Coverage is measured in squares — 100 sq ft each
Siding is ordered by the square, a unit equal to 100 square feet of wall. Find your net wall area (all walls, minus the openings), divide by 100 for squares, then add waste before you order.
Net wall area is height × length for every wall added together, minus the square footage of windows and doors. A wall 8 ft high and 40 ft long is 320 sq ft, or 3.2 squares before waste.
From squares to boxes
- Squares. Net area ÷ 100. This is the number you compare against product coverage.
- Boxes. A typical vinyl box covers ~200 sq ft, so boxes ≈ squares ÷ 2. Round up to whole boxes; you cannot buy a partial one.
- Waste. Apply 10–15% before rounding. On a 20-square house, 12% waste adds about 2.4 squares — more than a full box.
Quick reference — area to order
| Net wall area | Squares | With 10% waste | Boxes (~200 sq ft) |
|---|---|---|---|
| 1,000 sq ft | 10 | 11.0 | 6 |
| 1,500 sq ft | 15 | 16.5 | 9 |
| 2,000 sq ft | 20 | 22.0 | 11 |
| 2,500 sq ft | 25 | 27.5 | 14 |
| 3,000 sq ft | 30 | 33.0 | 17 |
Box counts are rounded up to whole boxes. Confirm actual coverage on the label — profiles from Dutch lap to board-and-batten cover different areas per box.
What people forget to include
- Gable triangles. The peaked end walls above the eaves are easy to miss; each triangle is ½ × base × height.
- Subtract big openings only. Deduct windows and doors, but leave small gaps in — trimming exactly to every opening leaves you short once cuts are wasted.
- Trim and accessories. Squares cover the field panels only. Starter strip, J-channel, corner posts and soffit are ordered separately by the linear foot.
Common questions
What is a "square" of siding?
A square is 100 square feet of wall coverage — the trade's standard unit for siding, roofing and similar materials. Divide your net wall area by 100 to get the number of squares you need.
How many boxes of vinyl siding are in a square?
Usually two. Most vinyl siding is sold in boxes that cover about 200 square feet, so one box equals roughly two squares. Always check the box label, since panel size varies by profile and brand.
How much waste should I add?
Add 10% for a plain rectangular house and 15% or more if there are many corners, gables, windows or a complex layout. The waste covers cut-offs, mistakes and a few spare panels for future repairs.
