Siding Calculator: Squares, Planks, Gable Ends & Trim Estimator
Use this siding calculator to calculate the exact number of siding squares, individual lap siding planks, and exterior trim accessories required to re-side your home. Accounts for rectangular walls, triangular gable roof ends, window and door deductions, starter strips, and J-channel trim.
Order 18.10 squares (19 full squares / approx 259 planks of 12-ft siding) with 10% waste.
| Rectangular Wall Area | 1,600 sq ft (Openings: -150 sq ft) |
|---|---|
| Gable Triangle Area | 192 sq ft (2 gables @ 24 ft base × 8 ft peak) |
| Net Siding Wall Area | 1,642 sq ft (152.5 sq m) |
| Gross Area with 10% Waste | 1,806 sq ft |
| Total Siding Squares | 18.06 Squares (1 Square = 100 sq ft) |
| Plank Exposure Reveal | 7.0 inches visible face (12-ft board) |
| Individual Siding Boards | 259 planks (12 ft length) |
| Vinyl Siding Cartons (2 sq/box) | 10 boxes |
📐 Show Formula and Default Assumptions
We believe all home improvement estimates should be transparent and verifiable. Below is the exact math running in this browser tool:
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Siding Square Industry Standard:
1 Siding Square = 100 Square Feet of Exterior Wall SurfaceThe universal manufacturing and distributor unit for vinyl, fiber cement, and cedar siding. -
Gable Triangle Area Formula:
Gable Area = Gable Count × (Gable Base × Gable Height ÷ 2)Calculates triangular pitch wall peaks above the standard rectangular wall plates. -
Lap Siding Plank Count Formula:
Planks = ceil( (Total Net Area × (1 + (Waste % ÷ 100))) ÷ Plank Usable Face Area )Usable plank area equals exposed board reveal height multiplied by manufactured board length. -
Trim & Accessory Takeoffs:
Starter Strip = Building Perimeter | J-Channel = Perimeter of Windows + Doors + Rake GablesCalculates essential accessories required to lock panels and finish cut edges cleanly.
Note: All default assumptions (waste %, coverage rates, container yields) can be adjusted directly in the input fields above to match your project specifications.
How to Measure Exterior Walls and Gables for Siding
- Divide home exterior into rectangular wall sections: Measure foundation length and wall height to the eaves for all sides of the house.
- Measure triangular gable roof peaks: Measure horizontal base width along the eave line, and vertical height from eave line up to the peak ridge. Multiply base × height ÷ 2.
- Subtract large door and window openings: Deduct garage doors (approx 120 sq ft for double door), patio doors (approx 40 sq ft), and large picture windows.
- Choose siding reveal / exposure: Standard vinyl siding uses double 4" (8" total exposure) or double 4.5" (9" exposure). Fiber cement (HardiePlank) typically uses 8-1/4" boards with a 7" visible exposure.
- Account for angle cut waste on gables: Rake cuts on steep gables produce significant triangular cut scrap; factor 10% waste for simple walls and 15% for complex gables.
- Measure exterior corner posts: Count all 90-degree outside and inside corners; order 10-foot corner post profiles to run continuous from foundation to soffit.
How the Siding Calculation Works (Worked Example)
Consider siding a two-story home with 1,600 sq ft of rectangular walls, two gable ends (24 ft wide × 8 ft high), 150 sq ft of window/door deductions, and 12-foot lap siding with 7-inch exposure:
- 1. Rectangular Wall Area: 1,600 square feet.
- 2. Gable Peak Area: 2 gables × (24 ft base × 8 ft height ÷ 2) = 2 × 96 sq ft = 192 sq ft.
- 3. Total Gross Area: 1,600 + 192 = 1,792 square feet.
- 4. Subtract Doors and Windows: 1,792 - 150 sq ft = 1,642 square feet net.
- 5. Add 10% Cutting and Rake Waste: 1,642 × 1.10 = 1,806.2 square feet.
- 6. Siding Squares (100 sq ft/square): 1,806.2 ÷ 100 = 18.06 -> Round UP to 19 Squares.
- 7. Individual Planks (12 ft long with 7" exposure = 7.0 sq ft/plank): 1,806.2 ÷ 7.0 = 258 planks (approx 11 to 12 cartons).
- 8. Housewrap Weather Barrier (9 ft × 100 ft rolls = 900 sq ft): 1,806 sq ft requires 2 rolls (with 6" overlap).
Siding Materials, Squares Packaging & Maintenance Life
| Siding Material | Plank Length | Typical Exposure | Carton Packaging | Expected Lifespan |
|---|---|---|---|---|
| Vinyl Siding (Double 4") | 12 ft (3.66 m) | 8.0 inches | 2 Squares / carton (24 pcs) | 30–40 years |
| Vinyl Siding (Double 4.5") | 12 ft (3.66 m) | 9.0 inches | 2 Squares / carton (22 pcs) | 30–40 years |
| Fiber Cement (HardiePlank) | 12 ft (3.66 m) | 7.0 inches | approx 24 pcs / square | 50+ years (fireproof) |
| Engineered Wood (LP SmartSide) | 16 ft (4.88 m) | 7.0 inches | approx 18 pcs / square | 50 years |
| Cedar Lap Siding (Bevel) | 8 to 16 ft | 6.0 inches | Varies by bundle | 30–50 years (stained) |
| Board & Batten Vertical | 10 to 12 ft | 10"–12" board + batten | Sold per panel/board | 40+ years |
Frequently Asked Questions About Siding Calculator
What is a "square" of siding?
A square is the standard construction industry measurement for exterior cladding, representing exactly 100 square feet of surface area. For example, a house with 1,800 square feet of net exterior wall area requires 18 squares of siding.
How do you calculate the area of a gable roof wall peak?
A gable wall is a triangle. The formula is: (Base Width × Vertical Height) ÷ 2. For example, a gable measuring 24 feet wide at the eave and 8 feet tall to the roof peak contains: (24 × 8) ÷ 2 = 96 square feet.
Why must vinyl siding be nailed loosely rather than driven tight?
Vinyl expands and contracts up to 1/2 inch across a 12-foot plank between summer heat and winter freezing. Fasteners must be driven into the center of the nailing slot with a 1/32-inch gap between the nail head and vinyl, allowing the panel to slide freely.
What is the purpose of housewrap under siding?
Housewrap (such as Tyvek) acts as a weather-resistant drainage barrier (WRB). Siding is not 100% waterproof; housewrap prevents wind-driven rain from soaking wood sheathing while allowing interior water vapor to escape outward.
How much cutting waste should I factor into my siding order?
For simple single-story ranch homes with straight walls, 10% waste is standard. For multi-story homes with multiple gables, bay windows, or dormers, order 15% to 20% extra to cover angled rake cuts and short end cutoffs.