#203 – Window Size and Location Are Specified in Device Independent Units

The Window class has Left and Top properties that specify the location on the screen of the left and top sides of the window.  It also has Width and Height properties that specify the window’s size.  All of these are expressing in device independent units.

If the current DPI setting is 96 dpi (dots per inch), the WPF units are equivalent to pixels.  I.e. A window specified as 96 units high would appear as 1 inch high.  If the DPI setting is different, the specified WPF units are scaled by dpi/96 to get the resulting pixel value.

In other words:    # pixels = (# WPF Units) * (DPI / 96)

The reason for this is so that WPF applications will appear at roughly the same dimensions on various monitors, regardless of the pixel density.