Room Area Calculator

Room
Room shape
Columns and other obstructions inside the room

No items yet.

Doors and windows
Doors and windows
#1
#2

Enter the room's internal (wall-to-wall) dimensions. The floor area is the geometric area of that outline; an official (cadastral) floor area is measured to its own rules and can differ. A column inside the room cannot be cut out of the shape (an outline with a hole is rejected) — enter it under "Columns and other obstructions inside the room" instead.

Every door and window is deducted from the wall area at its full size. Some trades (for example painting) deduct only larger openings — check the convention your contractor uses.

Diagram
Floor area20.00m²
Wall area (less openings)44.46m²
Room volume54.00m³
Floor and ceiling
Floor area20.00 m²
Ceiling area20.00 m²
Perimeter18 m
Perimeter less door widths (skirting length)17.1 m
Walls
Wall area, gross48.60 m²
Doors and windows4.14 m²
Wall area, net44.46 m²
Volume
Room volume54.00 m³

About this calculator

This room area calculator works out the floor area of a room in square metres, its perimeter, the wall area less doors and windows, the ceiling area and the room volume in cubic metres. Pick the room's shape — rectangle, L-shape, alcove, T- or U-shape, or a custom outline built from rectangles — enter the wall lengths and the wall height, then list the doors and windows.

Use it to order floor coverings, paint, wallpaper or plaster, or to size heating and ventilation by the room volume.

Formula

room area    = area of the room outline (added rectangles less cut-outs)
floor area   = room area − Σ (column width × depth × count)
ceiling area = floor area                      (flat ceiling)
perimeter    = sum of the wall lengths
wall area    = perimeter × wall height − Σ (opening width × height × count)
volume       = floor area × wall height
column faces = Σ 2 × (width + depth) × count × wall height   (reported apart)
skirting     = perimeter − Σ (door width × count)

Worked example

A 5 × 4 m room, 2.7 m high, with one 900 × 2100 mm door and one 1500 × 1500 mm window:

floor area = 5 × 4                 = 20.00 m²
perimeter  = 2 × (5 + 4)           = 18.0 m
walls      = 18 × 2.7              = 48.60 m²
openings   = 0.9 × 2.1 + 1.5 × 1.5 = 4.14 m²
net walls  = 48.60 − 4.14          = 44.46 m²
volume     = 20 × 2.7              = 54.0 m³
skirting   = 18.0 − 0.9            = 17.1 m

FAQ

How do I calculate the area of an L-shaped room? Choose the L-shape and enter the overall length and width and the size of the missing corner; the calculator takes the corner off. Any other shape can be built from rectangles in the custom mode.

Should I deduct doors and windows from the wall area? For materials that do not go over the openings (paint, plaster, tiles) — yes. Some trades deduct only openings above a certain size, so check your contractor's convention.

How do I enter a column in the middle of the room? Under columns and other obstructions, with its width, depth and count. A column cannot be cut out of the room shape itself — an outline with a hole in it is rejected — so it is entered separately and taken off the floor, the ceiling and the volume. Its faces are listed apart, for painting or plastering.

Is this the same as the official floor area? Not necessarily. This is the geometric area of the internal outline you enter. An official (cadastral) area is measured to its own rules, for example about wall recesses, low ceilings and fixed equipment.

Which standard does this follow? None — the results are plain geometry of the outline you enter.

Assumptions and limits

  • The room shape is one outline without holes; interior columns are entered separately.
  • Walls are at right angles and all the same height; the ceiling is flat (no slopes or beams).
  • Dimensions are internal, wall face to wall face.
  • Openings are deducted at their full size; reveals are not added.
  • The skirting length takes off the door widths only; it does not add or remove anything for corners.