The distances can be meassures in pixel (default), cm or inch.
For cm and inch, you have to edit the monitor size in the options window.
The angles can be meassured in degrees [0..359] (default) or radiant [0..2*PI].
This screenshot shows you a typical view of MB-Ruler, where the basic functions are explained.
A click with the right mouse button on the MB-Ruler symbol in the TNA opens a popup menu
with the options menu item.
In the options window, you can modify the size of the ruler, its color, the distance and angle unit
your monitor size and the angles, to which the ruler should snap, when you rotate it.