Assuming that the room is 12 FEET by 28 FEET the area is 336 square feet.
Just multiply the two numbers to get square feet. This will give you 336 square feet.
336
400 square feet.
16' x 15' = 240 square feet.
A room that is 12 feet by 13 feet is 156 square feet in area
187 square feet.
360 square feet.
400 square feet.
525 square feet.
120 square feet.
252 square feet.
324 square feet.
140 square feet.
352 square feet.
130 square feet.
770 square feet.
240 square feet
300 square feet.
162 square feet.