Calculate My Home
Units

Room Square Footage Calculator

Enter the room, add closets and bays or cut out corners, and get floor, wall and ceiling square footage plus the perimeter.

Units
Room length
ft
in
Room width
ft
in
Ceiling height
ft
in

For wall area. A standard ceiling is 8 ft.

Closets, alcoves, bays and cut-outs

  • Closet

    It
    Width along the wall
    ft
    in
    Depth out from the wall
    ft
    in
Doors and windows (for wall area)
Door width
ft
in
Door height
ft
in
Window width
ft
in
Window height
ft
in

Enter a length, width and height above zero, and a size for every closet, bay or cut-out.

A room's square footage is its length times its width, plus any closet or bay that opens off it, minus any corner the room gives up. A 14 × 12 ft bedroom is 168 sq ft; add a 6 ft wide, 2 ft deep closet and the floor is 180 sq ft. With an 8 ft ceiling the walls come to 404 sq ft after one door and two windows, and the ceiling matches the floor at 180 sq ft.

How the room is calculated

The calculator starts from the main rectangle and adjusts it for every part you add.

Floor = length × width + each addition (width × depth) − each corner cut-out (width × depth)

The perimeter follows the walls. An alcove or closet adds its two side returns, 2 × its depth, because its back wall replaces the stretch of wall it opens from. A corner cut-out, such as a chimney breast or a stair box in the corner, leaves the perimeter unchanged: the two short walls it creates are exactly as long as the two pieces of wall it removes.

Walls = perimeter × ceiling height − doors − windows · Ceiling = floor (flat ceiling)

Worked example

The calculator opens with a 14 × 12 ft room, an 8 ft ceiling, a 6 × 2 ft closet on one wall, one 3 ft × 6 ft 8 in door and two 3 × 4 ft windows.

  • Main floor: 14 × 12 = 168 sq ft
  • Closet: 6 × 2 = 12 sq ft, so the floor is 180 sq ft
  • Perimeter: 2 × (14 + 12) + 2 × 2 = 56 ft
  • Gross walls: 56 × 8 = 448 sq ft
  • Openings: 3 × 6.67 = 20 sq ft for the door, 2 × 3 × 4 = 24 sq ft for the windows
  • Net walls: 448 − 44 = 404 sq ft
  • Walls and ceiling: 404 + 180 = 584 sq ft

The plan under the result is drawn to scale: the main room solid, additions dashed outside the wall they open from, and cut-outs hatched inside their corner.

Square feet of a room with a closet or bay window

Measure the closet opening wall to wall, then from the room's wall line to the back of the closet. A bay window counts the same way if its floor is level with the room: a 5 ft wide bay that projects 2 ft adds 10 sq ft of floor and 4 ft of perimeter. Several additions on one wall are fine as long as their widths together fit along it.

Rooms with a missing corner

A corner cut-out handles a room that is an L-shape or has a boxed-in corner. Taking a 3 × 3 ft corner out of the 14 × 12 ft room leaves 168 − 9 = 159 sq ft of floor, and the perimeter stays at 52 ft. For a room shaped like a triangle, a circle or an irregular polygon, the square footage calculator has those shapes and a room list that adds several rooms together.

Walls and ceiling for paint and drywall

Floor area buys flooring; walls and ceiling buy paint and drywall. Take the net wall area to the paint calculator, which turns it into gallons, and the walls plus ceiling to the drywall calculator, which turns it into sheets. When you hang drywall, many installers board right over small openings and cut them out afterwards, so use the gross wall figure there if that is how you work.

Doors and windows default to common sizes, 3 ft × 6 ft 8 in and 3 × 4 ft. Measure your own: a 6 ft sliding patio door takes out almost twice the wall of a standard door.

Perimeter for trim and baseboard

The perimeter is what you run baseboard, crown and wall-to-wall carpet tack strip along. Subtract each door width for baseboard: the example's 56 ft less one 3 ft door leaves 53 ft. The baseboard calculator turns that length into pieces to buy.

Floor area for flooring and heating

Buy flooring for the floor area plus waste in the flooring calculator; closets are usually floored with the room, so leave them in. For sizing a heater or air conditioner the BTU calculator starts from the same floor area and adjusts for ceiling height, windows and climate.

Measuring tips

  • Measure at floor level, wall to wall, and round to the nearest inch. The calculator takes feet and inches directly: 12 ft 7 in, not 12.58.
  • Measure both long walls. If they differ by more than an inch the room is out of square; use the longer figure for buying material.
  • Leave out cabinets and fixed tubs only when you are buying flooring that stops at them. Most floating floors do; tile often runs under a freestanding tub.

All measuring tools, from volume to moving boxes, are gathered in the measuring and planning calculators.