Quantities
Wall area less openings
- where
- gross wall area (m²)
- length (m)
- height (m)
- net wall area (m²)
- total openings (m²)
Explain this equation
This gives the area of one flat wall face, before and after taking out windows, doors and other openings. It is usually the first step in pricing or ordering bricks, blocks or mortar for a wall.
l is the length along the wall and h is its height, so l × h is the whole rectangle of the face, A_gross. A_o is the combined area of every opening in that face, entered as one total. A_net is the brickwork actually laid.
A rectangle's area is simply length times height, and the openings are holes in it, so they are subtracted. Everything is in metres, so the answers come out in m².
A 5 m wall 2.4 m high is 12 m² gross; take out a 2 m² window and you lay 10 m². Doubling the length doubles the gross area, but the openings stay the same, so the net area more than doubles.
Watch out: reveals, returns and recesses are extra surfaces and are not included. The calculator stops if A_o is larger than the gross area.
Measure one flat wall face and deduct the combined area of its openings.
Enter your values to see the result.
Good to know
Enter the total opening area once. Reveals, returns and recesses are separate surfaces.
Sources
- Geometry / arithmetic
Estimates are not design approval or British Standards compliance checks. Structural arch, retaining-wall, wind, foundation, lintel and masonry-capacity design are not performed. Use the project engineer’s specification.