I know because I measured it. 42"x54". It seems that I clean house the same way I fight battles in Axis&Allies: work my way into a corner then fight my way out, keeping the perimeter as short as possible.

The thing is, counterintuitive as it may seem, cleaning gets progressively more difficult as I proceed. The reason is actually quite simple: there is very little trash in the apartment; it's all
stuff, all quite useful. Now comes the fun: the
stuff:space ratio is astronomically high. Contrary to some opinions, simply stacking the
stuff doesn't work; one needs to be able to
access the
stuff. With this in mind, the
stuff:space ratio must always be less than unity; it can creep a little higher as you find wall space from which to hang
stuff, but you still need to be able to get at the
stuff, so it really can't get up to the ceiling.
At this rate, then, I should come close to finishing Spring Cleaning 2007 by autumn 2009. C'est la vie.