There are 12 inches in one foot. Therefore, 21 inches is equal to 21/12 = 1.75 feet.
21 inches equals how many feet?
It is 2.1875 square feet.
I assume you mean a rectangle. You can:* Convert everything to feet, then multiply; or: * First multiply, then divide the result (which is in square inches) by 144, to convert to square feet.
Divide the inches by 12 for your answer: 6 feet, 4 inches.
28 inches 2.3333333333 feet.