The “Magic Number” That Breaks Teams: Why 100-150 People Changes Everything

Once you cross 100 staff in your team, the physics of your business changes. Suddenly, everything feels heavier, slower, and unnecessarily political.

You’re not imagining it. You’ve hit a real inflection point.

There’s a reason leaders across industries experience friction at roughly the same scale; Dunbar’s number. Evolutionary psychologist Robin Dunbar suggests that around 150 is the cognitive limit for maintaining stable social relationships.

But 150 is for groups that have a very high incentive to remain together, meaning you will hit it earlier if your people have less than very high incentives.

And in business, we feel it immediately.

Up to ~80 people, teams operate on proximity:

• Leaders know everyone

• Decisions travel informally

• Culture is “felt,” not written

• Managers succeed through effort and goodwill

But, between 100-150 people, that model breaks.

Why things start to wobble

1. Span of control expands massively

Senior leaders suddenly have too many direct and indirect reports. Decision rights blur. Everyone seems busy, but accountability weakens. People stop knowing who decides, only who to chase.

2. Managers are promoted faster than they’re developed

Strong individual contributors become managers- but without tools, expectations, or training. Feedback becomes inconsistent. Standards drift. High performers feel it first, and start quietly reassessing their future with you.

This is where retention risk begins, even before results drop.

3. Communication complexity spikes

• A team of 10 has 45 communication lines.

• A team of 150 has 11,175.

Without structure, meetings multiply. Context gets lost. Misalignment gets labelled as “motivation” or “engagement” problems.

4. Culture stops scaling by default

What used to be “obvious” about your culture is interpreted differently by different leaders. Sub-teams form their "own" ways. Fractures form, because the (lack of) systems allow it.

5. Leaders confuse effort with control

Your instinctive response is to lean in harder: more meetings, more approvals, more control. Be the hero your team needs.

It feels responsible, but it slows everything down.

How do we get through it?

You don’t need to be the hero anymore. You need to design a management system.

1. Create explicit decision rights

2. Set clear management standards (based on your values, not unique personalities)

3. Over-communicate the why; give managers less priorities, that must be executed consistently

4. Define the operating cadence, stop relying on ad-hoc updates

5. Get managers trained on everything leadership before problems show up

If you don’t intentionally redesign how your organisation runs well before 150 people, it will redesign itself, and not in your favor.

Rest assured- A breakdown at this size isn’t failure. It’s a sign of growth.

Whether you are a Regional Director or CEO of a growing business, you cannot culture your way out of this with more pizza parties.

Stop “running a big team”, and start leading a business.