The challenge of meeting attendance is a delicate balancing act. When you invite too many people, you risk creating chaos where nothing gets accomplished. When you invite too few, you might miss critical decision makers or information providers. Getting this balance right requires understanding both the psychology of group dynamics and practical frameworks for determining optimal attendance, such as those outlined in the HBR Guide to Making Every Meeting Matter. By the end of this lesson, you'll have clear criteria for deciding not just who should attend your meetings, but how many people will make each meeting most effective.

Every manager has experienced the meeting that starts with good intentions but devolves into unfocused discussion because there are simply too many voices in the room. With too many attendees, it becomes nearly impossible to focus everyone’s time and attention on a single objective, and social dynamics make it hard for people to self-select out of irrelevant portions. The complexity of communication increases rapidly with each additional person, and large meetings often lead to a diffusion of responsibility, where individual effort drops—resulting in only a few people actively participating while others disengage.

On the other hand, having too few attendees creates different but equally damaging problems. Missing key decision makers or information providers means meetings end with unresolved questions or speculative discussions, and decisions can’t move forward. Excluding those who will be required to implement decisions leads to poor execution and lack of ownership, often resulting in more time spent on rework, clarification, and buy-in after the meeting than would have been spent including them in the first place.

The solution to attendance challenges isn't about setting arbitrary limits or sending open invitations—it's about systematically identifying the types of people who truly need to be present. There are five essential categories of participants to consider when deciding who should be included in your meeting. Think of these not as rigid rules, but as filters to help you make intentional decisions about who should be included in your meeting:

1. The key decision makers for the issues involved: These are the people with actual authority to commit resources, approve plans, or make binding choices. If any of these people need to "check with their boss" before agreeing to anything, they're not a decision maker.
2. Those with information and knowledge about the topics under discussion: These are your subject matter experts who understand the technical constraints, know the customer requirements, or have the historical context that informs good decisions. A common mistake is inviting everyone who knows something about the topic rather than identifying who has the specific knowledge needed for this particular discussion.
3. People who have a commitment to or a stake in the issue: These stakeholders will be significantly affected by the meeting's outcomes, even if they're not decision makers or implementers. Their buy-in often determines whether decisions succeed or fail. However, having a stake doesn't automatically mean they need to attend—sometimes their interests can be represented by others or their input gathered beforehand.
4. Those who need to know about the information in order to do their jobs: These people might not contribute to the discussion, but without understanding the decisions and context, they cannot perform their roles effectively. Here's where you need to be disciplined: do they need to be in the meeting to absorb this information, or would a thorough briefing afterward suffice?
5. Anyone who will be required to implement decisions made: These are the people who will actually do the work that flows from your meeting's decisions. Their presence ensures that implementation challenges surface during discussion rather than after commitments have been made. They can provide reality checks on timelines, identify resource needs, and flag potential obstacles that decision makers might not anticipate.

Once you know who should be considered for your meeting, you still need to determine how many people make sense for your specific purpose. It is recommended to use the 8-18-1800 rule:

• For decision-making or problem-solving, keep the group to 8 or fewer to ensure everyone can contribute and decisions can be made efficiently.
• For brainstorming, you can expand to as many as 18 to maximize diversity of ideas without losing control of the discussion.
• If the meeting is simply to provide updates, you can invite as many as needed (these are more like presentations than true meetings). However, if everyone is expected to give an update, keep it to 18 or fewer to avoid disengagement.
• For large-scale events meant to rally the team or share a vision, such as company all-hands or major announcements, the group can be as large as 1,800 or more.

The key is to match your attendee list to your meeting’s purpose: smaller for decisions, larger for sharing information or building energy.

The real value of the 8-18-1800 rule is that it forces you to clarify your meeting’s objective before finalizing the attendee list. Every additional person adds complexity and reduces engagement, while excluding the wrong people can lead to missed input or resentment. Use these guidelines to make intentional, purpose-driven choices about who to include.

Here’s how a manager might apply the 8-18-1800 rule when planning a meeting:

• Victoria: I’m finalizing the attendee list for next week’s budget meeting. I have twelve people, but I’m not sure if that’s too many.
• Ryan: What’s the main goal—making a decision?
• Victoria: Yes, we need to reallocate the budget.
• Ryan: Then aim for no more than eight people. Who are the key decision makers and essential contributors?
• Victoria: The CFO, the senior analyst, and the three department heads.
• Ryan: That’s five. The rest can be updated afterward.

By focusing on the meeting’s purpose and using the 8-18-1800 rule, Victoria reduces her list from twelve to five, ensuring a more effective decision-making session.

Mastering the art of choosing the right attendees is essential for running effective, focused meetings that drive results. Next, you’ll work through realistic scenarios to decide who should attend different types of meetings, navigate conversations with colleagues who aren’t invited, and develop strategies to keep non-attendees informed. These upcoming practice sessions will help you build confidence and skill in right-sizing your meetings for maximum effectiveness.