Siding Calculator
Estimate vinyl or fiber-cement siding square footage and squares from wall dimensions, doors, windows, and waste. Optional price per sq ft.
How to use this siding calculator
Siding is ordered from net wall area after openings, plus waste for cuts around windows. Vinyl, fiber cement, and engineered wood all start from square feet; some manufacturers also talk in squares (100 sq ft), the same unit roofers use. Gables are extra triangles — add another “wall” with average height or split into a rectangle plus a triangle using the Square Footage Calculator.
This siding calculator uses 20 sq ft per door and 15 sq ft per window. Picture windows and sliders are larger — bump the window count or add leftover area into length. Starter strip, J-channel, and corners are linear-foot accessories, not in the square-foot total.
Formula
Worked example
Four 40×10 ft walls, two doors, eight windows, 10% waste: 1,600 − 40 − 120 = 1,440 net × 1.10 = 1,584 sq ft ≈ 15.8 squares.
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Frequently asked questions
How do I calculate siding square footage?
Add up wall length × height, subtract doors and windows, then add 10% waste.
What is a square of siding?
100 sq ft, same as a roofing square.
Do gables count?
Yes. Treat each gable as extra area (base × height ÷ 2) or as another wall with an average height.
Vinyl vs fiber-cement waste?
Fiber cement often wants a bit more waste because you cannot bend offcuts the same way. 10–12% is a reasonable start.
Is housewrap included?
No. Housewrap is its own roll coverage, usually the gross wall area plus overlap.
Results are estimates for informational purposes and are not financial, legal, or professional advice. Last reviewed 2026-08-19.