Siding Calculator

Estimate siding coverage for multiple exterior walls, subtract openings and allow for waste and package sizes.

Estimated Result

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Review inputs and totals

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How to Use the Siding Calculator

Enter each rectangular wall’s width and height in feet. Add rows for additional walls. Add window and door opening widths and heights in feet, counting each opening once. Choose the waste percentage and optionally enter the manufacturer’s installed coverage per package in square feet. Calculate to review gross area, deductions, net area and the purchase-area estimate.

Formula and Explanation

Net area = Σ(wall width × height) − Σ(opening width × height)
Coverage area = net area × (1 + waste ÷ 100)
Packages = ceil(coverage area ÷ package coverage)

Gross wall area = sum of width × height for all walls. Opening area = sum of opening width × height. Net area = gross minus openings. Estimated siding area = net area × (1 + waste percentage ÷ 100). If package coverage is entered, packages = ceiling(estimated siding area ÷ coverage per package).

This model uses rectangular wall areas and total opening deductions. Actual quantities depend on wall shape, gables, siding profile, overlap, installation method and manufacturer coverage. Triangular gables, trim, corners and accessories need separate consideration. Openings cannot exceed gross wall area. These estimates are not guaranteed purchase quantities.

Worked Example

Walls of 30 × 10 feet and 20 × 10 feet have a gross area of 500 sq ft. Subtract a 3 × 7 foot door and a 4 × 5 foot window: 500 − 21 − 20 = 459 sq ft. With 10% waste, estimate 504.9 sq ft. At 100 sq ft per package, round up to six packages.

Frequently Asked Questions

Should I enter wall dimensions in feet or inches?

Use feet throughout. Convert inches to a fraction of a foot by dividing by 12; for example, 8 feet 6 inches is 8.5 feet. Package coverage must be in square feet.

How are windows and doors deducted?

Enter each opening’s width and height once. Their combined area is subtracted from the sum of all walls. The calculator checks the combined total but does not assign each opening to a particular wall.

Does 10% waste suit every siding project?

No. Ten percent is an editable starting assumption. Cuts, layout, product profile and site conditions may require a different allowance. Follow the manufacturer’s coverage and installation guidance.

Does this include gables, trim or corner pieces?

Not automatically. It estimates rectangular wall coverage only. Measure nonrectangular surfaces separately and plan trim, corner pieces and other accessories according to the siding system.