Walls and gables
Gross area = walls + Σ(base × height ÷ 2 × quantity)
A gable is modeled as a triangle with a perpendicular height.
Siding formulas
How siding area and packages are calculated.
All dimensions convert to canonical units first. The calculator then adds wall and gable areas, handles openings, and applies the selected allowance.
Net siding area
Net area = gross area − selected openings
Opening rows affect the estimate only when subtraction is selected.
Order area
Order area = net area × (1 + allowance %)
The editable allowance starts at 10% and is never changed automatically.
Siding squares and packages
Squares = order ft² ÷ 100; packages = ceil(order area ÷ package coverage)
Squares stay decimal; only whole manufacturer packages are rounded up.
Measure the exterior
Use verified dimensions and product coverage.
Wall square footage
Multiply width by height for each rectangular wall. Use quantities for repeated identical walls.
Gable triangles
Measure the base and perpendicular height, then use half of their product. Divide gambrels, dormers and complex ends into simpler shapes.
Windows and doors
Ordinary openings are included by default because their area can help cover cuts and offcuts. Subtract larger openings when appropriate.
A siding square
A siding square is the North American ordering term for 100 ft². It is a commercial count derived from area, not a new physical unit.
Package coverage
Horizontal profiles, vertical siding, shakes and fiber cement can expose and package material differently. Use the exact manufacturer coverage.
Accessories
Soffit, fascia, trim, starter strips, channels, wrap, insulation and fasteners are not included.
Before you order
What this siding estimate includes
- Walls and openings are modeled as non-overlapping rectangles; gables are modeled as triangles.
- Ordinary doors and windows remain included unless opening subtraction is selected.
- The 10% allowance is editable and never changes automatically for material, orientation, roof pitch or building type.
- Package estimates use only the manufacturer coverage entered for the selected product.
- Siding squares remain decimal and are not rounded to a supplier increment.
- Cost, labor, panels, trim, soffit, fascia, wrap, insulation and fasteners are not included.
Siding squares and openings
Vinyl Siding Institute guidance uses a square as 100 ft² of siding and explains that ordinary doors and windows generally remain in an estimate while unusually large openings may be deducted.
Product coverage and installer or manufacturer guidance remain the source of truth. No carton coverage or panel count is prefilled.
Primary reference
Siding questions
Frequently asked questions
How much siding do I need?
Add the area of walls and gables, optionally subtract appropriate openings, then add an allowance for cuts and fitting. Measivo keeps each step visible.
How many square feet are in a square of siding?
One siding square equals 100 square feet. Metric results can still show this North American ordering term as secondary information.
Should I subtract windows and doors?
Ordinary openings are often left included to help cover cuts and offcuts. Consider subtracting very large openings and follow installer or manufacturer guidance.
How do I calculate siding for a gable?
Multiply the gable base by its perpendicular height and divide by two. Divide more complex roof ends into rectangles and triangles.
How much extra siding should I order?
The calculator starts at 10%, but you can change it. Layout, orientation and product guidance may justify a different planning allowance.
How many cartons of siding do I need?
Enter the exact manufacturer coverage per carton. The calculator divides the order area by that coverage and rounds only the carton count up.
Does this include soffit and trim?
No. Soffit, fascia, trim, starter strips, channels, wrap, fasteners and related accessories require separate estimates.
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Keep planning your project.
Use another Measivo calculator to estimate the next material on your list.