WPF analogy for 'em' unit

em size is the width of the uppercase letter M in the current font, there is no font-dependent sizing method in Wpf

Btw, WPF uses "device independent pixels" that are always 1/96 of an inch (because that's one pixels on today's monitors) so:

• 1 pixel is 1/96 inches
• 96 pixels in an inch
• 1.33333 pixels is a point
• 3.779 pixels is a mm

Those are extremely inaccurate on monitors because almost all monitors report a 96DPI resolution and ignore the real pixel size, but are very useful when printing.