If you’re putting together a project team, then you’re most likely considering ideal team size. Do you go with a large team, hence more brainpower potential, or a small team? At first sight, more people might seem to result in better or faster outcomes. But both research and experience show that small teams are in fact much more efficient than large teams.

Two-pizza Teams

Ideal Size Team Two Pizza Team
Werner Vogels, Amazon’s Vice President and CTO, tells us : “If a project team can eat more than two pizzas, it’s too large.” It’s good to keep this advice in mind as a rule of thumb. Vogels’s tactic is to assign tightly focused, small teams to solve one small problem at a time. The Agile software development method has a similar, though more
exact, approach: the recommended Agile team size is 7 +/- 2. That means the ideal team size is between 5 and 9.

Of course, the number of team members will vary with the function and goals of your team, as well as the activities it must perform. If you seek effective input, for example, the size of your team can go up to 18-20. But if you expect your team members to form a highly cohesive unit, keep it lower than 12.
One argument for this comes from U.K. anthropology professor R.I.M. Dunbar. In his paper on the relationship between humans’ neocortex size and group size, Dunbar writes that “... there is a cognitive limit to the number of individuals with whom any one person can maintain stable relationships” and “this limit is a direct function of relative neocortex size,” which in turn limits group size. That means that no matter what team strategies you can think of, our brains can only take so much interaction. Yes, humans can form a higher number of stable inter-personal relationships than, let’s say, chimpanzees, but if there are more than 10-12 team members the connections become too hard for us to maintain.


Along the grain of Prof. Dunbar’s research is the argument that smaller teams enjoy better communication. The study shows that about 60% of the time devoted to human conversations is spent on personal experiences and gossiping about relationships. It seems simple enough: the more people there are, the more time and effort goes into communication, the longer it takes to get things done. Not only are principles of cohesiveness and mutual accountability more difficult to achieve in larger teams, but your team’s productivity will also be affected by communication overhead.

Communication Pathways Communication Overhead
In his 1975 book The Mythical Man-Month, Fred Brooks put it nicely in an equation that calculates the number of communication pathways: [n*(n-1)]/2. If you have a team of 5, for example, you get [5 * (5-1)]/2 = 10 communication pathways, or channels. If the team has 10 members, then you have [10 * (10-1)]/2 = 45 channels. You get 5 extra team members for the price of 35 extra communication pathways - a sure recipe to slow down your project. Run this for larger teams, and you will see the communication pathways - and the time it takes to get the project done - dramatically increase.

Stay with odd numbers

It’s important that you avoid having an even number of members on your team to increase decisiveness. Having an odd number makes it impossible for the team to be equally divided on an issue. Consensus is reached quicker and productivity increases. Odd numbered teams also seem to achieve balance in group creativity and accountability without internal administrative problems.


It’s a fact that smaller teams stay more motivated. Larger teams tend to fall prey to the phenomenon of social loafing: the bigger the team size, the less individual effort. This phenomenon was discovered through a series of experiments by Max Ringelmann (so it's also called the Ringelmann effect) and it says that humans decrease their individual effort when working in teams.
There are several reasons for social loafing. Accountability decreases, as team members feel less individually responsible for the output. The overall effort and passion of the individual members also decrease, affecting the productivity of the whole team. Larger groups often make it easier for individuals to hide in the crowd and cruise by, thus affecting the whole team. If you really can’t influence the team size, then think about splitting tasks and building subgroups. Larger groups can work again once they reach around 20-25 members and can be divided in sub-teams of 5-9.

No doubt, a more focused small team working on single tasks is more efficient than a big team. Our advice is to ramp up your team’s productivity rather than its size.

What is the most efficient team size in your experience? Have you ever lead a large team? How did that work out? We’d love to hear from you in the comments below.