Home / Glossary / Dunbar's number and your professional network
Dunbar's number and your professional network
Definition: Dunbar's number is the idea that most people can maintain about 150 stable, meaningful relationships at one time. Anthropologist Robin Dunbar proposed it in 1992 after linking brain size to social group size in primates. For professionals, it is a useful rule of thumb, not a hard limit: your attention is finite, so the relationships you keep warm need deliberate choices.
Dunbar's number comes from Dunbar, R. I. M. (1992), "Neocortex size as a constraint on group size in primates," Journal of Human Evolution, 22(6), which proposed that humans can maintain about 150 stable relationships.
On this page
Why it matters
If your work runs on relationships, you will always know more people than you can actively keep up with. Dunbar's number gives that tension a name. It explains why contacts drift even when you like them, and why trying to stay close to everyone usually means staying close to no one.
It also shifts the question from "How big is my network?" to "Who am I actually keeping warm?" That is a better question. It pushes you to choose your core relationships on purpose, then set up a lighter, steady way to stay in touch with everyone else.
How it works
Where the number comes from
Robin Dunbar compared primate species and found that the size of the neocortex tracked the size of their typical social groups. He extended that pattern to humans and estimated that people can hold roughly 150 stable relationships: people you know personally, know how they connect to others, and would greet warmly if you ran into them. The idea is that relationships cost mental effort and time. You have to remember context, follow what is happening in someone's life, and show up now and then. That cost puts a natural ceiling on how many real relationships one person can carry.
Has it been debunked?
Not fully, but the exact figure is contested. Critics point out that the estimate comes from extrapolating a primate pattern to humans, which leaves a wide range of uncertainty. Some argue that culture, personality, job and tools shape how many relationships a person can manage, so a single fixed number is too neat. A fair reading: the precise count of 150 is debatable, while the core idea holds up in everyday experience. Your capacity for close, active relationships is limited, and it is far smaller than your contact list.
Beyond the 150: weak and dormant ties
Dunbar's number describes relationships you actively maintain. It does not mean people outside that group are useless. Granovetter (1973) showed that weaker acquaintances often bring new information your close circle cannot. Levin, Walter and Murnighan (2011) found that executives who reconnected with dormant contacts got advice that compared favorably with advice from their current contacts. So the practical model is layers: a small core you invest in often, a wider ring you touch lightly, and a large pool of dormant ties you can revive when there is a real reason.
Examples
- A financial advisor has 600 clients and prospects in her files but realizes she only has real, two way relationships with about 120 of them. She picks those as her priority group and moves the rest to a quarterly check in.
- A recruiter with thousands of LinkedIn connections stops treating that number as his network. He tracks a short list of hiring managers and candidates he actually talks with and reviews it monthly.
- A founder notices that after a busy fundraising year, several early mentors have quietly fallen out of his active circle. He sends each a short update with a specific thank you, restoring the relationships without pretending nothing changed.
- A nonprofit major gifts officer accepts that she cannot personally steward every donor. She keeps a focused portfolio for deep relationships and uses lighter, regular touchpoints for the wider donor base.
Putting it into practice
- List the people you would genuinely be glad to hear from and who would be glad to hear from you. This is your working core, whatever its size.
- Split your contacts into layers: a small inner group you contact often, a middle ring you reach a few times a year, and a dormant pool you revisit when you have a reason.
- Set a simple cadence for each layer and put it on your calendar so staying in touch does not depend on memory.
- Keep brief notes after each conversation (family news, projects, what they asked for) so your next message picks up where you left off.
- Once a quarter, look for dormant ties worth reviving. Reach out with a specific reason, such as a shared interest, a question or a useful introduction.
- Let some relationships move to a lighter layer without guilt. Rotating who gets your attention is normal and keeps your effort honest.
Write the message in 20 seconds
Free, no signup. The example is filled in: press the button, then replace it with your own situation. In Capstone, a message like it is written for each person you know when their check-in is due.
Frequently asked questions
What is Dunbar's Number?
Dunbar's number is the estimate that a person can maintain about 150 stable, meaningful relationships at once. Robin Dunbar proposed it in 1992 based on the link between neocortex size and group size in primates. It refers to people you know personally and keep in some real contact with, not everyone you have met or connected with online.
Is Dunbar's number real?
Yes, as a general principle, though the exact figure is debated. The core idea, that limited time and attention cap how many close relationships you can keep, matches most people's experience. Critics argue the specific number of 150 is too precise and varies by person and context. Treat it as a useful rule of thumb rather than a fixed law.
Has Dunbar's number been debunked?
No, it has been challenged rather than disproven. Critics question extrapolating a primate pattern to humans and say the true range is wide and varies with culture, personality and job. Those points weaken the idea of one exact number. They do not overturn the basic insight that your capacity for active, meaningful relationships is limited.
Does Dunbar's number apply to LinkedIn connections?
Not directly. Dunbar's number describes relationships you actively maintain, not the size of a contact list. You can have thousands of connections while only keeping up with a small group. Those wider connections still matter, since weaker ties often carry new information and opportunities, but they need a lighter, different kind of attention than your core relationships.
How should I use Dunbar's number in my professional network?
Use it to prioritize, not to cap your network. Identify the relationships you want to keep truly warm, give them regular attention, and set a lighter rhythm for everyone else. Revisit dormant contacts when you have a genuine reason to reach out. The goal is to spend your limited attention deliberately instead of letting relationships fade by accident.
Can you really keep up with 150 people? Put them all on a rhythm in Capstone, from a few weeks to three months apart. When someone is due, a check-in is written for you. If you talked lately, it waits.
Start 14 days free, then $25/mo
A study of 20 million LinkedIn members found that acquaintances, more than close friends, led to new jobs (Science, 2022). Capstone keeps those people warm. You approve every message, and it goes from your own email or phone.