Why large teams slow down: the tipping point where size starts to hurt
In a recent post, I wrote about organisations needing to behave less like rigid hierarchies and more like adaptive systems, where coordination is designed rather than assumed. But coordination is not free; the more people involved, the harder it becomes. At some point, the effort required to stay aligned can slow everything down.
In 1975, computer scientist Fred Brooks published The Mythical Man-Month, drawing on his experience managing large software programmes at IBM. One idea from the book became famous:
“Adding manpower to a late software project makes it later.”
This might sound counterintuitive. If work is behind schedule, surely adding more people should help. But Brooks highlighted something many leaders still underestimate: people do not arrive as pure productive capacity, they also bring co-ordination cost. New joiners need onboarding, existing team members must explain context, work must be repartitioned, decisions need more voices, dependencies increase, communication overhead grows.
Sometimes the additional capacity helps, often the extra complexity arrives faster than the extra output.
Then came Dunbar
Years later, anthropologist Robin Dunbar studied the relationship between primate brain size and social group size, later extending the work to humans.
This led to the widely discussed idea of Dunbar’s number: that humans have cognitive limits on the number of stable social relationships they can comfortably maintain. The exact number is debated and often oversimplified, but the core insight remains valuable; human social capacity is finite. We can only sustain so many meaningful working relationships based on trust, shared context and regular interaction.
This matters enormously inside teams.
What Brooks and Dunbar suggest together
Brooks’ point about coordination overhead and Dunbar’s ideas around relational limits point to the same practical truth: as teams grow, performance does not rise in a straight line. At some point, size starts introducing drag.
Communication paths explode because more people means more potential interactions, updates and misunderstandings. Trust becomes harder because you cannot build strong working relationships equally with everyone. Alignment weakens because shared understanding fragments into pockets. Meetings can multiply because conversation becomes the mechanism for keeping everyone connected, and ownership blurs because the larger the group, the easier it is to assume someone else has it covered.
The hidden maths of growth
A team of 5 people has 10 possible one-to-one communication channels. A team of 10 has 45. A team of 15 has 105. You do not experience this as mathematics.
You experience it as:
more Slack messages
more status meetings
more duplicated conversations
slower decisions
more rework
less clarity
Why large teams often create false efficiency
Leaders sometimes prefer bigger teams because they look efficient on paper. One manager, one department, one roadmap, one budget. But visible simplicity at the org chart level can hide complexity at the interaction level.
A 14-person team may appear cheaper to manage than two 7-person teams, but those two smaller teams may move faster, own outcomes more clearly, and require less internal coordination. This is where many organisations optimise for management convenience rather than flow.
This does not mean tiny teams solve everything
Small teams may duplicate work, drift apart, lack necessary skills, create handoff problems of their own. So the lesson is not: “Always make teams smaller.”
The lesson is: there is usually an effective size range where a team can coordinate easily, build trust, and own meaningful outcomes without drowning in overhead. Beyond that point, growth can reduce performance.
What to look for in your own teams
You can often tell when a team has grown beyond its effective size without looking at the org chart. Look for signs like:
decisions that require “just one more conversation”
work that has to wait for people to align
repeated explanations of the same context
ownership that feels shared, but the reality is that no-one owns it
Team size is not just a resourcing decision, it is a coordination design decision. Every additional person increases potential capacity, but it also increases the number of relationships that must stay aligned. At some point, the cost of keeping everyone aligned outweighs the benefit of adding more hands and that’s the tipping point where teams start to feel busy, but slow.
A practical shift
When delivery slows, many organisations ask:
“How do we add more capacity?”
A more useful question is:
"How do we reduce the coordination burden required to make progress?"
Sometimes that means adding people.
Often it means:
narrowing the scope that a team owns
splitting teams into smaller, focused units
clarifying ownership boundaries
reducing the number of people needed to make decisions
Final thought
Most organisations don’t set out to create slow, hard-to-coordinate teams; they get there gradually. A team grows to handle more work, another person is added to reduce pressure, more perspectives are included to improve decisions.
Each step makes sense on its own, but over time progress starts to depend on more people staying aligned. That’s the tipping point; the moment where the way the work is organised begins to work against itself.
Once you see it, the problem looks different; it’s no longer about how to get more people involved, it’s about how to design things so fewer people need to be.
Are you sensing that some of your teams are reaching, or have reached, a tipping point where coordination is costing more than it should? If the answer is yes and you are unsure where to start untangling the mess, feel free to get in touch.
