Siding Calculator

Enter your wall dimensions and openings and get siding squares to order — doors and windows deducted and a waste allowance added, with a metric equivalent.

Inputs
ft ×
ft
ft
Doors2
Windows6
Results update as you type — no submit
ResultsLIVE
Siding squares
14 squares
for ≈ 1,268 sq ft net wall (117.8 m²)
Net wall area1,268 sq ft (117.8 m²)
Gross wall area1,400 sq ft
Openings deducted132 sq ft
Formula
net = 1,400 − 132 = 1,268 sq ft
squares = ceil(1,268 ÷ 100 × 1.1) = 14
One siding square = 100 sq ft. Doors ≈ 21 sq ft and windows ≈ 15 sq ft are deducted. Add gable triangles separately; trim and corners are priced by the linear foot.
Diagram — wall elevationNTS
40 ft10 ftNET 1,268 SQ FTWALL ELEVATION · PERIMETER × HEIGHT
MeasureShedmeasureshed.com/calculator/siding-calculator
Siding — material listUNITS: FT · SCALE: NTS
Inputs
Footprint40 ft × 30 ft
Wall height10 ft
Doors / windows2 / 6
Waste+10%
Results
Siding squares14 squares
Net wall area1,268 sq ft
Openings deducted132 sq ft
Diagram — wall elevationNTS
40 ft10 ftNET 1,268 SQ FTWALL ELEVATION · PERIMETER × HEIGHT
Shopping list
☐ 14 squares siding (field only)
Formula
net = 1,400 − 132 = 1,268 sq ft
squares = ceil(1,268 ÷ 100 × 1.1) = 14
Estimates for planning only — verify before purchaseSHEET 1 OF 1
How it works

Siding is estimated by the square — `100` square feet of wall — the same unit roofers use. To find how many squares your house needs, start with the gross wall area, subtract the openings, and divide by `100`.

The gross wall area is the perimeter of the house times the wall height. For a rectangular footprint the perimeter is twice the length plus twice the width, so a `40` by `30` foot house has a `140`-foot perimeter; at `10` feet tall that is `1,400` square feet of wall before any deductions. Then you subtract the doors and windows, because you do not side over them. A standard entry door is about `21` square feet and an average window about `15`, so a couple of doors and a handful of windows can knock off a hundred square feet or more.

What is left is the net wall area. Divide by `100` for squares, then add a waste allowance — `10` percent is typical, more for lap siding with a lot of corners and short runs where off-cuts pile up. The calculator rounds the result up so you order whole squares. Trim, corner posts, and starter strip are separate items priced by the linear foot; this tool sizes the field siding itself.

If your walls include gable triangles above the eave line, add their area separately — a gable adds half the base times the height of the triangle. For a first pass, the perimeter-times-height method gets you close.

Worked example
House `40 ft` × `30 ft` · wall height `10 ft` · `2` doors · `6` windows · `+10%` waste
gross wall = `140 ft` perimeter × `10 ft` = `1,400 sq ft`
openings = `2 × 21` + `6 × 15` = `132 sq ft`
net wall = `1,400 − 132` = `1,268 sq ft`
squares = `1,268 ÷ 100 × 1.10` = `13.9` → round up to `14` squares
Questions from the wall
100 square feet of wall coverage. Vinyl, fiber-cement, and wood lap siding are all estimated and often sold by the square, so converting your wall area into squares lets you order in the supplier's units.
SOURCES — Vinyl Siding Institute estimating guidance · James Hardie estimating sheets · square = 100 sq ft
Estimates for planning only — verify before purchase
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