There is no formal definition of how many participants there should be in a Mastermind group. In fact any group of 2 or more people working together can be considered a Mastermind Group.
So how do you find the ideal size?
Let’s skip the theoretical definition for the moment and focus on the results we want to achieve. A Mastermind Group should be a group of people who work together to help each other achieve their personal or professional goals.
Theoretically, the more people in the group the better, because the more people there are, the more experience is provided and the more ideas can be achieved.
But on the other hand, we must not lose sight of the fact that we work with people and there is an important psychological component to how they behave. When a group is too big it becomes a crowd and the commitment of each of the participants is blurred.
You should ask yourself three questions before deciding how many members there should be in your Mastermind group:
How much total time is available at each meeting?
Meetings should start and end on time, and those longer than 90 minutes can be exhausting. Over time the energy level will decrease significantly.
Also, as meetings get longer there may be people who can’t spend as much time on it, so they may exclude themselves from a group that does very long sessions.
A basic principle is that all participants should be able to participate in all sessions, ideally with similar time for all participants. Occasionally, a session can focus on a specific problem of one of the participants, but it should be avoided that a participant has to go through several sessions without being able to be heard and mentored.
Bearing all this in mind, the first thing to be decided is how long each meeting will last.
How long should each member be in each session to talk about their problem, challenge or decision?
Members need time to first verbalize their situation before planning can begin in earnest. Some members are quick and can summarize it in five minutes or less. Others need 10-15 minutes just to set the scene. It will also take additional time to brainstorm after the presentation of the topic.
The usual time for each participant should normally be between a minimum of 15 and a maximum of 30 minutes. Depending on the group dynamics, it could be set at more or less within that range.
What other topics are on your agenda?
Remember that every meeting usually includes some kind of opening and closing. There may be a review of the results of what was achieved during the week, commitments for the next one, introduction of new members as well as possible guest speakers, training or other events. Leave time for those on your working group agenda, and then plan accordingly.
So what is the ideal group size?
The ideal size of a Mastermind group is usually between 4 and 6 participants. Less than 4 is feasible but the contribution to supporting each of them can be quite low (there are only 2 people contributing new ideas). More than 6 means that the session must be extended while little time is spent on deepening the problems or challenges of each participant, which can be perceived as a waste of time for the participants.
Is it possible to make larger groups?
Of course, but then the dynamic changes. You will probably need half-day sessions or more. They should include breaks, perhaps even lunch. In the professional environment this probably means that the frequency of meetings should be lowered. It’s possible to have half-day meetings with 10 or 12 people that include lunch, but then they usually turn into once-a-month meetings. It is, however, perfectly valid and possibly very useful for high level professionals whose availability is more limited.