To estimate siding, add up the exterior wall area, subtract the doors and windows, then divide by the coverage each bundle provides and round up — adding a waste allowance for cuts. Siding is often sold by the "square", which covers 100 square feet. A 1000 sq ft wall with 100 sq ft of openings needs about 10 bundles at 100 sq ft each with 10% waste.
Siding Calculator — how many bundles or squares
Siding for 1,000 sq ft of wall less 100 sq ft of openings.
- Net area to cover (sq ft)
- 900
Quick examples
How it's calculated
- Bundles = (wall − openings) × (1 + waste) ÷ coverage, rounded up
- netArea
- = 900
- 10
How it works
Cladding a house is an area-coverage problem, per Wolfram MathWorld's A = length × width:
- Wall area — measure each wall (length × height) and add them up.
- Openings — subtract the area of doors and windows you are not siding over.
- Bundles = net area ÷ coverage per bundle, times (1 + waste %), rounded up.
Siding is commonly measured in squares, where one square covers 100 square feet; vinyl siding boxes often cover two squares (about 200 ft²). Because coverage varies by product, the calculator takes it as an input. A waste allowance of about 10% covers cutting siding to length around corners, gables and openings — add more for a house with many angles or trim details.
Worked example
For a 1000 ft² wall with 100 ft² of doors and windows, the net area is 900 ft². At 100 ft² per bundle with 10% waste, that is 900 × 1.1 ÷ 100 = 9.9, rounded up to 10 bundles (10 squares of siding).
Frequently asked questions
How much siding do I need?
- Add up the wall area, subtract the doors and windows, then divide by the coverage per bundle and round up. For 900 sq ft of net wall at 100 sq ft per bundle with 10% waste, that is 10 bundles.
What is a "square" of siding?
- A square is a unit of exterior coverage equal to 100 square feet. Siding and roofing are often ordered by the square; one bundle frequently equals one square, and vinyl boxes often cover two.
Do I subtract windows and doors?
- Yes. Subtract the area of large openings you will not side over, so you don't over-order. Small openings are sometimes left in to provide built-in waste for cuts.
How much waste should I allow for siding?
- About 10% is typical, covering cuts around corners, gables, windows and doors. Complex facades with many angles or dormers can need 15% or more.
How do I measure a gable wall?
- A triangular gable's area is half its base times its height (½ × width × peak height). Add that to the rectangular wall below it before subtracting openings.
Does the coverage per bundle change by product?
- Yes. Fiber-cement and wood bundles, vinyl boxes and panels all cover different areas — always read the coverage from the product and enter it, rather than assuming a fixed value.
How we know this is right
- Last reviewed
- Aug 8, 2026
- Precision
- Rounded to 0 decimal places.