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What Are Friends and How Many Do You Need?

I've spent half a century writing for radio and print (mostly print). I hope to still be tapping the keys as I take my last breath.

How does science define friendship? How many friends can someone really have?

How does science define friendship? How many friends can someone really have?

There’s an ongoing competition among certain people for having the highest number of Facebook friends. Justin Tayler, an Australian who lists his profession as a nightclub promoter (whatever that is), says he has 5,000 friends on Facebook.

Oxford University’s Professor Robin Dunbar would likely challenge Mr. Tayler to name 150 of his so-called friends from memory, and Mr. Tayler would probably fail miserably. There’s no way that any one person can maintain a relationship meaningful enough to constitute friendship with that many people.

The gang's all here!

The gang's all here!

What Is a Friend?

Let’s check in with Dr. Suzanne Degges-White. She is a professor and chair of the Counseling and Higher Education Department at Northern Illinois University. She writes in Psychology Today that good relationships involve mutual interactions and that “there are certain personal characteristics it’s essential to cultivate to build healthy, lasting friendships.”

She has developed a checklist of the characteristics that need to be present for a true friendship to exist. These include . . .

  • trustworthiness and the ability to trust others
  • honesty and loyalty
  • dependability
  • the ability to experience and express empathy
  • the ability to be non-judgmental
  • the ability to be a good listener
  • the ability to be supportive in good times and bad times
  • self-confidence
  • a good sense of humour
  • the ability to be fun to be around

Robin Dunbar on Group Dynamics

With those ground rules in place, let’s move on to Oxford University Professor Robin Dunbar. He’s an expert in evolutionary neuroscience, a discipline that studies changes in human behaviour over time. He has his own definition of friendship; it is “the number of people you can have a relationship with involving trust and obligation―there’s some personal history, not just names and faces.”

Dr. Dunbar and his colleagues have been looking at contemporary and historical data about group sizes. What they have found is remarkable consistency from hunter-gatherer groups to online social media; the maximum effective size is 150 individuals.

Groups that exceed the magic number of 150 start to fracture and split off into sub-groups; 150 is now known as the “Dunbar number” in the world of social science.

Dunbar's Number

Dunbar's Number

This does not mean that a person can look forward to having 150 close friends. The BBC explains that according to Dunbar’s theory “the tightest circle has just five people―loved ones. That’s followed by successive layers of 15 (good friends), 50 (friends), 150 (meaningful contacts), 500 (acquaintances), and 1,500 (people you can recognize).”

The number 150 relates to casual friends—people we might see at a large party and then bump into again at a wedding. We know them and a little bit about them, but they are not intimate friends. The different groups tend to be fluid with people going from good friends to just friends or acquaintances and vice versa.

The Social Brain Hypothesis

Dunbar and his colleagues base their theory on ideas developed in the late 1980s. Scientists have postulated that primates, including humans, developed large brains in relation to their size in order to maintain their social connections (friendships). This premise is known as the social brain hypothesis.

The Oxford University team studied the correlation of brain size to social group sizes in non-human primates. They developed the theory that the larger and more socially complex the group, the bigger the brain.

Do our large brains promote interpersonal connection?

Do our large brains promote interpersonal connection?

The Neocortex

The size of the neocortex, where high-level thinking and language reside, seems to relate closely to group size. So, according to Dunbar, “the number of individuals a person can maintain true relationships with is limited by the programming of our brain,” that’s biological anthropologist Erin Wayman writing for Smithsonian Magazine. She continues by pointing out that “even with all the supporting evidence, it’s hard to prove that primates, including humans, evolved large brains in response to the social challenges of group living.”

While we know larger brains in primates correlate to larger group sizes, we do not know if larger brains developed in response to a need for interpersonal cooperation.

While we know larger brains in primates correlate to larger group sizes, we do not know if larger brains developed in response to a need for interpersonal cooperation.

The Impact of Social Media

Of course, with social media, the Dunbar number becomes meaningless, right? Actually, it doesn’t. There are people who boast massive numbers of friends on Twitter, Facebook, Instagram, and the like, but studies show most of those relationships are very shallow.

Bruno Gonçalves and colleagues at Indiana University studied Twitter usage among 1.7 million people. The researchers report that “the data are in agreement with Dunbar’s result; users can entertain a maximum of 100–200 stable relationships.”

Michigan State University researchers found a similar result among Facebook users; the number of meaningful relationships was far fewer than the total number of “friends” on the platform.

Many "friends" on social media are just online acquaintances.

Many "friends" on social media are just online acquaintances.

Social media certainly affects our friendships but it doesn’t replace face-to-face interaction, even with video chats. Personal and physical contact is the only way to create truly close bonds.

Here’s how Maria Konnikova puts it in The New Yorker: “Without investing the face-to-face time, we lack deeper connections to them, and the time we invest in superficial relationships comes at the expense of more profound ones.”

Bonus Factoids

  • The average village size in the Doomsday Book of 1086 was―you guessed it―150.
  • By the 18th century, when parish registers in Britain gave accurate population counts, the average village still had 150 people in it.
  • Back in the day when people mailed Christmas cards to one another, the typical household had 150 people on its list in the United Kingdom.
  • The size of a company in a professional army is up to 150; this applies to the Roman Empire and the Red Army of the Soviet Union.
  • According to the BBC, “Certain organisations have taken these ideas (Dunbar’s) to heart. The Swedish Tax Authority, for instance, has restructured their offices to stay within the 150-person threshold.”


  • “Meet the Guy with the Largest Number of Facebook Friends.” Gabriel Roşu,, undated.
  • “The 13 Essential Traits of Good Friends.” Dr. Suzanne Degges-White, Psychology Today, March 23, 2015.
  • “Humans Evolved Big Brains to Be Social?” Erin Wayman, Smithsonian Magazine, October 31, 2011.
  • “Robin Dunbar: We Can only ever Have 150 Friends at Most…” Aleks Krotoski, The Guardian, March 14, 2010.
  • “Dunbar’s Number: Why We Can only Maintain 150 Relationships.” Christine Ro, BBC Future, October 9, 2019.
  • “Modeling Users’ Activity on Twitter Networks: Validation of Dunbar’s Number.” Bruno Gonçalves et al., Plos One, August 3, 2011
  • “Connection Strategies: Social Capital Implications of Facebook-Enabled Communication Practices.” Nicole B. Ellison et al, New Media and Society, January 27, 2011.
  • “The Limits of Friendship.” Maria Konnikova, New Yorker, October 7, 2014.

This content is accurate and true to the best of the author’s knowledge and is not meant to substitute for formal and individualized advice from a qualified professional.

© 2020 Rupert Taylor


Rupert Taylor (author) from Waterloo, Ontario, Canada on June 18, 2020:

Absolutely right dashingscorpio.

Ann Carr from SW England on June 18, 2020:

Yes, it's quality not quantity!

dashingscorpio from Chicago on June 18, 2020:

If you have a handful of {true friends} you're doing great!

Forget about "social media" friends. They're not (real) friends.

If you were sick they wouldn't bring you a cup of soup. Hell, most of them don't even know where you live!

A "real friend" is someone whose home address and personal phone number is in your possession. He/she is also the someone you feel you can trust to confide in when things aren't going well.

With a true friend you also have (in person gatherings) from time to time celebrating weekends, birthdays, holidays, attending each other's weddings, children's birthdays, and even funerals.

Truth be told not many of us have that much time or available heart space to give to a whole lot of people. Most people can count the number of true "ride or die" friends on (one hand).

The rest of the world consists of family, "social acquaintances", co-workers, "social media friends", and complete strangers.

Rupert Taylor (author) from Waterloo, Ontario, Canada on June 09, 2020:

Like you Ann, my circle of close friends is small. I'm a bit of an introvert and folks like me tend to have a smaller but tighter network than extroverts who gather larger numbers around them but whose relationships are shallower.

Miebakagh Fiberesima from Port Harcourt, Rivers State, NIGERIA. on June 09, 2020:

It is an interesting read and the research likewise, interesting more.

Ann Carr from SW England on June 09, 2020:

Interesting! I don't think I could get anywhere near 150 for what I consider as true friends. There wouldn't be enough time to devote to each one properly!

The history and research is fascinating. As there seems to be a difference in definition, then some consensus is needed before a true pattern of research can justify how many friends we really need.

Food for thought indeed. Well done with all that research!