HOW TO: Change your PowerPoint Presentation page size
PowerPoint has usually worked on a 4:3 size. This is quite rectangular and the size you would have been most familiar with in PowerPoint from versions up to 2016.
The reason for this is that up until more recent years when widescreen became the norm, slides weren’t set up to default to that.
If you are looking to change a screen size from the old 4:3 format to the current formats of 16:9, 16:10 and now the “widescreen” option, you’ll find a quick “how to” below.