Siding Calculator: Wall Area, Packs & Cost

Estimate siding for up to four rectangular walls or triangular gables. Deduct openings from each section and use the manufacturer's installed coverage per board, panel, pack, or carton to calculate whole purchase units.

Siding area, purchase units, and material cost

Measurement units

Section 1

Section shapeWidth (ft)Height (ft)Openings area (sq ft)

Section 2 (optional)

Section shapeWidth (ft)Height (ft)Openings area (sq ft)

Section 3 (optional)

Section shapeWidth (ft)Height (ft)Openings area (sq ft)

Section 4 (optional)

Section shapeWidth (ft)Height (ft)Openings area (sq ft)

For a triangle, height is the perpendicular rise from its base to the peak, not the sloping edge. Area = width x height / 2. For rectangles, area = width x height. Do not count a gable twice when combining it with the wall beneath it. Openings are deducted only from their own section. Leave all numeric fields in unused sections blank.

Manufacturer installed coverage per purchase unit (sq ft)Extra material allowance (%)Price per purchase unit ($, optional)

Use installed coverage after the specified overlap or exposure, not nominal board or panel area. Match coverage and price to the same purchase unit: one board, panel, pack, or carton. All sections must use the same product and applicable coverage. Run separate estimates for different products. This is not a cutting plan; corners, short runs, and layout constraints may change ordering needs.

Allowance starts at 0% and accepts 0-50%; choose it for your project. Enter dimensions with up to 2 decimal places; openings and coverage accept up to 4. Changing units clears dimensions, openings, and coverage. Prices remain USD.

Enable JavaScript to calculate. Add rectangular areas (width x height) and triangular areas (width x height / 2), subtract their openings, add your chosen allowance, divide by manufacturer installed coverage per purchase unit, and round up.

How do I calculate square footage for siding?

Net siding area = total rectangular wall area + total triangular gable area - openings. Adjusted area = net area x (1 + allowance / 100). Whole purchase units = round up [adjusted area / manufacturer installed coverage per purchase unit].

Worked example

A rectangular wall 20 ft wide and 8 ft high has 160 sq ft of area. Subtract 20 sq ft of openings to get 140 sq ft. A separate triangular gable 20 ft wide and 4 ft high adds 40 sq ft, giving 180 sq ft net. An illustrative 10% allowance gives 198 sq ft, or 1.98 siding squares. At an illustrative 20 sq ft per pack, round up to 10 packs. At $50 per pack, siding material cost is $500. These figures illustrate arithmetic, not standard product coverage, recommended allowance, or market prices.

Can I use this for vinyl, fiber cement, or lap siding?

Use the manufacturer's installed coverage for the exact product, profile, exposure, orientation, and purchase unit. Lap siding overlap means nominal width is not the exposed width. Coverage differs across vinyl, wood, metal, and fiber-cement products, including branded products such as James Hardie. This calculator is independent and does not imply manufacturer endorsement.

What does the cost include?

Only whole purchase units multiplied by your entered price. Trim, starter strips, corners, fasteners, weather barriers, labor, removal, tax, and delivery are separate unless included in that purchase price. This is not an installed-price quote or a location-based cost estimate.

Does the calculator account for cuts and layout?

It estimates area coverage, not individual courses, board cuts, offcut reuse, required lengths, or fastening design. Multiple sections are pooled using one product's coverage. Confirm the final order, accessories, layout, and installation details with your supplier or installer.

Siding measurement guide

How to calculate square footage for siding

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