Rule of 7: The Ideal Work Group Size

Last Updated Sep 28, 2010 12:18 PM EDT

In the movie The Magnificent Seven, a group of crusty gunfighters led by Yul Brynner successfully protects a small Mexican village from desperadoes. The movie itself is a remake of Akira Kurosawa's Seven Samurai.

As it turns out, seven is a great number for not only forming an effective fictional fighting force, but also for task groups that use spreadsheets instead of swords to do their work.

That's according to the new book Decide & Deliver: 5 Steps to Breakthrough Performance in Your Organization (Harvard Business Press).

Once you've got 7 people in a group, each additional member reduces decision effectiveness by 10%, say the authors, Marcia W. Blenko, Michael C. Mankins, and Paul Rogers.

Unsurprisingly, a group of 17 or more rarely makes a decision other than when to take a lunch break.

Larger groups only seem to work when they adopt a strict set of governing policies, such as spelling out when a majority is needed to ratify a decision versus a plurality. But just getting agreement on those policies alone can be several meetings worth of work.

So my advice: If you have a choice when forming a group, limit membership to seven or less. And choose Yul Brynner as your team lead.

(Photo by Flickr user Lincolnian, CC 2.0)

  • Sean Silverthorne

    Sean Silverthorne is the editor of HBS Working Knowledge, which provides a first look at the research and ideas of Harvard Business School faculty. Working Knowledge, which won a Webby award in 2007, currently records 4 million unique visitors a year. He has been with HBS since 2001.

    Silverthorne has 28 years experience in print and online journalism. Before arriving at HBS, he was a senior editor at CNET and executive editor of ZDNET News. While at At Ziff-Davis, Silverthorne also worked on the daily technology TV show The Site, and was a senior editor at PC Week Inside, which chronicled the business of the technology industry. He has held several reporting and editing roles on a variety of newspapers, and was Investor Business Daily's first journalist based in Silicon Valley.