accounting for the fact that real social circles overlap heavily — your friends mostly know each other, not 150 total strangers apiece — there's enormous mathematical slack. Six steps doesn't just barely cover the planet; on paper, it covers it many times over.
How the calculator works
The number above is built from two figures: the current world population, about 8.23 billion people, and the small-world arithmetic described above — 150 relationships per person, raised to the sixth power, for roughly 11.39 trillion theoretical six-step paths.
This is a ceiling, not a guarantee. It shows how many connection-paths could exist if everyone's 150 relationships were entirely unique strangers with zero overlap. In reality, your coworkers know each other, your family overlaps with your hometown friends, and whole groups share the same 150 people many times over. That redundancy shrinks your true unique reach well below 11.4 trillion.
What the estimate captures honestly is the gap between the two numbers: even after heavy overlap, the theoretical paths available at six steps still dwarf the number of humans alive. That's the mathematical case for six degrees — actually finding the path is a separate, harder problem covered in the FAQ below.
Frequently asked questions
What is six degrees of separation?
Six degrees of separation is the idea that any two people on Earth can be connected through a chain of no more than about six mutual acquaintances. The concept traces back to Hungarian writer Frigyes Karinthy, who proposed it in a 1929 short story, and it became widely known after psychologist Stanley Milgram's 1960s small-world experiment, which tested how many steps it took a letter to reach a stranger.
Is six degrees of separation scientifically true?
Partly. Milgram's original experiment found a median of about six steps among the letter chains that were completed — but most chains never finished, so the result rests on a fraction of the data. Modern network science, studying huge digital datasets like Facebook and Twitter, broadly supports that short paths exist between almost anyone. The small-world effect looks real; Milgram's exact number was more suggestive than definitive.
What's the 150^6 arithmetic behind six degrees?
If each person maintains about 150 relationships (see Dunbar's number below), six steps out multiplies to 150 raised to the sixth power: 150 × 150 × 150 × 150 × 150 × 150, which equals about 11.39 trillion possible six-step paths. That's roughly 1,400 times the world's population of about 8.2 billion, which is why six steps is, mathematically, more than enough distance to connect any two people on the planet.
What did Facebook find about degrees of separation?
In 2016, Facebook's research team measured the average distance between its roughly 1.6 billion active users and found it was 3.57 intermediaries — most pairs of users were connected through about 3.5 mutual friends, shorter than Milgram's six. That's likely because a global social network with no geographic barriers makes finding short paths far easier than mailing physical letters in the 1960s.
What is Dunbar's number?
Dunbar's number is about 150 — the number of stable social relationships anthropologist Robin Dunbar proposed a person can realistically maintain, based on research linking primate brain size to social group size. Dunbar also described smaller layers within that 150: roughly 5 close intimates, 15 good friends, and 50 broader friends, with 150 as the outer limit of meaningful, ongoing relationships.
Does social media shrink degrees of separation?
The evidence suggests yes, at least among people who use the same platform. Facebook's 2016 study found its measured degrees of separation had fallen from an earlier estimate of about 4.7 (from a 2011 study) to 3.57, as the platform grew and connected more of the world. Digital networks remove geographic and social barriers that made Milgram's postal chains slow and prone to breaking, so measured distances tend to shrink as platforms grow.
Can I actually reach anyone in six steps?
Statistically, the paths almost certainly exist — the arithmetic above shows a huge surplus of possible routes. Practically, finding one is the hard part: in Milgram's experiment, most letter chains stalled out before reaching the target, because people didn't know who in their network was the best next link. Six degrees describes what's mathematically possible, not a guaranteed shortcut you can navigate on demand.
Sources
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