I remember in grad school, for school assignments, teachers will require a set number of slides as part of grade elements. Many people whose only reference is that experience often complain about high slide counts in presentations. How many slides is too much? How does one go about deciding the right number to include in a presentation? Are there rules which will make this decision an easy one?
Unfortunately, there are no fast rules when it comes to the number of slides in a presentation. It depends on the duration of the presentation, the degree of details you wish to share, and your familiarity with the guidelines of a powerful presentation. Let’s examine the problem with too few slides.
Too few slides
The first problem with the concern over slide count is the density of information crammed into one slide. Too much information on a single slide forces the presenter to use the slide as a crutch. The brain activity required to remember all the points on the slide proves overwhelming. To avoid cognitive overload, it’s very common to see some presenters carry around notes. While not a big problem, paper notes can take the audience away from the main message.
Further, too much information on the slides keeps the presenter from telling his story. Information density is a problem not just for the presenter but also for the audience. Research has shown that when given the option, the brain will always elect to tackle the easiest task available. In this case, it’s much easier to read the slides than to read the slides and listen to the presenter at the same time. Adding too many slides also creates its own troubles.
Too many slides
The primary issue with too many slides is the display speed. To cover the information on all the slides, the presenter will have to go fast. This leaves the audience too little time to capture, let alone retain, the information presented. The frantic pace of the presentation denies the audience the opportunity to learn with the presenter. Too little is a problem, and too many is also a problem. So how do we get to the right number of slides?
My approach
My preferred formula is to not spend more than two minutes on a slide. So if the presentation will last an hour, my deck will have approximately 30 slides. I found this to be a comfortable pace for an effective presentation. However, there is a significant caveat. For this approach to work, the presenter has to invest a lot of time not only in deciding what kind of information makes it onto the slides but also in what kind of information will better serve the story in the speaker notes.
Clearly, there is an answer to the slide problem that seems to work pretty well for most speakers. Too few slides and you end up with high information density problem; too many and you create an information dissemination speed problem. Either one means that the audience has to work much harder to retain the information. A high cognitive load pushes the audience to stop trying to retain information. Great presentations have an easy flow, and the story these presentations tell is in sync with the visuals. That’s the only way to ensure a comfortable audience experience.
