You can quickly learn the square footage of a room in AutoCAD.
First, make sure your endpoint Object Snaps are on. To turn on your OSNAPS, right click on the OSNAP Button at the bottom of the screen, this brings up the settings box. Check the box next to ENDPOINT and check OBJECT SNAP ON. Close this box by clicking OK.
Now to find a room's square footage, type AREA on the COMMAND LINE, then click on each corner of the room. Click on each corner in order and be sure to re-click the first corner you clicked on. Press ENTER. On the command line, AutoCAD will tell you the SQUARE FOOTAGE, SQUARE INCHES, AND PERIMETER.