When is a door not a door?

If I'm doing something that I'm fairly confident about, that's probably the easiest time to confuse me. As part of my fantasizing about interior decorating phase, I measured my bedroom (including door, closet, and windows) and drew a scale diagram. Then I checked it, discovered that the door was not 36" wide but only 30" wide (apparently, 36" is the standard width of only outside doors, and 30" is the standard width for interior doors). So, then, why was the wall with the door the same length as the opposite wall? It should've been 6" longer.

I drew my living room diagram, and everything there seemed okay. I remeasured everything in my bedroom and living room again. The living room checked out, so I don't need to redraw it, and I discovered the error in the bedroom. Yay!

It turns out I had a built in fudge factor. My assumption that the door was flush with the side wall was incorrect. It turns out that it is 6" away from the wall. This, surprisingly and almost miraculously, is exactly the difference in assumed door width and actual door width. I could just erase that corner of the drawing and draw the correct dimensions -- if I hadn't already inked the drawing. (It figures, since I hadn't inked the living room drawing, which was correct.)

Lesson learned: double check your sketch before you finalize it.