100 square feet is clear in what it means. It is an area which could, for example, be a 10' x 10' square, a 20' x 5' rectangle or a right-angled triangle where the short sides are 20' and 10' long. 100 feet squared could be the same, but sometimes means a square with 100' long long sides (and an area of 10,000 square feet).
The floor of the kitched is 30 square foot in size Obviously square feet is the grammatically correct option but square foot is also commonly used and is, I guess, one of those instances where, despite being technically wrong, it has entered into common usage to such an extent that it is sort of accepted.
In English, we abbreviate: feet = ft inches = in square inches = sq in cubic feet = cu ft ounces = oz gallon = gal quart = qt I know the words pies, pulgadas, cuadrados, cúbicos, onzas, galón, cuarto, but what are the abbreviations in Spanish? Since these are American measures, can I...
However, as reference points, the standard square blocks of Portland, Houston, and Sacramento are 260 by 260 feet (79 m × 79 m), 330 by 330 feet (100 m × 100 m), and 410 by 410 feet (120 m × 120 m) respectively (to the street center line). Oblong blocks range considerably in width and length.
"Our biggest challenge is making sure we can cover our "nut" (lease, utilities, insurance, equipment, etc.) for our 4200+ square feet facility without totally killing ourselves."
Yahoo: How Big Is 100 Square Feet? 14 Real Homes Illustrate What It's Like