Calculate how much siding you need in square feet and squares from house perimeter and wall height, with waste allowance and optional gables and cost.
Siding Formula
Amount and cost modes estimate net wall area and add your chosen waste allowance. Inventory coverage mode instead converts siding already owned to nominal area; it does not add waste or model a cutting layout. These are planning estimates, not a final product takeoff or order recommendation.
Base Area = Perimeter * Height or sum of up to 4 Width * Height areas or entered total wall area Gable Areas = Count * Base * Height / 2 Gross Area = Base Area + Gable Areas
Net Area = Gross Area - Openings
Total Siding = Net Area * (1 + Waste% / 100)
Squares = Total Siding / 100
Panels or Boxes = ceil(Total Siding / Coverage per Unit)
Material cost uses allowance-adjusted area for per-square-foot pricing, fractional squares for per-square pricing, or the rounded-up count for per-panel/box pricing. Installation uses the selected allowance-area billing basis (the default) or net-area basis. Enter prices on the same unit basis:
Material Cost = Total Siding * Price per sq ft or (Total Siding / 100) * Price per square or Panels/Boxes * Price per panel/box Installation Cost = Billing Area * Install Rate Project Cost = Material Cost + Installation Cost
Coverage mode multiplies inventory by the coverage of its selected unit. Enter the actual product coverage for panels or boxes. An optional target gives a nominal area surplus or shortfall; compare on the same basis and include any required cutting allowance in the target:
Area Covered = Amount * Coverage per Unit Area Difference = Area Covered - Target Area
The variables are:
- Perimeter: the distance around the outside of the house at the base of the walls.
- Height: the wall height from the foundation to the eave.
- Gable Areas: the triangular sections under a pitched roof, each equal to one half of base times height.
- Openings: the optional area you choose to deduct under the product or installer's estimating method. Do not assume every window and door should be deducted.
- Waste%: your planning allowance added to net area. It is not a guarantee that every cut, overlap, damage or layout loss is covered.
- Squares: the trade unit for siding, where one square covers 100 square feet.
- Coverage per Panel or Box: the actual exposed coverage stated for the product and unit being counted. Use box coverage for boxes and panel coverage for panels; the required count is rounded up to a whole unit.
Choose siding amount, estimated cost, or coverage of inventory. Wall inputs retain the three measurement methods; optional gables and opening deductions are applied before waste. Named siding types select editable planning waste examples only, not panel coverage. Enter the actual manufacturer coverage when a panel or box count is needed. Display precision does not change the unrounded quantities used for the whole-unit count.
Planning Waste Examples by Siding Type
These percentages are retained calculator examples, not universal product specifications or prescribed allowances. Edit the percentage or choose Custom to match the product instructions, layout and agreed takeoff method. A complex project has no universal 20% maximum.
| Siding Type | Planning Example | Notes |
|---|---|---|
| Horizontal lap / vinyl | 10% | Editable example |
| Dutch lap | 10% | Editable example |
| Vertical / board & batten | 12% | Editable example |
| Shake / shingle | 15% | Editable example |
| Complex layout (any type) | 20% example | User-defined; no universal maximum |
To convert between units, remember that one square always equals 100 square feet.
| Wall Area | Squares |
|---|---|
| 1,000 sq ft | 10 |
| 1,500 sq ft | 15 |
| 2,000 sq ft | 20 |
| 2,500 sq ft | 25 |
Example Problems
Example 1. A 150 ft perimeter and 9 ft wall height give 1,350 sq ft before any gables. For an illustrative takeoff that permits a 120 sq ft deduction, net area is 1,230 sq ft. A user-selected 10% allowance gives 1,353 sq ft, or 13.53 squares. This area calculation does not specify packaging: use the product's actual coverage and round its whole-unit count up.
Example 2. For 2,000 sq ft of net area and an illustrative 15% allowance, estimated siding area is 2,300 sq ft, or 23 squares. At a hypothetical material price of $300 per square, material cost is $6,900. Any entered installation rate uses the selected allowance-area or net-area basis; unentered project items are excluded.
Frequently Asked Questions
What is a square of siding?
A square is an area unit equal to 100 square feet. Divide allowance-adjusted siding area by 100 to obtain squares. Check the product's package quantity and actual exposed coverage before converting that area to panels or boxes.
How much waste should I add?
The 10%, 10%, 12% and 15% named presets are editable planning examples. Use the manufacturer or installer's project-specific method rather than treating a siding style as a guaranteed waste percentage. Custom permits a different allowance; the estimate does not plan individual cuts.
Should I subtract windows and doors?
Not automatically. Follow the product or installer's takeoff method. For example, the Mastic installation guide generally retains window and door area for waste allowance and treats very large openings differently. Optional deductions remain available when appropriate; a fixed waste percentage does not guarantee every trimming loss is covered.
