PowerPoint allows users to zoom in and zoom out of the slides to help focus on specific sections or look at the entire slide as a whole. The minimum zoom supported by PowerPoint is 10% and the maximum is 400%. The zoom bar is located in the bottom right corner of the PowerPoint window.
To change the zoom settings from the zoom bar, you can click on the marker and drag it. Dragging to the left will zoom out and to the right will zoom in.
Alternately, you can click on the zoom percent to open the zoom dialog. Here you have the option to auto-fit the slide in the screen, or choose from six pre-defined zoom settings, or define your own zoom setting.