As a PowerPoint add-in developer you will often have to control a setting for a shape (for example, the size).
However, the UI gives a shape size in inches, while when setting programmatically you have to work with PowerPoint units.
A PowerPoint unit is actually 1/72″, meaning it is a “PostScript point” (see typography units for more information).
To quickly convert from inches to points, use the following formulae:
size_in_points = size_in_inches x 72