Siding Calculator

How the Siding Calculator Works

Enter your building perimeter, wall height, gable areas, and total window/door area to subtract. The calculator returns net wall area, squares of siding (the industry unit — 1 square = 100 sq ft), trim board linear feet, and nail box counts for the material you select. Waste defaults to 12% because laps, cuts at openings, and starter/course alignment always consume extra material.

Siding Formulas

• Net area = perimeter × height + gables − openings
• Squares = net area ÷ 100 (1 square = 100 sq ft)
• Buy = squares × (1 + waste%), rounded up to whole squares
• Trim: perimeter of every opening + corners and fascia breaks; a 12 ft board yields ~11 usable ft
• Nails: vinyl ≈ 2,000 nails/square using 1½ in roofing nails... actually ~ 2 nails per 12 in of panel coverage — figure one 5,000-count box per 5 squares
• House wrap: 1 roll of 9×100 ft covers 3 squares per layer

Worked Example

A 120 ft perimeter × 9 ft wall with 0 gables and 120 sq ft of openings: net area = 1,080 − 120 = 960 sq ft = 9.6 squares. With 12% waste: order 11 squares. Trim at 150 lin ft = 14 twelve-foot boards. At $350/square, siding costs about $3,850.

Frequently Asked Questions

Why is siding sold in squares? A square covers 100 square feet — the same unit as roofing. A square of vinyl typically weighs 60–100 lb; fiber cement is 2–3× heavier, so expect a lift or helper.

How much siding waste is normal? 10–15% for simple rectangles; up to 20% for houses with many gables, bays, and openings.

How do I calculate gable area? Gable area = ½ × width × height of the triangle. A 24 ft wide gable rising 6 ft adds 72 sq ft per gable end.

Does the calculator include house wrap? House wrap coverage ≈ net wall area ÷ 900 sq ft per 9×100 roll — order one roll per 3 squares with overlap.

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