Exterior Estimating
Vinyl Siding Calculator
Accurately estimate the amount of vinyl siding needed for your project. Enter wall dimensions, account for windows and doors, and calculate square footage for gables to find the total "squares" required.
Vinyl Siding Calculator
Estimate siding order area, squares, and panel count (minus openings) with waste allowance
Tip
Use package specs
Panel length and exposure depend on the profile (D4/D5, etc.). Use the manufacturer spec sheet for best results.
Results
Enter values above to calculate
Calculating Wall & Gable Areas
Siding area equals the wall rectangles plus gable triangles, minus the openings for windows and doors.
Necessary Siding Accessories
Don't forget to estimate the trim and accessories. Siding cannot be installed without these critical components.
| Accessory | Measurement | Purpose |
|---|---|---|
| Starter Strip | Linear Feet/Metres | Secures the first course of siding |
| J-Channel | Linear Feet/Metres | Trims windows, doors, and gables |
| Outside Corners | Vertical Feet/Metres | Protects and trims external wall corners |
| Inside Corners | Vertical Feet/Metres | Trims internal wall corners |
| Undersill Trim | Linear Feet/Metres | Finish trim for top courses and windows |
Step-by-Step Formulas
1. Gross Wall Area
Measure the total area of all exterior walls to be sided. For gables, calculate the triangular area (Base × Height ÷ 2). Sum all areas for a gross total.
2. Subtract Openings
Subtract the area of all windows, doors, and other penetrations. Vinyl siding is sold in "squares" (100 sq ft), so accurate net area prevents over-ordering.
3. Waste Allowance
Add 10% for simple jobs. For complex projects with many gables, corners, or small sections, add 15–20% to account for offcut loss.
4. Convert to Squares
Dividing the total square footage by 100 gives you the number of "squares" to order. Siding, soffit, and underlayment are typically priced and packaged by the square.
Worked Example
One-story house: Four walls (30' × 10'), two gables (30' base × 10' high), 80 sq ft of openings, 10% waste.
Squares, Exposure and Waste
Siding is quoted in squares and installed by exposure, and confusing the two is where most orders go wrong:
- Squares Are the Trade Unit: Siding is sold and priced by the square — 100 square feet of wall coverage. Converting your wall area to squares early makes supplier quotes directly comparable.
- Gables Are Half a Rectangle: A triangular gable end is simply half its width times its height. Forgetting gables is the most common way to under-order on a two-storey elevation.
- Exposure Is Not Panel Width: A panel measuring 12 in wide only exposes about 10 in once lapped over the course below. Estimating on the full panel width undercounts your panels by roughly 20%.
Benefits of Using This Calculator
Example Calculations
Three scenarios worked through step by step:
Example 1 — Single-Storey Walls
Four walls totalling 1,120 ft², 140 ft² openings, 10% waste.
Net area = 1,120 − 140 = 980 ft²
With 10% waste = 980 × 1.10 = 1,078 ft²
Squares = 1,078 ÷ 100 = 10.78
Result: order 11 squares of siding
Example 2 — Gable Ends
Two gables, each 28 ft wide × 7 ft high, 10% waste.
Area per gable = ½ × 28 × 7 = 98 ft²
Two gables = 98 × 2 = 196 ft²
With 10% waste = 196 × 1.10 = 215.6 ft²
Squares = 2.16 → add 2.25 squares to the wall order
Example 3 — Panel Count
1,078 ft² order area, panels 12 ft long with 10 in exposure.
Exposure in feet = 10 ÷ 12 = 0.8333 ft
Coverage per panel = 12 × 0.8333 = 10.0 ft²
Panels = 1,078 ÷ 10.0 = 107.8 → 108 panels
Result: 108 panels (note: exposure, not the 12 in panel width)
Installation Tip
Installation Tip
Never nail vinyl siding tight to the wall. Leave the fastener heads about 1/32 in proud and centre them in the slots so each panel can slide sideways — a 12 ft panel expands and contracts more than half an inch across the seasons. Face-nailed siding buckles in the first hot spell.
Frequently Asked Questions
- What is a siding "square"?
- A "square" is 100 square feet of wall area. Most siding and underlayment materials are sold and priced by the square.
- How much waste should I add for gables?
- Angled gable cuts create more offcut waste. Add 15–20% for gables, compared to 10% for standard walls.
- Can I install vinyl over old siding?
- Yes, if the surface is flat and stable. Use fan-fold insulation as a level underlayment, though removing old siding is better for inspecting the structure.
- How many squares of siding do I need?
- Divide your net wall area (walls plus gables, minus openings) by 100, then add waste. A typical single-storey ranch runs 15–20 squares; a two-storey house often needs 25–35. Suppliers quote per square, so this is the number to ask for.
- What is panel exposure and why does it matter?
- Exposure is the visible height of each course after the panel laps over the one below — usually about 10 in on a nominal 12 in panel, or twice 4, 4.5, or 5 in for double-course profiles. Panel counts must be based on exposure, not overall width.
- How do I calculate a gable end?
- A gable is a triangle, so its area is half the base times the height: ½ × width × rise. For a 28 ft wide gable with a 7 ft rise that is 98 ft². Measure the rise from the top plate to the ridge, not along the rafter.
- How much waste should I allow for siding?
- Ten percent is the usual figure for a straightforward elevation. Increase it to 15% where there are many windows, dormers, or angled cuts at gable rakes, since each cut leaves an offcut that is rarely long enough to start the next course.
- Do I need to subtract windows and doors?
- Deduct the large ones. Small windows are often better left in the gross area, because the siding cut from around them ends up in short unusable pieces. A common compromise is to deduct only openings larger than about 10 ft².
- What trim pieces do I need besides the panels?
- Starter strip along the bottom, J-channel around every window and door, inside and outside corner posts, and utility trim under the soffit. These are ordered by linear foot and are not included in the square count.
- Can I install vinyl siding over existing siding?
- Often yes, provided the existing surface is sound, flat, and you add furring or insulation board to give a consistent nailing plane. Wavy or rotten substrate must be removed first, since vinyl telegraphs every irregularity beneath it.