Dunbar’s Number
You can’t maintain meaningful relationships with 5,000 LinkedIn connections. Your brain literally can’t.
Dunbar’s Number (~150) (sometimes called the 150 rule) is the cognitive limit on stable social relationships: people you actually know, not just recognize. This number has held across tribes, military units, and companies. It’s biology, not preference.
Most importantly, Dunbar’s number isn’t just one number: it shows up as a hierarchy of layers (often summarized as 5/15/50/150).
What Counts as a Relationship?
When Dunbar says “stable social relationships,” he means people you can keep track of in context. Not just “someone whose name you know,” but someone where you can answer basic questions without checking a feed:
- What is happening in their life right now?
- What is your relationship history?
- How do they relate to other people in your network?
This is why social media inflates the feeling of connection without increasing the underlying capacity. You can see updates about thousands of people, but you can’t maintain thousands of relationships.
The Science Behind the Number
In 1992, British anthropologist Robin Dunbar was studying primate social groups. He noticed a pattern: the larger a primate’s neocortex (the “thinking” part of the brain), the larger their social group (Dunbar, 1992).
When Dunbar plotted neocortex size against group size for various primates, he found a consistent ratio. Extrapolating to humans, he predicted our natural group size: approximately 150 people.
He then tested this against real human data:
- Hunter-gatherer societies: Average clan size ~150
- Neolithic farming villages: ~150 people
- Roman army units (maniples): ~130 soldiers
- Modern military companies: ~150 soldiers
- Hutterite communities: Split when they exceed ~150
The number kept appearing. It wasn’t cultural preference. It was cognitive architecture.
Why 150? Maintaining a relationship requires remembering: who the person is, your history together, their relationship to others in your network, their current situation. This social bookkeeping consumes mental bandwidth. At ~150 people, we hit capacity.
The Layers
Relationships aren’t binary. They exist in concentric circles with hard capacity limits:
| Layer | Size | Description | Contact Frequency |
|---|---|---|---|
| Intimate | ~5 | Your closest people. Would call at 3am in crisis. | Daily/Weekly |
| Close Friends | ~15 | Strong emotional connection. Confide in regularly. | Weekly/Monthly |
| Friends | ~50 | Would invite to a group dinner. Know well. | Monthly |
| Acquaintances | ~150 | ”Meaningful” relationships. Would recognize at a party. | Occasionally |
| Recognizable | ~500 | Would recognize face/name. No real relationship. | Rarely |
| Known Faces | ~1,500 | Can attach a name to a face. That’s it. | Never |
Each layer is ~3× the previous (5 → 15 → 50 → 150 → 500 → 1,500). This reflects the cognitive cost of each intimacy level.
Why This Matters
Quality beats quantity. Life satisfaction correlates with your inner circles (5-15), not your follower count. 2,000 LinkedIn connections ≠ 2,000 friends.
Relationship investment is zero-sum. Every hour on weak ties is an hour not spent deepening strong ones. Are you investing in the right layer?
The modern paradox. More connections than ever. More loneliness than ever. We’ve expanded outer circles while starving inner ones. 500 Instagram followers doesn’t replace 5 close friends.
The Inner 5
Your life-or-death relationships:
- Would help you move a body (metaphorically)
- Know your real struggles, not your highlight reel
- You’d drop everything for them, and they for you
Requires hours per week and mutual vulnerability. Often: partner, best friends, close family.
The problem: Most people’s inner circle has atrophied. Lots of acquaintances, no one to call in crisis.
The Close 15
Your go-to people:
- You’d attend their wedding, visit them in hospital
- Real conversations, not surface chatter
- Know each other’s lives in detail
Requires weekly to monthly contact. The “dinner party” group.
The problem: Gets crowded out by obligatory relationships that don’t actually support you.
The Outer Layers (50-150)
Friends (50): Would invite to a party. Real conversations when you meet. Need periodic maintenance.
Acquaintances (150): Dunbar’s original number. You know who they are and how they relate to others. The natural size of tribes, military units, and functional companies.
What To Do
Audit your circles:
- Who would you call at 3am? → Inner 5
- Who do you share real struggles with? → Inner 5
- Who would you host for a weekend? → Close 15
- Who do you genuinely enjoy? → Friends 50
If your inner circles are sparse, that’s where to focus. Not LinkedIn.
Invest intentionally:
- Identify your target 5
- Invest disproportionately: hours, not minutes
- Prune draining obligatory relationships
- Accept the limit. You can’t be close with everyone.
Social media: Useful for the 150-500 layer. Harmful if it substitutes for 5-15. Likes aren’t relationships.
Failure Modes
Common ways people end up socially “busy” but still lonely:
- Over-investing in the 150 layer: You show up to events, keep up with group chats, and still have nobody you can call in a crisis.
- Life transition wiped your inner circles: Moving, kids, divorce, career changes. If you don’t rebuild intentionally, your inner 5 becomes zero.
- Confusing familiarity with intimacy: Coworkers, old classmates, and online communities feel like connection, but the relationship doesn’t survive real stress.
- All maintenance, no creation: You preserve existing ties but don’t add new ones, so the network shrinks as life changes.
If you recognize yourself here, prioritize rebuilding the inner layers first: 5 and 15.
Why Organizations Break at 150
- Small companies feel different: everyone knows everyone
- Military companies are ~150 soldiers
- Villages stabilized around 150 people
- Startups lose culture when they cross 150 employees
Beyond 150, informal relationships can’t hold the group together. You need hierarchy, formal processes, and org charts. The “family feel” disappears because your brain can no longer track everyone.
Does Social Media Change This?
No. Research consistently shows that digital connections don’t expand our cognitive limits (Dunbar, 2016).
What social media does:
- Makes maintaining weak ties (150-500) easier
- Helps you stay loosely connected to acquaintances
- Provides an illusion of connection without the depth
What social media doesn’t do:
- Increase the number of close relationships you can maintain
- Replace the need for face-to-face time with inner circles
- Substitute for the hours required to build intimacy
You can have 5,000 followers and still only 5 close friends. The followers are in your “recognized faces” layer, not your friendship layers. Different cognitive systems entirely.
The Debate
Some researchers argue the exact number varies (100-250 depending on individual and culture). Others question whether the neocortex-to-group-size correlation holds as cleanly as Dunbar claimed.
What’s not disputed: There IS a limit. You cannot maintain meaningful relationships with unlimited people. The capacity is measured in dozens to low hundreds, not thousands. The exact number matters less than the principle: your attention is finite, and relationships require attention.
Exercise: Map Your Circles
Take 30 minutes and do this quickly without overthinking.
Step 1 (5 minutes): Inner 5 (Would call at 3am)
Step 2 (10 minutes): Close 15 (Would host for a weekend)
Step 3 (10 minutes): Friends 50 (Would invite to a party)
You don’t need all 50 written out. If you can’t name at least 10 without effort, your friendship layer is likely thinner than you think.
Step 4 (5 minutes): Choose one move
- If Inner 5 is sparse: schedule one 1:1 this week.
- If Close 15 is sparse: host something small this month.
- If Friends 50 is sparse: join a recurring community and attend weekly for 8 weeks.
Maintenance cadence (rule of thumb):
| Layer | Keep it alive with |
|---|---|
| Inner 5 | Weekly touchpoint |
| Close 15 | 1-2 meaningful interactions per month |
| Friends 50 | Quarterly hangout or check-in |
| 150 layer | Occasional updates and opportunistic connection |
If your inner 5 has gaps, that’s where to focus. Not on growing your LinkedIn network.
Related
- The Loneliness Epidemic: What happens when inner circles are empty
- Weak vs Strong Ties: Different relationship types serve different purposes
- Friendship Maintenance: The protocol for preventing decay
- Building New Friendships: How to fill sparse circles
- The Giver’s Paradox: Why generosity builds connection
You cannot have 1,000 friends. You can have 5 close friends and 145 acquaintances.
5,000 LinkedIn connections and no one to call in crisis = wrong metric. Depth beats breadth.