There is no default or standard margin size for PowerPoint presentations. The appropriate margin size will depend on the size of the slides and the content that you are including in the presentation.As a general rule, it is a good idea to leave enough margin space to balance the content on the slide and create a visually appealing layout. This may mean leaving a larger margin on one side of the slide and a smaller margin on the other side, or leaving the same amount of margin space on all sides.A good starting point is to leave a margin of at least 1 inch (2.54 cm) on all sides of the slide. You can adjust the margin size as needed based on the specific needs of your presentation.To set the margin size in PowerPoint, go to the 'Design' tab and click the 'Page Setup' button in the Page Setup group. In the Page Setup window, you can enter the margin size in the Top, Bottom, Left, and Right fields. You can also use the 'Slide Size' options to adjust the overall size of the slides in the presentation.