Siding Calculator
Free siding calculator. Enter your house dimensions, wall height, gable height, and door and window count to get squares of siding needed and estimated cost.
House Dimensions
Floor to soffit / eave height
Peak height above the eave
Doors & Windows
Deducts 20 sq ft each
Deducts 15 sq ft each
Cost Estimation (Optional)
Vinyl lap ~$100–$180/sq, fiber cement ~$150–$250/sq
Enter your house dimensions to see results.
About this calculator
How to Calculate Siding for a House
Exterior siding is sold in squares — one square equals 100 square feet of coverage. Getting the count right before you order saves money, prevents job-site delays from running short, and avoids the waste of over-buying material that sits in a garage for a decade. The math is straightforward once you know the steps, and this calculator handles every step automatically.
The Core Formula
Net area = Gross area − (Doors × 20 sq ft) − (Windows × 15 sq ft)
Squares = Ceiling( Net area × (1 + Waste%) / 100 )
Perimeter is 2 × (length + width). Gable area for a symmetric gabled roof is width × gable height (which equals the combined area of both triangular gable ends). Always use ceiling division so you buy whole squares, never partial ones.
Worked Example: A 40 × 30 Ranch House
Take a one-story ranch home, 40 ft × 30 ft, 9-foot walls, a 5-foot gable on each end, two exterior doors, and eight windows.
- Perimeter: 2 × (40 + 30) = 140 ft
- Wall area: 140 × 9 = 1,260 sq ft
- Gable area: 30 × 5 = 150 sq ft (both gable ends combined)
- Gross area: 1,260 + 150 = 1,410 sq ft
- Openings: 2 × 20 + 8 × 15 = 40 + 120 = 160 sq ft
- Net area: 1,410 − 160 = 1,250 sq ft
- With 10% waste: 1,250 × 1.10 = 1,375 sq ft = 13.75 squares → order 14 squares
Siding Types Compared
All siding types use the same area formula, but coverage, price, installation method, and durability vary considerably. Choose your material before you order — the calculator stays accurate regardless of which product you pick.
| Type | Unit | Typical Cost (material) | Lifespan |
|---|---|---|---|
| Vinyl Lap | Square | $50–$120/sq | 30–40 years |
| Wood Clapboard | Square | $80–$200/sq | 20–40 years |
| Fiber Cement (HardiePlank) | Square | $80–$150/sq | 50+ years |
| T1-11 Plywood | 4×8 sheet | $28–$60/sheet | 10–20 years |
| Board & Batten | 4×8 sheet | $35–$80/sheet | 15–30 years |
Prices are material-only estimates and vary by region. Add installation labor of $1.50–$4.00 per square foot depending on the product and local market.
Vinyl Lap Siding
Vinyl is the most popular siding type in the United States, accounting for more than a third of all new residential installations. It is sold in boxes covering a set number of squares. A standard box of double-4 vinyl covers two squares (200 sq ft); check the label on your chosen product. The material itself is virtually maintenance-free — no painting, no caulking joints, and it does not rot or rust. The main weaknesses are brittleness in extreme cold (below −20°F) and a hollow sound when struck, which some homeowners find aesthetically inferior to wood or fiber cement.
For a DIY installation, vinyl is the most forgiving. The planks lock together with a simple snap-and-nail system, and most homeowners with basic carpentry skills can install 3–5 squares per day working alone. That makes it the best choice for budget-conscious projects where labor costs would otherwise dominate the total.
Fiber Cement Siding
HardiePlank and similar fiber cement products offer the best balance of durability, aesthetics, and fire resistance. Fiber cement is made from sand, cement, and cellulose fibers, making it impervious to rot, pests, and moisture. It is Class A fire-rated, which can lower homeowner insurance premiums in fire-prone areas. The material holds paint exceptionally well and arrives pre-primed for topcoating.
The downside is weight — fiber cement is roughly eight times heavier than vinyl, which means heavier trim, more careful handling, and specialized cutting tools (fiber cement shears or a carbide-tipped saw blade). Installation labor is substantially higher than vinyl, typically $1.50–$3.50 per square foot versus $0.75–$2.00 for vinyl. Plan for a two-person crew on any project larger than a small shed.
T1-11 and Sheet Panel Siding
T1-11 is a plywood or OSB panel with vertical grooves routed to mimic board-and-batten siding. Each panel is 4 feet wide by 8 feet tall (32 sq ft), which makes calculating sheets straightforward: divide your net area by 32 and round up. T1-11 is popular on outbuildings, garages, barns, and cabins because it goes up fast — a single panel covers a large area, and the tongue-and-groove edge detail seals joints without trim.
The main vulnerability is moisture infiltration at the bottom edge and at horizontal joints when panels are stacked on two-story walls. Factory-treated OSB panels (LP SmartSide or similar) significantly outperform unfaced T1-11 in wet climates and come with a 50-year warranty. If you choose unfaced T1-11, prime all six faces and install a continuous 6-mil poly barrier behind the panels.
Waste Factors by Project Type
The right waste factor prevents both costly shortages and excessive overage. These guidelines are based on contractor field experience and manufacturer installation guides.
| Project Type | Waste Factor | Reason |
|---|---|---|
| Simple ranch, few corners | 10% | Minimal cuts, straight runs |
| Two-story with dormers | 15% | More angles, more offcuts |
| Complex hips and valleys | 15–20% | Many mitered returns |
| Diagonal installation | 20% | Every course is an angled cut |
| Board & batten | 15% | Vertical seams, batten overlap |
Understanding "Squares" vs. Linear Feet vs. Pieces
Siding is sometimes priced per linear foot (especially solid wood), per panel (for T1-11 or sheet goods), or per square. The square is the universal coverage unit because it is independent of plank width, making it easy to compare products and verify contractor quotes. Here is how to convert between them.
- Squares to sq ft: Multiply by 100. 14 squares = 1,400 sq ft.
- Sq ft to T1-11 sheets: Divide by 32 (a 4×8 sheet) and round up. 1,400 sq ft ÷ 32 = 43.75 → 44 sheets.
- Linear feet of lap siding: Divide sq ft by the exposure width in feet. For 5-inch (0.417 ft) exposure: 1,400 ÷ 0.417 = 3,357 linear feet.
- Boxes of vinyl: One box typically covers 2 squares; check the label. 14 squares ÷ 2 = 7 boxes.
Siding Installation Tips
- Start with house wrap: Install a continuous weather-resistant barrier (Tyvek, Typar, or 30-lb felt) behind all siding types. This is your moisture line — siding is the cladding, not the waterproofing.
- Nail into studs, not just sheathing: Siding fasteners must hit studs (16 or 24 inches on center) to resist wind uplift. Mark stud locations with chalk line before hanging the first course.
- Leave expansion gaps for vinyl: Vinyl expands and contracts significantly with temperature. Follow the manufacturer's recommendation for expansion gaps at all butt joints, corners, and trim (usually 1/8 to 3/16 inch).
- Buy from one production run: Color variation between production runs is a known issue with all siding types. Purchase your full order at once to keep consistent color across the entire project.
- Keep a repair kit: Order one extra square (or two extra sheets for T1-11). Future storm damage, impact damage, or woodpecker attacks are hard to match if the product line is discontinued.
Whether you are replacing worn vinyl on a suburban ranch or wrapping a new barn in T1-11, the material math is the same: measure the wall faces, account for the gables, subtract openings, add a waste buffer, and divide by 100 for squares. Enter your dimensions above and the calculator handles everything from area to cost estimate in seconds.
Questions
How do I calculate how many squares of siding I need?+
What is a "square" of siding?+
How much waste should I add for siding?+
Do I subtract doors and windows from the siding area?+
How do I measure the gable area?+
How many sheets of T1-11 do I need?+
What is the difference between vinyl lap siding and fiber cement?+
Can I use this calculator for a non-rectangular house?+
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This calculator provides rough estimates for planning purposes only. Default values are based on general industry reference data. Actual quantities may vary. Always verify with a licensed professional before purchasing materials or beginning construction. Full disclaimer.