Question: how many square feet is 12x15?
Answer: Area of the floor or ceiling: Multiply the length by the width (10 feet x 12 feet = 120 square feet of area). Area of a wall: Multiply the width of the wall by its height. So one of the walls is 80 square feet (10 feet wide x 8 feet high) and the other is 96 square feet (12 feet x 8 feet).