The size of a PowerPoint file can quickly increase as you start adding graphics. The next thing you know, your presentation is several megabytes in size. If you need to decrease the size of the file, there are a few things that you can try.
First, if you don’t need to print the presentation, try reducing the resolution of all graphics to 96 DPI. The graphics will still look clear on screen.
Second, if any of the graphics are bitmaps (.bmp), convert them to .jpeg or .png. Bitmap images are typically larger than other file formats and likely a contributor to a large file size.