The question of what constitutes the ideal team size for software development remains as relevant as ever. While there is no one-size-fits-all answer, most experts agree that the most effective teams consist of 5 to 9 people. This is supported by research and the practical experience of successful projects. Let’s explore why this range is considered optimal and what impacts a team’s efficiency.

Why Are Smaller Teams More Effective?

As the number of team members grows, so do the challenges of management and communication. Each additional person increases the number of connections within the team, which means more time is required for discussions, task alignment, and decision-making.

For example, a team of 5 people has only 10 potential connections, where everyone communicates with everyone. But a team of 10 has 45 connections, and a team of 15 has 105. Managing these connections becomes exponentially harder.

In larger teams, discussions often drag on, turning into debates, and actions become fragmented. Problems pile up: tasks get lost in an overload of unnecessary messages, decisions take too long, and overall efficiency plummets.

Activity in Larger Teams: 3–5 Members Do Most of the Work

No matter how large the team, only 3–5 members are typically the most proactive and take the lead in getting things done. Others tend to adopt a more passive role, waiting for direction or following the lead of those who are more engaged.

This phenomenon is linked to the concept of social loafing, identified in psychological studies. The larger the group, the less responsibility each individual feels for the overall result.

Efficiency and Ivan Steiner’s Law

Team efficiency is directly related to its size. Research by Ivan Steiner found that:

1. Increasing the number of team members reduces productivity due to the complexity of communication.

2. Each new member requires the reallocation of attention and resources to integrate them into the workflow.

3. The productivity gains of adding new members diminish with each addition.

In simple terms, team efficiency drops exponentially as the team size increases. This highlights why smaller groups tend to achieve better results — they are more cohesive and can communicate faster.

What Do the Experts Say?

1. Scrum, one of the most popular software development methodologies, recommends team sizes of 3 to 9 members. This range balances the availability of necessary skills with manageable communication.

2. Elon Musk mentioned in an interview that 5 people is the ideal team size for solving complex problems. He emphasized that this minimizes unnecessary discussions and accelerates decision-making.

3. Jennifer Mueller, a professor of organizational behavior, also highlights that teams of 5 members are the most effective for projects requiring speed, creativity, and clarity.

Brooks’ Law: More People, More Problems

Brooks’ Law, introduced by Fred Brooks in his book “The Mythical Man-Month”, states:

“Adding more people to a late project only makes it later.”

Why? Because every new member requires:

• Time for onboarding and getting up to speed.

• Redistribution of tasks among existing team members.

• Increased communication overhead to ensure alignment.

As a result, the team’s productivity doesn’t improve — in fact, it often declines.

The Problem of Scaling Communication

The main challenge of large teams lies in communication. It doesn’t scale horizontally, and as the number of team members grows, managing the flow of information becomes exponentially harder.

For example, in a team of 5 people, it might take just an hour to align on tasks. But in a team of 15, you’d need three times as long just to ensure everyone is on the same page.

Additionally, excessive communication distracts team members from their actual work. Instead of solving specific problems, they get bogged down in organizational discussions.

Recommendations for Effective Teams

1. Keep teams compact. If fewer people can accomplish the task, go with a smaller team. It’s faster, less stressful, and more efficient.

2. Clearly define roles. Each team member should have a clear understanding of their responsibilities to minimize conflicts and duplication of effort.

3. Leverage technology for communication. Modern project management tools can automate routine tasks and improve transparency.

4. Avoid adding people at the last minute. If a project is behind schedule, adding more members will likely make things worse, not better.

The Sweet Spot: 5 to 9 Members

While the ideal team size depends on the project and context, research and experience consistently show that a team of 5 to 9 members is the most efficient. This size minimizes communication friction, keeps members proactive, and ensures faster results.

Remember, adding more people doesn’t always lead to better outcomes. Sometimes, small, well-coordinated teams can achieve incredible things.