At first glance, it may appear that more is better when it comes to deciding on the size of your board of directors.  Each additional board member brings new contacts and perspective to the table.  A bigger rolodex and more ideas - why not?

Well it turns out there is a cost to scaling your board.  More is not always better.

There are two problems that become more significant as boards get larger.  First, scheduling can become a real problem.  Institutional investors are often juggling portfolio companies, new investments and relationships with limited partners, making it a challenge to schedule future board meetings. 

This can create more than an administrative problem.  With too large of a board you may find that you can't get everyone in the room at the same time, leaving at least one person to lose the benefit of having continuity between meetings.  The CEO will always be working to catch somebody up on what was discussed last time.

The second issue with large boards is that they are usually less effective in providing guidance.  Have you ever tried to have a discussion in a group of 20 people?  It generally doesn't work.  You're more likely to have a productive debate about key company issues with a relatively small group.  Constructive dialogue dies out once a board reaches a certain size, leaving board meetings to be a one directional update (management updating the board) rather than a highly engaged conversation. 

Given these constraints early-stage companies usually have boards that range in size from 5-10 members.  The sweet spot appears to lie at the lower end of the range:  5-7 members. 

When you're negotiating the structure of your board with an investor keep these targets in mind.