Dunbar's Number, named for anthropologist Robin Dunbar, holds that humans can maintain roughly 150 stable social relationships at once. Inside that ceiling sit smaller circles: about 5 intimate bonds, 15 close ties, and 50 good friends. The limit is cognitive, not moral. Your brain only has so much capacity to track who people are, what they care about, and where you stand with them.
It works because attention is a finite resource that does not scale with ambition. As a founder, your contact list grows faster than your ability to actually nurture it. You end up with 200 "close contacts" and a low-grade guilt about every name you neglect. The model reframes that guilt as math: you are not failing at connection, you are exceeding a hard limit.
The practical move is deliberate triage. Pick the 15 relationships that genuinely matter to your business and life, and give them real, consistent attention. Let the remaining contacts be occasional and low-maintenance without apology. Depth in the right circle beats shallow upkeep across a list you can never truly hold.
Common mistake
Treating 150 as a target to fill rather than a ceiling to respect, so people keep adding contacts and spreading attention thinner instead of consciously choosing the 15 relationships that deserve real depth.
How to use it
Three ways to put it to work.
Everyday life
Your phone has 600 contacts and you feel guilty
You keep meaning to text people back and feel like a bad friend. Dunbar's Number says the guilt is misplaced: you cannot hold 600 stable ties, only about 150, with just 15 truly close. Scroll your contacts and name your real 15 - the people whose bad week you'd want to know about. Set a monthly reminder to actually reach those 15, and let the rest be people you're glad to see when paths cross.
Tech
Your startup hits 160 employees and culture frays
People used to know everyone; now Slack feels like strangers and decisions stall. That's the 150 ceiling - past it, one informal network can't stay stable and fractures on its own. Stop fighting it with all-hands; instead carve the org into squads of roughly 15 with their own rituals and a clear owner. Ship the reorg into ~10-person pods this quarter so trust and context live where the work happens.
Small business
Your agency juggles ninety active clients badly
You're answering everyone slowly and dropping balls, feeling like you fail at service. Dunbar's layers explain it: you can give real attention to about 15, not 90. Rank all 90 clients and pull the top 15 into a white-glove tier with a named contact. Move the remaining 75 to a self-serve portal with templates and a shared inbox, so your week stops being eaten by relationships you were never built to hold.
Reckon · Thinking tool
Dunbar's Number
Robin Dunbar, anthropologist (1992)
What it is
Humans can maintain roughly 150 stable social relationships. Inner circles are smaller: about 5 intimate, 15 close, 50 good friends.
When to use it
When you feel stretched thin across too many relationships and guilty about dropping any. You're not failing at connection. You're exceeding cognitive limits. Triage deliberately.
Work through it.
Print this (use the Save as PDF button up top) and fill it in on paper. Identify which relationships actually deserve your attention and deliberately let the rest be occasional.
01
THE FULL LIST: Write down every person you currently feel an obligation to maintain a relationship with: colleagues, clients, collaborators, investors, friends.
02
THE TIERS: Sort them into three groups: the 5 people who are closest and most critical, the 15 who are genuinely important, and the 50 who matter but less frequently.
Most people skip this step because it feels harsh. It is not. It is cognitive reality.
03
THE GUILT AUDIT: Who on your list are you maintaining out of obligation or inertia rather than genuine mutual value? Name them.
04
THE REALLOCATION: Write the specific attention you will give to your top 5 this month. Calls, meetings, messages - concrete and scheduled.
05
THE DECISION: For the guilt-audit names: move them to occasional contact, hand them off, or exit the relationship. Write one action per name.
Reckon · reckon.report · flip for the working template
Reckon · Working template
Dunbar's Number
Print double-sided. Read the how-to on the front; do the work here.
Write real names into each layer. The point is the limit: you cannot truly keep more.
5 · Corethe people you would call in a crisis
15 · Closethe friends you actually keep up with
50 · Friendspeople you would invite to something
150 · Networkstable ties: count them, you cannot list them all