Siding & Cladding Calculator
Net siding area from walls and gables minus openings, with waste, pieces from the coverage of your board or panel, plus trim and corner post lengths.
Wall, gable, opening and net areas, the area with waste, a piece count from the coverage you enter, and linear totals for opening trim and corner posts.
Example: A 40 × 30 ft house, 9 ft walls with one 6 ft gable, six 3 × 4 windows and a door: 1,287 ft² net, 1,416 ft² with 10 % waste, 177 boards at 8 ft² each, 104 ft of opening trim.
Walls plus gables,
minus openings.
How the area is built up, what coverage means, and the linear items.
Area
Each wall is length × height; a gable above it is a triangle, ½ × wall length × rise. Openings you list are subtracted (width × height × count). Waste is added as a percentage — lap siding around openings and gables wastes more than sheet panels on a blank wall, and the product sheet gives a figure.
Pieces
Pieces = ⌈area with waste ÷ net coverage per piece⌉. Net coverage is what one board, panel or pack actually covers after laps: exposure × length for lap boards, the sheet size for panels — from the product, not assumed.
Linear items
Opening trim = the perimeter of every opening; corner posts = count × height; the wall perimeter is shown for starter strip and drip edge. J-channel, flashing and fasteners are not counted. Nothing leaves the browser; the same four anonymous usage counts as the rest of the site apply.
SOURCES
- Plane geometry: wall rectangles, gable triangles, opening rectangles subtracted; pieces from net coverage entered from the product (no coverage assumed)
Last reviewed 20 September 2026. How results are checked: How we verify.