Elevation math
Add walls and gables, then handle openings deliberately
Measure each unlike elevation separately. Rectangular wall area is width × height. A triangular gable is base × vertical gable height ÷ 2. Add the sections, subtract the openings you intend to deduct, and record the gross and net areas so the decision stays visible.
net area = rectangular walls + triangular gables − deducted openings
adjusted area = net area × (1 + waste ÷ 100)
Worked example
A 30 × 10 ft wall with 40 ft² of openings
The wall has 300 ft² of gross area. After subtracting 40 ft² of entered openings, net area is 260 ft². With a user-selected 10% allowance, adjusted coverage is 286 ft².
One siding square represents 100 ft², so 286 ft² is 2.86 siding squares. That coverage figure is not necessarily the number of cartons or panels sold by the selected manufacturer.
Product conversion
Square footage is only the first purchase step
Panel exposure, overlap, usable coverage, package size and accessory systems vary. Use the general siding calculator for area and squares. Enter exact coverage per piece only when supplied by the product documentation; use the vinyl-specific calculator when panel length and usable exposure are known.
Starter strip, corners, J-channel, utility trim, flashing, fasteners, weather barrier, course layout and installation clearances require the chosen system's instructions.
Sources
References and project authority
These references support the stated measurement convention or planning boundary. Product instructions, the approved design, and local requirements take priority for the actual project.
- Vinyl Siding Institute installation manual documents rectangle/triangle takeoff methods, project-specific waste and the 100 ft² siding square.