Construction
Wall Area Minus Openings Calculator
Find net paintable or coverable wall area by subtracting doors and windows from gross wall area.
The result shows the gross wall area and the net area after openings; the net area is the surface that actually needs paint or covering.
Formula
Gross wall area = length multiplied by height. Net area = gross area minus total area of doors, windows and other openings.
How it works
Measure the wall's length and height, then subtract the combined area of every door, window and opening in it. The net figure is what paint, wallpaper or cladding actually needs to cover, so it avoids over-ordering.
Worked example
For example, a wall 5 m long and 3 m high has a gross area of 5 × 3 = 15 sq m, and after subtracting 3 sq m of openings the net area is 15 − 3 = 12 sq m.
FAQs
How do I total the openings?
Measure each door and window, multiply width by height for each, and add them all together.
Should I subtract skirting or trim?
No, those are small compared with the wall and are usually ignored for coverage estimates.
What about several walls?
Calculate each wall separately and add the net areas for the room total.
Rough estimate only — consult a licensed professional for structural work before building.
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