How to Calculate Wall Area If You Know Floor Area

Square Room

• 1

  Take the square root of the floor area to get the width of one wall in a square room. If the area is 100 square feet, for example, the width of one wall is 10 feet.

• 2

  Multiply the wall width by four to get the perimeter of the room. For a wall width of 10 feet, the perimeter is 4 times10 feet equals 40 feet.

• 3

  Multiply the perimeter of the room by the ceiling height to get the wall area. If the perimeter is 40 feet and the height is 10 feet, multiply 40 times 10 feet to get a wall area of 400 square feet.

• 4

  Subtract 20 square feet for each standard door and 15 square feet for each standard window from the total wall area if you need the area without doors and windows.

  Measure the width and height and multiply together for non-standard doors and windows, then subtract the calculated area from the wall area.

Round Room

• 5

  Divide the floor area by 3.14 and take the square root of the result to find the radius of the room. If the area is 100 square feet, for example, the radius is 5.64 feet.

• 6

  Multiply the radius by 6.28 ( 2 pi) to find the perimeter of the room. If the radius is 5.64 feet, the perimeter is 6.28 times 5.64 feet equals 35.42 feet.

• 7

  Multiply the perimeter by the ceiling height to find the wall area. If the perimeter is 35.42 feet and the height is 10 feet, the wall area is 354.2 square feet.

• 8

  Subtract 20 square feet for each standard door and 15 square feet for each standard window from the total wall area if you need the area without doors and windows.

  Measure the width and height and multiply together for non-standard doors and windows, then subtract the calculated area from the wall area.