Communication Channels Game: Keep a Growing Team in Sync
What is the communication channels formula?
The communication channels formula counts how many one-to-one conversations exist on a team: channels = n × (n − 1) ÷ 2, where n is the number of people. Every pair of people is one channel. Because every new person opens a channel to everyone already there, channels grow quadratically while the team grows one person at a time.
Team size vs. channels
| People (n) | Channels: n(n − 1) ÷ 2 | Feels like |
|---|---|---|
| 3 | 3 | A coffee chat. Everyone hears everything. |
| 5 | 10 | A tight squad. Still self-synchronizing. |
| 8 | 28 | Updates start getting missed without structure. |
| 10 | 45 | The Scrum guideline's upper edge for one team. |
| 15 | 105 | Nobody knows everything. Structure is mandatory. |
| 20 | 190 | This is a program, not a team. |
A worked example
A classic PMP exam question: your team grows from 8 people to 10 people. How many new communication channels were added?
At 8 people: 8 × 7 ÷ 2 = 28 channels. At 10 people: 10 × 9 ÷ 2 = 45 channels. The answer is 45 − 28 = 17 new channels. Headcount grew 25%, but coordination load grew 61%. That mismatch, not anyone's incompetence, is why the game gets away from you: it is also why real teams past about 10 people split up or add deliberate communication structure.
Watch: communication channels in 90 seconds
Read the transcript
You and two friends are starting a podcast. Managing the team is easy, right? Just one group chat. Everyone knows what everyone else is doing.
But then your channel blows up. You hire an editor, a thumbnail designer, a social media manager. Suddenly you have six people on the team.
You might think: okay, double the team, double the communication. Wrong. It doesn't double. It explodes.
In project management there's a formula for this. N times N minus one, divided by two. N is the number of people. With three people there are three communication channels. With six people, 15 channels. With 10 people, 45 channels.
The team grows linearly, but the communication pathways grow quadratically. That's a fancy way of saying it gets messy fast.
This is why big projects fail. People assume communication just happens. But as the team grows, communication isn't just a side task. It is the job.
Ready to test your skills? Try the Telephone Tree game and see if you can keep the team in sync.
Frequently asked questions
How do you calculate communication channels?
Communication channels = n × (n − 1) ÷ 2, where n is the number of people. Every person can talk to every other person, and each pair counts once. A team of 5 has 10 channels; a team of 10 has 45; a team of 15 has 105.
Why does adding one person add so many channels?
A new teammate opens a channel to every existing member, so the Nth person adds N − 1 new channels. Going from 8 people (28 channels) to 10 people (45 channels) adds 17 channels: the team grew 25% but its coordination load grew 61%. That gap is why growing teams feel disproportionately harder to keep in sync.
Is the communication channels formula on the PMP exam?
Yes. It appears in communications management questions, usually as "a team grows from X to Y people; how many new channels were added?" Compute both totals with n(n-1)/2 and subtract. Remember to include the project manager and any named stakeholders in n if the question does.
How does team size affect communication?
Coordination overhead grows quadratically while headcount grows linearly, which is the insight behind small-team practices: Scrum recommends teams of 10 or fewer, and Amazon popularized the two-pizza team. Past roughly 9 or 10 people, most organizations split into sub-teams and add deliberate communication structure instead of relying on everyone talking to everyone.
Want more practice? Try On the Spot, our earned value management game, or try Risk Expedition, our risk-response game, or browse all practice games.
You're the PM in the middle. Every line between two teammates is a communication channel, and channels go stale fast.