Siding Calculator
Wall area less openings, then lap siding by the piece from its exposure or panel siding by the sheet, with gables counted as triangles.
Wall area less openings, then lap siding by the piece from its exposure or panel siding by the sheet, with waste and the gables counted as the triangles they are.
| Wall area, gross | — |
|---|---|
| Gables | — |
| Openings deducted | — |
| Net siding area | — |
| With waste | — |
| Lap siding | — |
| Panel siding | — |
Exposure is the number that turns area into pieces. A lap board 8 inches wide shows less than 8 inches; the overlap hides the rest, and the exposure — what actually shows — is what covers the wall. Linear feet = area × 12 ÷ exposure: 969 square feet at an 8-inch exposure is 1,453 linear feet, and at 6 inches it is 1,938. Read the exposure off the product; it is the single figure this page cannot guess.
Gables are triangles, and there are usually two. Half the width times the rise, each. A 28-foot gable rising 7 feet is 98 square feet; two of them are a fifth of a small house’s wall. Left out, the order comes up one wall short and the colour lot may not match when the rest arrives.
Openings come off, corners and trim go on. A door is about 21 square feet, a window about 15; the page deducts them. What it does not add is the corner boards, J-channel, starter strip and trim that a real siding order carries — those are counted by the linear foot of edge, from the same perimeter and heights.
Gross wall = perimeter × eave height; gables = ½ width × rise each; openings at 21 ft² per door and 15 ft² per window (the same nominal sizes the drywall and paint pages use). Lap siding linear feet = net area × 12 ÷ exposure; pieces = linear feet ÷ piece length, rounded up; panels = area ÷ 32 ft², rounded up. Waste is applied before the piece counts.
Worked example
A house with 120 ft of perimeter and 9 ft walls, one door and six windows, in 8-inch-exposure lap siding: how many pieces?
- Gross wall 120 × 9 = 1,080 ft²; less a door (21) and six windows (90): 969 ft².
- With 10% waste, 1,065.9 ft²; at an 8 in exposure that is 1,065.9 × 12 ÷ 8 = 1,599 linear feet.
- In 12 ft pieces: 134. As 4 × 8 panels instead: 34 sheets.
134 twelve-foot pieces. Add two 28 × 7 gables and the net wall becomes 1,165 ft² — the gables are the wall most often left off the order.
13 values on this page were driven in a browser and compared with independently derived figures on 2026-09-05 (418 values across 51 calculators site-wide).
Questions
How much siding do I need for a house?
Perimeter × wall height, plus the gables (½ width × rise each), minus doors and windows, plus about 10% waste. For lap siding, area × 12 ÷ exposure gives the linear feet; 969 ft² at an 8 in exposure is about 1,600 linear feet with waste.
What is siding exposure?
The part of each board that shows once the next one overlaps it. It is smaller than the board width and it is the number that turns area into pieces.