Siding Calculator
Walls by perimeter × height, gables as triangles, openings subtracted — the tool reports siding squares (100 sq ft each, the industry's ordering definition) and, if you enter your profile's exposure and piece length, whole pieces to buy. Coverage per piece always comes from your product's spec, because profiles vary too much for built-in numbers.
Walls, gables, openings
Example: 150 ft perimeter × 8 ft walls + two 24 × 6 ft gables − 120 sq ft of openings at 10% waste → 13.46 squares, 270 pieces of a 5 in × 12 ft profile.
Quantities only: fastening schedules, water-resistive barriers, clearances, and wind ratings are installation and code matters — follow the manufacturer's instructions and your local requirements.
Area first, squares by definition, pieces from your spec
The worked house: 150 ft of perimeter × 8 ft = 1,200 sq ft of wall, plus two gables at ½ × 24 × 6 = 144 sq ft together, minus 120 sq ft of openings = 1,224 sq ft — 12.24 squares, since a square is 100 sq ft by the industry's ordering definition. With 10% cutting waste that is 13.46 squares; at the example profile's 5 sq ft per piece (5 in exposure × 12 ft), 270 pieces. Computed at build time by the same engine wired to the form.
What is sourced, what is yours
One citation and one convention: the 100 sq ft square is the Vinyl Siding Institute's stated ordering definition, and the 10% waste default is the common cutting convention, labeled and adjustable. Everything that varies by product — exposure, piece length, price — is user-entered, and the openings treatment is explicit where the trade's worksheet keeps it implicit.
The rest of the exterior
Measuring the wall area a different way? The square footage calculator adds arbitrary rectangles, and painted exteriors size their coats with the paint calculator from the same perimeter-×-height area. Roof squares — the same 100 sq ft convention pitched upward — live in the roofing shingle calculator, and trim runs in the linear feet calculator.
Frequently asked questions
What is a "square" of siding?
100 square feet of wall — the trade's ordering definition, stated verbatim in the Vinyl Siding Institute's installation manual: "Every 100 square feet (9.29 square meters) is called a 'square' for ordering purposes." It is the same convention roofing uses, and it is a definition rather than a measurement, so the squares figure here is exact arithmetic on your wall area.
Why do I have to enter the piece exposure and length myself?
Because profiles genuinely differ: a "double 4" vinyl panel exposes 8 inches over 12 or 12.5 feet, a double 5 exposes 10, fiber-cement lap boards expose anywhere from 4 to 8.5 inches depending on the board and the overlap you install. Any built-in figure would silently mis-count somebody’s product, so the coverage per piece — exposure ÷ 12 × length — always comes from your product’s spec sheet. The placeholders are examples, not defaults.
Should I subtract windows and doors?
This tool subtracts what you enter, and its waste margin is explicit. Note the trade often does it the other way: the VSI estimating worksheet leaves normal windows and doors IN the area as an implicit waste allowance, deducting only very large openings like garage doors. Either method lands close — just do not do both (skip the deduction and add full waste) or neither.
How are gables measured?
As triangles: half of the gable base times its height, per gable — the same formula the VSI worksheet uses. Enter the base (usually the house width) and the height from the eave line to the peak, and the count if you have several matching gables.
Does the tool cover trim, starter strip, and channels?
No — deliberately. J-channel, starter, corner posts, and utility trim are linear-foot items that depend on your opening and corner count; measure them with the linear feet calculator rather than a per-square guess.
Dimensions never leave your browser. Sources and the estimating pipeline are documented on the methodology page.