Squares, the siding unit
Like roofing, siding is ordered in squares of 100 square feet. The calculator takes the wall perimeter × height, subtracts doors and windows, and converts to squares with a 10% waste allowance for starter strips, corner trims and the cuts around every opening.
Gables and stories change the math
Triangular gable ends add roughly half their base × height each — measure them separately and add. Two-story houses save money per square foot because the wall is continuous, but require staging: scaffolding rental is a real line item that scales with height, not area.
Sources and standards
Where these figures come from
Every formula on this page is implemented from the published reference material below. Where a value depends on a regional code, the calculator lets you override it rather than assuming one jurisdiction.
- Brick Industry Association — brick counts per square foot and mortar coverage rates.
- Vinyl Siding Institute — installation standards and product performance certification.
Figures, formulas and reference tables last verified: 19 September 2026.