I don't know of any site but the size of the rooms are the same a studio is about 355 sq ft, one bedroom 725, two bedroom 1080, these are give or take a few feet. The only difference is OKW that dwarfs the others with studio 390, one bedroom 1005, two bedroom 1410 and the GV 2375 with BW GV at 2142.
Here are room sizes for DVC Resorts according to the Disney Travel Industry Reference Guide and DVC Public Offering Statements. I think Disney does use averages for these sizes, as some rooms do vary a little. These numbers will provide a good basic reference though.
Old Key West
Studio 390 sq ft
1-Bedroom 1005 sq ft
2-Bedroom 1410 sq ft
Grand Villa 2375 sq ft
Villas at WL
Studio 356 sq ft
1-Bedroom 727 sq ft
2-Bedroom 1080 sq ft
Boardwalk Villas
Studio 359 sq ft
1-Bedroom 712 sq ft
2-Bedroom 1072 sq ft
Grand Villa 2142 sq ft
Beach Club Villas
Studio 356 sq ft
1-Bedroom 726 sq ft
2-Bedroom 1083 sq ft
Saratoga Springs Resort & Spa
Studio 356 sq ft
1-Bedroom 726 sq ft
2-Bedroom 1083 sq ft
Grand Villa 2145 sq ft
Hilton Head
Studio 455 sq ft
1-Bedroom 856 sq ft
2-Bedroom 1311 sq ft
Grand Villa 2362 sq ft
Vero Beach
Inn Room 360 sq feet
Studio 375 sq ft
1-Bedroom 880 sq ft
2-Bedroom 1265 sq ft
Beach House 2125 sq ft