Keep the presentation about you, not the slideshow. [2] X Research source The slides are there to support what you have to say. They should be just one part of your presentation, not the whole thing.
Go through your entire presentation and ask yourself if you really need a given slide. If the answer is no, or if you find you can deliver the info verbally instead, eliminate it.
If your presentation ended well before the time limit you’ve been given, try to extend the amount of time you spend on each slide, or add extra slides to expand on the info introduced in the presentation. Solicit advice from family and friends during your practice presentation. If they feel there are too many or too few slides, or if they feel certain sections of the presentation felt rushed or slow, adjust your presentation to correct these deficiencies.
One well-known formulation for PowerPoint presentations is the 10/20/30 rule. This rule dictates that you should use about ten slides for a twenty minute presentation, and each slide should utilize thirty point font. In other words, each slide should be about two minutes in length. [8] X Research source Perhaps the 10/20/30 rule works for you. If it does not, don’t feel as if you’re using the wrong number of slides. Others argue that an average slide should be onscreen for no more than two minutes, and can be onscreen for as little as 15 seconds. [9] X Research source
If, on the other hand, you’re in a more intimate environment and can control the lighting, you might be inclined to utilize a greater number of slides. As always, however, don’t feel obligated to use many slides just because you can.