@Vica
Excuse me.
You're right.
To make the calculation correct, it's essential to include the screen resolution in the equation. AutoCAD's system variables only refer to the dimensions of the drawing area.
Therefore, my previous formula could only be approximate.
If you want to calculate the cursor dimensions exactly, you need to obtain the screen resolution.
To do this, you can use this function
(defun AnchoResol (/ s i is)
(setq s (vlax-invoke (vlax-create-object "WbemScripting.SWbemLocator") 'ConnectServer nil nil nil nil nil nil nil)
is (vlax-invoke s 'ExecQuery "SELECT CurrentHorizontalResolution, CurrentVerticalResolution FROM Win32_VideoController")
)
(vlax-for i is (vlax-get i 'CurrentHorizontalResolution))
)