A lot of people ask me how many slides they should use in their "PowerPoint deck." That is, how many slides should be used for a single live presentation? My answer these days is "between zero and a thousand."
When I gave my "Art of Presentations" presentation last week at P&G in Kobe (for ACCJ), someone asked me at the end how many slides I had used. So I asked people what they thought. How may slides did I use, I asked (I spoke for 55 minutes). Guesses ranged from 40 to 60. The answer was 285. The audience was at once surprised and amused. Then I asked them, imagine if I had said something like this at the start of my presentation: "Hello, everyone. Thanks for coming. I have 285 slides to go through tonight, so let's get started...." The audience burst out laughing. One man said, only slightly tongue-in-cheek, that he would have ran for the exit doors had I opened that way. And with that, the audience got it: In my presentation, the number of slides was obviously not important. The slides simply supported the talk. People were not conscious of how many slides they had seen or "where I was in the deck."
It's not the slides, it's "the moment"
Once people start counting slides, all is lost. The focus should be on the message and the moment. And "the moment" is a kind of synchronicity among presenter, audience, and supporting visuals that allows the audience and presenter to have a connection that is more like conversation and sharing and less like a didactic stream of bullets, "chart junk," and a ceaseless, incessant "blah, blah, blah" that an audience must endure. A presentation approach which resembles a speaker "getting through a deck of slides" treats the audience like a room full of video recorders. Mutli-media learning theory and cognitive science suggest, however, that this approach is not inline with how people most effectively handle new information. (See this older article, and works by professor Richard Mayer, such as this book).
It's the wrong question
If your audience is conscious of the number of slides you are using — "too many" or "too few" — then that usually means you have inappropriately designed your visuals or are using them in a way that is not helping much. It's not the number that is the problem. I have seen both good and bad presentations that used no more than 10 slides, and I have seen both good and bad presentations that used more than 250 slides. I talked about this idea in my post on the Lessig Method a couple of months ago.
OK, but seriously, how many slides do I suggest? Honestly, it is not something I worry about. There are a million things to worry about, but the size of my "PowerPoint deck" is not one of them. So, maybe the best answer I can give you is to use the "appropriate amount" of visual support. And only you (and your coach if you have one) will know what that is. As John Loori says in The Zen of Creativity, "...make a choice about what's important, and let go of the rest." And the number of slides is not important.
Related Presentation Zen links
Are we asking the right questions?
Should lectures be conversational?