Every time this “slide” question comes up in our presentation skills workshops, I’m tempted to counter with this question: “How much does a house cost?”
Impossible to answer except in a general sense: “Far fewer than most people use.”
The asker probes, “But as a rule-of-thumb, how many—one per minute? One per three minutes? Thirty in an hour’s presentation?”
Still impossible to answer. For a 10-minute overview to a conference, you may need none. For a 20-minute sales presentation, you may need six. For a 60-minute motivational keynote, you may need six. For a 7-hour safety training session, you may need 160.
Your decision should flow from the answers to these three key questions:
- Do I need visual support here on this point to make the message clear?
(If it would be difficult for the audience to follow what you’re saying without a photo or drawing, add a slide.)
- Would a visual help me make this point more quickly than words alone? (If the information is complex and a chart rather a long explanation would simplify, add a slide.)
- Would a visual make this point more memorable? (A great analogy or scene depicted on the visual may have stronger impact than your words alone.)
Precautions to keep in mind as you develop slides:
- Don’t treat your slides as your notes. Some presenters use their slides as notes and prompts for “what comes next.” Instead, use a speaking outline of your presentation.
- Rehearse your presentation with your slides. Slides add length. If you show a slide, you need to pause long enough for the audience to absorb it. If you simply talk over it, the visual competes with you for the audience’s attention. Even if you simply display a photo, the audience needs a few seconds to take it in. If it’s a humorous slide, you need to pause for laughter. Timing will vary from slide to slide, depending on whether you’re showing a photo or a technical diagram.
- Vary the pace of your slides. That is, you’ll bore the audience to death if you show a slide every 1.5 minutes.
- Keep in mind that YOU are the presentation, not your slides. Visuals should support, not sabotage, your presentation.
The biggest tip in getting the right number of slides: Don’t open PowerPoint (or whatever presentation software) and use your slides to generate ideas and outline your talk. Instead, plan your talk first. Then circle back and decide where you need visual support. You’ll end with far fewer slides than you if you “reverse engineer” the presentation.
The fewer the slides, the stronger the impact.