M0710NM4N

Is there no way to draw walls with interior measurements in mind? Lets say I want to create a room with interior dimensions of 20' x 20'. If I draw 4 walls to create the room using 20' walls the interior dimensions aren't 20' x 20' because of how the corners connect and would then have to take into account the wall thickness. Maybe have corner walls draw on the exterior rather than the interior or something to make it easier?