Facilitator Math – When You Need to Use Numbers to Get Better Results


Most facilitators are not really into math, but you may need to be. I keep discovering how important it is to watch numbers and patterns (the underlying structure of math) when you are conducting a facilitated session. 

Here are two quick tips to get really good results.   One is something all facilitators seem to get wrong.  The other is knowing the exact moment to use math to help a group move to converge after they have diverged.  The word “math” may be inappropriate but let’s just say it is important to watch your numbers and the science of numbers.

The Simple Math

What is the easiest way to quickly create groups of the right size?

This a very simple math technique that facilitators always get wrong – even me.  It is about how you count off groups. It requires that you do your math. So here’s the easy rule:  If you want three groups, number each person up to three. Begin again. Three more. If you want four groups count to four; five – count to five, etc.

You also need to know how many people is an optimum number in a small group? I would say a minimum of two and a maximum of five. Some people think it’s fine to have six or seven or eight in a group. I disagree.  People do not have time to share and talk if you have more than five.  The pattern of discussion typically ends up with 3 talking a lot and two others rarely contributing, even in a group of five. Watch this. You will be surprised at how common this is.

Test Question:  If you have 50 people in your room, what number will you count to?

Answer:  You want a maximum of five people in each group. So you count to 10. That way you can have five in each of 10 small groups.

Summary: Count to the total number of groups you want! (NOT the number of people you want in each group)

The Harder Math

How do you know when a group has moved to converge too soon?

Example: The other day we were facilitating a session to help the group reach consensus. We were trying to build consensus around creating buy-in with stakeholders in an efficient way that would also be inclusive and respectful of all the diverse perspectives.

At one point early in the consensus building process, several people in the group suggested merging a few themes. By the way, we were using the ToP consensus workshop method. My internal self-facilitator talk was saying  “danger, danger”. I knew there was something wrong with that suggestion yet I wanted to honor the group that was suggesting it.  I realized later that it was much too early to merge themes. We really were still in the divergence process and people were trying to converge too early. However, I didn’t know how to articulate it. In retrospect, I realized it was the math that tipped me to the danger!!  There were too few groupings with too few ideas in them. We had four groupings, many with only two ideas in them. It was too soon because we would lose the richness of the conversation on the ideas, and also the depth of the eventually converged themes.

In the ToP methodology, the math suggests we wait until we have at least five or six small groups of ideas (generally with 2-3 ideas in each). Once we have these five or six themes, it works quite well to go into the convergence process. We add more, but similar ideas, to the existing groupings.  What the ToP methods have figured out is that with 25 to 45 ideas, you’re probably going to end up with with 5 to 7 good themes. But you need to allow the process to unfold slowly. You need people to really hear each other, clarify their ideas, discuss them, and only then begin to add in their remaining ideas. Ensure you have a rich discussion that clarifies ideas and builds relationships between ideas before converging too much. Then, as convergence begins, each participant will realize how new ideas fit with other group’s ideas. And, they will gladly and confidently see how their “new” ideas relate to existing groupings.

That is the process of building consensus and that is the math – there are almost always 5 to 7 themes. Anything above that number is fine but not necessarily needed. Anything below that means the data won’t be as rich and/or as specific as you need it to be. Now that’s facilitator math.

Question 1:  How many grouping do you need to get the wisest, richest results?

Answer 1: Generally, ICA who created ToP methods, says that 5-7 themes  will yield all the most important key ideas there are on that topic.

Question 2:  How many ideas should you ask the group to brainstorm for the richest, most well-rounded product?

Answer 2: Generally, ICA says that 35-45 ideas for any size group will yield all the most important themes there are on that topic.

What other ways have you discovered math or patterns to be important in facilitation?

Barbara MacKay

Barbara loves “everything facilitation”. She thinks BIG! She loves working with other facilitators around the globe to create transformational results for client groups. She loves teaching others how to do that. She loves presenting at global facilitator conferences. She loves certifying new professional facilitators. If you also love what process facilitation can do for the world, connect with her – virtually or in person. She believes facilitation processes, used well, will provide the roadmap to a more just and sustainable world.


  1. Jo Nelson on December 11, 2019 at 12:55 am

    There is research that says that the human brain holds “7 plus or minus 2” things at a time. So that indicates that 5-9 clusters are probably optimal. if you start with at least 4 pairs before adding new cards to a cluster, you will almost always end up with 5-9 clusters, and surprisingly usually 7.

    My experience is that between about 35 and 60 diverse ideas are enough to ensure validity — more than 60 cards, no matter how large the group, are mostly overlap. I don’t know of any research except my own experience that demonstrates this, however!

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