Calculate the net paintable or plasterable wall area after deducting doors and windows - useful for the Paint Calculator, Sand Calculator, or ordering materials accurately.
Doors
Windows
How to Use the Wall Area Calculator
Enter the "Wall Length", "Wall Height", and "Number of Walls" (if they're identical).
Enter the "Number of Doors" and their width/height - defaults are for a standard door.
Enter the "Number of Windows" and their width/height - defaults are for a standard window.
Click "Calculate Wall Area" to see the gross area, total deductions, and net paintable/plasterable area.
How the Net Area Is Calculated
Gross area = Wall length × Wall height × Number of walls.
Deductions = (Doors × door width × door height) + (Windows × window width × window height).
Net area = Gross area − Deductions. If the openings add up to more than the wall, the net area is shown as zero.
All doors are assumed to be the same size, and so are all windows. If a room has a large main door and a small bathroom door, run the calculation with one door size and subtract the difference for the other, or work out each opening by hand.
Worked Example: A Room With Unequal Walls
A living room is 4 m by 3.5 m with a 3 m ceiling. Because the walls are not all the same length, enter the perimeter as a single wall: 2 × (4 + 3.5) = 15 m as the length, 3 m as the height and 1 as the number of walls. Gross area = 15 × 3 = 45 m².
The room has one 0.9 × 2.1 m door (1.89 m²) and two 1.2 × 1.2 m windows (2.88 m²). Deductions = 4.77 m², so the net wall area = 40.23 m², which is about 433 sq.ft.
Entering the perimeter as one long wall works for any room shape made of straight walls, including L-shaped rooms, as long as the height is the same throughout.
Typical Opening Sizes in Indian Homes
Opening
Typical size
Area
Bedroom or internal door
0.9 × 2.1 m
1.89 m²
Bathroom door
0.75 × 2.1 m
1.58 m²
Main entrance door
1.0 × 2.1 m
2.10 m²
Standard window
1.2 × 1.2 m
1.44 m²
Wide window
1.5 × 1.2 m
1.80 m²
Bathroom ventilator
0.6 × 0.45 m
0.27 m²
Actual sizes vary between builders, so measure your openings if you need a precise figure.
Measuring Tips and Unit Conversions
Measure height from the finished floor to the ceiling, or to the underside of a cornice or false ceiling if the wall above it is not being finished.
The calculator works in metres. To convert a tape reading in feet, multiply by 0.3048; a 12 ft wall is 3.66 m and a 10 ft height is 3.05 m.
Painters and plasterers in India usually quote rates per square foot. Multiply the net area in m² by 10.764 to get square feet.
For painting, the net area here covers walls only. Add the ceiling (room length × width) separately if it is part of the job.
Wardrobes, kitchen cabinets and tiled dados cover wall that will not be painted. Treat them like openings and subtract their area.
A contractor's measured area can differ from this figure. Measurement rules commonly used in Indian building contracts, such as those in IS 1200, often ignore small openings and add the sides (jambs) and sills of larger openings rather than simply subtracting the opening. Ask how the area will be measured before agreeing a per-square-foot rate.
Frequently Asked Questions
Doors and windows aren't painted or plastered the same way as the wall surface, so subtracting their area gives you a more accurate estimate of materials needed - over-ordering paint or plaster wastes money.
This calculator assumes identical walls for simplicity. For rooms with different wall sizes, calculate each wall separately and add the net areas together.
Yes, if a wall has no doors or windows, just leave those counts at 0 and the calculator will use the gross area as the net area.
Yes. The net area is the same starting point for paint, putty, plaster and wall tiles. Each material then applies its own allowance: for example, tiles need extra for cutting and breakage, and plaster quantity also depends on its thickness.
Split it into a rectangle and a triangle. Calculate the rectangular part with this tool, then add the triangle separately as ½ × base × height, and enter or add up the results by hand.