Any slides you use during your presentation should serve as a stage-setting or backdrop; they should rarely be the sole focus for the message. You deliver the message, not the slides. People can only process one inbound message at a time. They will either listen to you or read your slides; they cannot do both.
When you open a slide application to create a new slide, the default format you’re offered is appropriate for a report. If you fill the default master template with words, it will take your audience twenty-five seconds to read the slide. Since they can’t read and listen at the same time, if you have forty slides multiplied by twenty-five seconds, they’ll be reading for over sixteen minutes of your presentation, instead of listening to you.
By planning the structure first, you can ensure the presentation won’t go too long. Audiences squirm when a frustrated presenter delivers for fifty-five minutes and then says, “Oh man, where’d the time go, I still have forty-three slides, so hang on, I’ll get through them in the next five minutes.” If you plan a solid structure with the timeframe in mind, it guarantees you will stay within the time constraints.
What’s the right number of slides? There is no definitive “right number” of slides for a presentation. It’s all driven by the personal delivery and pacing of the presenter. So the answer is “as many as necessary to get your point across.” Hollywood scene and story analysts adhere to the practice of making scenes no longer than three minutes for fear of losing the audience’s interest. Three minutes! Odds are high that your audience is losing interest every three minutes too, and to compound the problem, you don’t have a $100 million blockbuster movie budget. Because the presentation medium is more static than cinema, don’t stay on a slide for any more than two minutes. Changing the visuals as often as possible helps regain audience attention.
Most presentations have multiple points per slide and are a document, not a slide. If you choose to put only one idea per slide, you’ll have more slides than are traditionally seen in a slide deck that makes multiple points-per-slide.