𝗪𝗵𝘆 𝗱𝗼𝗲𝘀 𝗩𝗮𝗹𝘃𝗲 𝗵𝗮𝘃𝗲 𝗻𝗼 𝗺𝗮𝗻𝗮𝗴𝗲𝗿𝘀

Valve Corporation has no managers, no hierarchy, and no org chart. Engineers pick their own projects. Teams form themselves and cap at 12. When a project needs more than 15, they split it. At 50, they divide it. At 150, they open a new office.

This is Dunbar's Number applied as company policy.

Robin Dunbar published the idea in 1992. While studying primates, he found a correlation between brain size and the size of the social group each species could maintain. For humans, the number came out to about 150. The upper limit on stable social relationships.

But 150 isn't the whole story. Dunbar identified four layers:

- 𝟱 are intimate relationships

- 𝟭𝟱 are trusted collaborators

- 𝟱𝟬 are close working relationships

- 𝟭𝟱𝟬 are stable social connections

Each layer matters in engineering. High-trust work happens in groups of 5. Teams that need real collaboration lose cohesion past 15. A division of 50 still feels like a community, but a department of 150 is roughly the upper bound where you can recognize everyone.

Above 150, you don't have a community. You have a company.

Most engineering orgs hit this and often don't acknowledge it. They keep the all-hands. They run engagement surveys asking why people feel disconnected. They ship culture decks. None of it works. The issue isn't motivation. The human brain can't keep tabs on 800 colleagues.

The orgs that handle scale well stop fighting the limit and design around it.

Amazon's two-pizza teams (5-10 people) sit inside the smallest Dunbar layer. The Linux kernel handles thousands of contributors through subsystem mailing lists. Each maintainer talks to a small group of direct peers, not the whole community. Same law, different shapes.

The lesson for engineering leaders is uncomfortable. Past a certain size, adding people doesn't add capacity. It only adds coordination cost.

If your team is over 15, working trust has probably started to fray. If your division is over 50, the all-hands isn't bringing people together.

If your organization is over 150, the org chart isn't describing how work happens. The people in subgroups are.