By Zencalcy Editorial TeamLast reviewed About us
Siding is sold by the square, which is 100 square feet. Measure the wall area, deduct large openings, add 10% for cuts at gables and corners, then divide by 100. Trim, corners and soffit are separate line items.
Squares of siding for a house exterior.
Area = L × W Units = ⌈Area × (1 + waste) ÷ coverage⌉ Cost = Units × price
One square covers 100 sq ft per square. Units are rounded up because suppliers sell whole squares, and the waste allowance covers cuts, mistakes and future repairs.
| Symbol | Meaning |
|---|---|
| L, W | Room length and width (or wall length and height). |
| A | Area to cover, in square feet. |
| w | Waste allowance as a percentage. |
| N | Number of squares to buy, rounded up. |
1,440 sq ft plus 10% is 1,584 sq ft, or 16 squares. Gable ends add roughly 200 sq ft more.
Continue with the Paint Calculator, Wallpaper Calculator, Tile Calculator, or the Flooring Calculator — or browse more home & garden projects and all construction calculators.
100 sq ft of finished wall area.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
Last reviewed: September 2026. See how we build and check every tool on the about page.
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Content updated: September 2026