How Many Professional Relationships Can You Actually Keep Up? Dunbar's Number, Its Layers and Its Critics

Most people on LinkedIn have far more connections than they could ever stay in touch with. Hundreds, often thousands. LinkedIn allows up to 30,000 1st-degree connections and unlimited followers^[8]. At some point the question comes up: how many of these people can I actually have a relationship with?

The usual answer is "150, Dunbar's number." That answer is half right, and the half that is wrong matters. Here is what the research says, what the critics say, and a system that works for a large professional network without pretending your brain can do more than it can.

Where 150 comes from

In the early 1990s, Robin Dunbar found that across primate species, the typical size of a social group tracked the relative size of the neocortex. Extrapolating that regression line to humans predicted a natural group of about 150^{[3, 4]}. The idea, called the social brain hypothesis, is that keeping track of relationships is cognitively costly, so there is a ceiling.

Dunbar and colleagues then looked for that number in real human networks:

• Christmas cards. In a 2003 study, 43 British households reported every card they sent, nearly 3,000 cards in all. Counting everyone in the households that received cards, the mean network size was 153.5. Counting only the people respondents said they actively contacted, it was 124.9^[1]. The spread was wide: the 153.5 average came with a standard deviation of 84.5.
• Facebook friends. A 2016 study of two UK samples (2,000 and 1,375 adults) found mean Facebook friend counts of 155.2 and 182.8. People in the first sample said only 27.6% of their Facebook friends were genuine friends, on average. The number of people they could rely on in a crisis averaged 4.1, and close friends averaged 13.6^[2].

That second study is the interesting one for LinkedIn users. Online tools made it easy to add people, but the inner circles stayed about the same size as offline^[2]. More connections did not mean more close relationships.

The layers: 5, 15, 50, 150 and beyond

The more practical part of Dunbar's work is the idea of layers. Relationships are not one flat list of 150. They come in rings, each roughly three times the size of the one inside it, with values that approximate 5, 15, 50 and 150, and wider rings at about 500 and 1,500^[2]. Dunbar describes the 500 ring as acquaintances, people you know well enough to have a conversation with, and the 1,500 ring as roughly the number of faces you can put names to^[2].

Two points from Dunbar's own summary are easy to miss. The layered structure is described as the result of "a trade-off between the time costs required to maintain different kinds of relationships and the benefits these provide." And there is "considerable variation between individuals due to gender, age, personality and social circumstances"^[3]. The numbers are averages. Some people's 50 is 25, and some people's is 80.

The criticism: maybe there is no number

In 2021, Patrik Lindenfors, Andreas Wartel and Johan Lind re-ran the brain-to-group-size analysis with newer primate data and modern statistical methods. Their estimates for average human group size were 69 to 109 with one method and 16 to 42 with another. The 95% confidence intervals were 4 to 520 and 2 to 336. Their conclusion: "specifying any one number is futile" and "a cognitive limit on human group size cannot be derived in this manner"^[4].

They also repeat a broader objection from earlier critics: humans have "cultural mechanisms, practices, and social structures" that work around cognitive limits, and other researchers have reported typical group sizes well away from 150^[4]. Think of a CRM, a calendar reminder or a notes app. We extend memory with tools all the time.

Dunbar's reply

Dunbar and Susanne Shultz responded that critical studies make a set of conceptual and statistical errors^[5]. In a 2024 commentary, Dunbar argues that critics fit one regression line through all primates when humans belong to a distinct "grade" with apes, which changes the prediction considerably. He also points to 23 studies of personal networks and communities that he says confirm a core group of about 150^[3].

What to take from the debate

This is an open scientific argument, and we are not going to settle it here. For your network, the exact number matters less than you might think. The disagreement is mostly about whether 150 can be predicted from primate brains. Nobody in it claims you can have deep relationships with thousands of people. The more direct evidence on what it takes to keep a relationship going comes from studies that measure time and contact, and that evidence is fairly consistent.

What actually limits you: time and contact

Two findings are more useful day to day than any headline number.

• Relationships cost hours. Communication researcher Jeffrey Hall estimated it takes roughly 50 hours together to go from acquaintance to casual friend, 90 hours to become a friend, and more than 200 hours to become a close friend. "Hours spent working together just don't count as much," the University of Kansas summary notes^[7]. That was friendship, not professional relationships, but the logic carries: closeness is built in time you choose to spend.
• Closeness fades without contact. Sam Roberts and Robin Dunbar followed 25 students' networks for 18 months as they left school. Emotional closeness to friends declined, even for friends they had known a long time. Declines were smaller where people kept up contact or did activities together^[6]. It is a small study, but it matches what most people notice after changing jobs.

Put those together and the conclusion is plain: you can't keep thousands of relationships close, and you shouldn't try. The good news is that you don't need to. Research on dormant ties found that people you have not spoken to in years can still give useful, fresh advice when you reconnect, and that these ties "require much less maintenance" while keeping a large network within reach^[9]. We cover that research in why reconnecting often beats new connections.

A practical system for a network of thousands

Use the layers as a rough guide to how much attention each group gets. The tier sizes below borrow Dunbar's numbers as rules of thumb, not cut-offs, and the contact rhythms are our suggestion, not something a study prescribes.

1. Inner circle (about 5 to 15). Mentors, cofounders, the people you would call in a crisis. You don't need a system for these. You need to show up.
2. Active circle (about 50). The people who matter most for what you are working on right now: investors if you are raising, buyers and champions if you are selling, a few peers. Real contact roughly monthly, a call or coffee where possible. Rebuild this list every quarter, because goals change.
3. Warm ring (about 150). People you like and respect and want to keep a thread with. A personal touch every few months: comment on their post, send a note when something happens, share something useful.
4. Wide ring (hundreds to a couple of thousand). Former colleagues, people from events and programs, past clients. Contact only when there is a moment: a job change, a work anniversary, a post you have a real view on. Nothing on a schedule.
5. Dormant pool (everyone else). No upkeep. When you have a real question or goal, search this pool for the right person and reconnect with a specific reason.

Do the time math

Say you give relationships 20 minutes on weekdays. That is about 85 hours a year. Fifty monthly touches of five minutes each is 600 touches, or 50 hours. That leaves around 35 hours for the warm ring, moments in the wide ring, and a few reconnections. It fits, but only because the outer rings are triggered by events rather than kept on a calendar.

Let the tiers move

Keep notes, because memory won't scale

Lindenfors and colleagues point out that humans use culture and tools to get past cognitive limits^[4]. Whatever the right number is, notes help: one line after each conversation about what they are working on and anything you promised. Next time, you start from context instead of a blank message. Our piece on relationship memory goes deeper on this.

Where a tool fits

The outer rings are where systems help most, because the work there is noticing: who changed jobs, whose anniversary it is, who in a few thousand people fits what you are doing this quarter. wait who? syncs your LinkedIn network, ranks people for the goal you set, and flags job changes and anniversaries so the wide ring gets a message when there is a reason. You can also ask about your network from Claude through the wait who? connector. The inner circle stays yours to keep up the old-fashioned way.

FAQ

Sources

1. Social Network Size in Humans (Hill and Dunbar). Human Nature 14(1), 2003. Author-hosted copy, Durham University.
2. Do online social media cut through the constraints that limit the size of offline social networks? (Dunbar). Royal Society Open Science, 2016. PubMed Central.
3. The social brain hypothesis: thirty years on (Dunbar). Annals of Human Biology 51(1), 2024. Open access copy, University of Oxford.
4. 'Dunbar's number' deconstructed (Lindenfors, Wartel and Lind). Biology Letters, 2021. PubMed Central.
5. Four errors and a fallacy: pitfalls for the unwary in comparative brain analyses (Dunbar and Shultz). Biological Reviews, 2023. University of Manchester Research Explorer.
6. Managing Relationship Decay: Network, Gender, and Contextual Effects (Roberts and Dunbar). Human Nature 26, 2015. Open access copy, Liverpool John Moores University.
7. How to make friends? Study reveals how many hours it takes (on Hall, Journal of Social and Personal Relationships). University of Kansas News, March 2018.
8. Network size limit. LinkedIn Help.
9. Dormant Ties: The Value of Reconnecting (Levin, Walter and Murnighan). Organization Science 22(4), 2011. Author-hosted copy, George Washington University.