What Is a Square of Siding? Pieces per Square
One square means 100 sq ft of wall. How many pieces make one depends on the profile, and a carton's “2 squares” is a round number.
A square of siding is 100 square feet of wall, a 10 by 10 ft patch. The installation manual of the Polymeric Exterior Products
Association (formerly the Vinyl Siding Institute) puts it as Every 100 square feet (9.29 square meters) is called a “square” for
ordering purposes.
(VSI manual), and LP as One unit of siding (one square) is equal to 100 square feet
(LP). Divide a wall area by 100 and you have squares. It is not a number of panels, though: how many pieces cover
it depends on how much of each piece shows and how long it is.
Seven profiles, piece by piece
One piece covers its exposure in inches ÷ 12 × its length in feet; 100 ÷ that, rounded up, is the count per square, the way the calculator counts (why round up). The printed column quotes Ply Gem's per-square counts (Ply Gem), which give no panel length.
| Profile | Exposure × length | One piece covers | Pieces per square | Per carton | A carton covers | Printed per-square count |
|---|---|---|---|---|---|---|
| Vinyl double 4" | 8" × 12' 6" | 8.33 sq ft | 12 | 24 Alside | 200.0 sq ft | Double 4″ siding: 12 pieces = 1 square |
| Vinyl double 5" | 10" × 12' | 10 sq ft | 10 | 20 Alside | 200.0 sq ft | Double 5″ siding: 10 pieces = 1 square |
| Vinyl Dutch lap 4-1/2" | 9" × 12' 1" | 9.06 sq ft | 12 | 22 Style Crest | 199.4 sq ft | Double 4-1/2″ siding: 11 pieces = 1 square |
| Steel double 4" | 8" × 12' 6" | 8.33 sq ft | 12 | 12 Alside | 100.0 sq ft | — |
| Fiber cement lap 8-1/4" (7" exposure) | 7" × 12' | 7 sq ft | 15 | — | — | — |
| Engineered wood lap 8" (6-7/8" reveal) | 6.875" × 16' | 9.17 sq ft | 11 | — | — | — |
| Cedar bevel 1x8 (6-1/2" exposed face) | 6.5" × 12' | 6.5 sq ft | 16 | — | — | — |
Two of Ply Gem's three counts match ours at the lengths the catalogs sell. The third, for Ply Gem's double 4-1/2″ profile, does not: Ply Gem prints 11 per square without a panel length; at a 12' 1" panel the round-up gives 12 — check the chart for your product. A per-square count is a shortcut: CladCount divides the whole order area by one piece's coverage and rounds once, which can come out a piece lower than squares times a rounded count.
A carton's squares are nominal
Vinyl cartons carry a square count on the label. Multiply it out panel by panel and it comes close to the label, not always equal. Style Crest
prints Length 12' - 6" | 24 Panels/Ctn. | 2 Sq./Ctn.
and Length 12' - 1" | 22 Panels/Ctn.
with the same two squares
(Style Crest); Alside's 7 in board-and-batten carton holds 17 panels and is listed as one square (Alside).
- 24 × 8 in × 12' 6" = 200.0 sq ft, labelled 2 squares (Style Crest)
- 22 × 9 in × 12' 1" = 199.4 sq ft, labelled 2 squares (Style Crest)
- 17 × 7 in × 10' = 99.2 sq ft, labelled 1 square (Alside)
So a carton of Dutch lap holds a little under its two squares. That is why the calculator counts pieces first and then cartons, rather than dividing squares by the label: for 200 sq ft of the Dutch lap above it needs 23 panels, one more than a carton holds, so two cartons.
From wall area to cartons
A one-story house 40 by 30 ft with 8 ft walls, two gable ends at a 6 in 12 roof pitch, 8 windows of 3 × 5 ft and 2 doors of 3 × 7 ft, vinyl double 4 in, 10 % waste:
- Walls 1,120.0 + gables 225.0 − openings 162.0 = 1,183.0 sq ft net
- 1,183.0 × 1.10 = 1,301.3 sq ft to order = 13.01 squares
- 1,301.3 ÷ 8.33 sq ft per panel → 157 panels
- 157 ÷ 24 per carton → 7 cartons
Squares tell a supplier the size of the job; the panels and cartons are what you carry home. Open in calculator to change any of these measurements.