this is a video on youtube talking about WOW.
i know, WOW, who cares..... BUT
go to the 3:00 minute mark and watch for 30 seconds.
they are talking about the size of WOW if it where a real land mass, then all of a sudden the guy drops a UO reference, kinda took me off guard.
Adding up all the over world in each facet, which doesn't account for dungeons or whatever is underground the entire world (Tram, Fel, Lost Lands, Ilsh, Malas, Tokuno, and SA) comes in just over 20.5 square miles, or 55.9 square kilometers. These are using rough measurements as well, since some of the areas aren't perfectly square.