What is the WPF Unit?

Answer:

The WPF Unit is measured in DPI.

First we need to understand about DPI and PX (i.e. Device Independent Pixels & Physical Pixels)

1 DPI = 1/96 inch
1 PX = 1/DPI - Depends on screen type
The default system setting is 96 DPI

Note: If the DPI increases, the number of physical pixels which compose one device independent pixel also increases. Hence, objects that have their sizes specified in device independent pixels get larger as the system DPI increases