Siding Calculator

Estimate how much siding you need in squares from your exterior wall area minus windows and doors. Add gable ends, choose a siding type and waste factor, and get boxes or panels, total cost and a house elevation diagram.

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Quick examples — click to fill the form, then press Calculate:

📏 Walls

Units

Siding Type

Wall Perimeter

Total distance around the home. Rectangle = 2 × (length + width).

Wall Height

Floor to eaves. Two-story ≈ 18 ft.

🔺 Gable Ends (optional)

Number of Gables

Gable Base Width

Gable Height (rise to peak)

Vertical distance from the top of the wall to the roof peak.

🪟 Openings to Subtract

Doors

~21 sq ft each (3 × 7 ft).

Windows

~12 sq ft each (3 × 4 ft).

Extra Opening Area (optional)

sq ft

Garage doors, bay windows, or any opening not covered above.

⚙️ Waste, Coverage & Cost (optional)

Waste Factor

Auto-set from siding type; adjust for complex homes.

Coverage per Box

sq ft

From the product label; auto-set by type.

Price per Square (optional, for cost)

Material cost per square (100 sq ft). Leave blank to skip cost.

Embed Siding Calculator Widget

About Siding Calculator

The Siding Calculator estimates how much siding you need in squares — the trade unit where 1 square = 100 square feet of coverage. It multiplies your wall perimeter by height, adds any triangular gable ends, subtracts windows and doors, applies a waste factor tuned to your siding type, and converts the result into squares, boxes to order, and an estimated material cost — with an animated house elevation and a visual squares breakdown so the numbers are easy to picture.

What is a "Square" of Siding?

Siding, like roofing, is sold and priced by the square. One square covers 100 square feet of finished wall. So a home with 1,500 square feet of net wall area needs 15 squares of siding before waste. Working in squares makes it easy to compare quotes and order the right number of boxes, because manufacturers list coverage per carton in squares too.

Siding Formula

The calculation is a short chain: gross wall area, minus openings, plus waste, divided by 100.

Step 1 — Gross Wall Area

$$\text{Gross Area} = (\text{Perimeter} \times \text{Height}) + \sum \tfrac{1}{2}\,(\text{base} \times \text{rise})$$

Step 2 — Net Area After Openings

$$\text{Net Area} = \text{Gross Area} - \text{Windows} - \text{Doors}$$

Step 3 — Squares Needed

$$\text{Squares} = \frac{\text{Net Area} \times (1 + \text{Waste}\%)}{100}$$

How Much Waste Should You Add?

Waste covers cut-offs, corners, mistakes, and pattern matching. Use this as a guide, then round up to whole boxes:

Situation	Typical Waste
Simple rectangular home, vinyl or aluminum	10%
Fiber cement or engineered wood lap	12%
Wood clapboard, board & batten, shakes	15%
Many corners, gables, dormers, or angled cuts	15–20%

Siding Types & Coverage

Siding Type	Typical Box Coverage	Notes
Vinyl lap	~200 sq ft (2 squares)	Lightweight, DIY-friendly, low waste
Aluminum	~200 sq ft (2 squares)	Dents easily; keep spares
Fiber cement (HardiePlank)	~100 sq ft (1 square)	Durable but brittle; more cutting waste
Engineered wood (LP SmartSide)	~100 sq ft (1 square)	Long planks reduce end-cut waste
Wood clapboard	~100 sq ft (1 square)	Varies in length; plan for culling
Board & batten / shakes	~100 sq ft (1 square)	More offcuts; higher waste

Coverage per box varies by brand and exposure, so always check the product label — this calculator lets you override the default coverage to match your exact product.

What Affects Your Siding Estimate?

📐 Wall Height & Perimeter

The rectangular wall band — perimeter times height — is usually the biggest slice of the total.

🔺 Gable Ends

Triangular gables under a pitched roof add real area that flat wall math misses.

🪟 Windows & Doors

Large openings reduce the siding needed, but leave the small ones in as free waste allowance.

✂️ Waste & Complexity

Corners, dormers, and pattern-matched courses all increase cut-off waste.

🧱 Siding Material

Product type sets both the typical waste factor and the coverage you get per box.

🎨 Trim & Accessories

Starter strips, J-channel, corner posts, and soffit are ordered separately from field siding.

How to Use This Calculator

Enter wall dimensions: Pick Feet or Meters, then enter the total wall perimeter around your home and the wall height.
Add gables and openings: Enter the number of gable ends with their base and rise, plus how many doors and windows to subtract and any extra opening area.
Choose siding type and waste: Selecting a siding type auto-fills an informed waste factor and coverage per box, which you can adjust.
Calculate: See the squares of siding needed, boxes to order, estimated cost, an elevation diagram, a squares grid, and a full step-by-step breakdown.

Frequently Asked Questions

What is a square of siding?

A square is the standard unit siding is sold and priced in. One square equals 100 square feet of finished wall coverage. If your net wall area is 1,500 square feet, that is 15 squares of siding before waste.

How do I calculate how much siding I need?

Multiply your wall perimeter by the wall height to get the gross wall area, add any triangular gable areas, subtract the area of windows and doors, add a waste factor of about 10 to 15 percent, then divide by 100 to convert to squares.

How much waste should I add for siding?

A waste factor of 10 percent is typical for simple rectangular homes with vinyl or aluminum siding. Add 12 to 15 percent for fiber cement, wood, board and batten, or shakes, and for homes with many corners, gables, or angled cuts.

Do I subtract windows and doors from siding?

Yes. Subtract the area of large openings such as windows and doors from the gross wall area. This calculator uses about 21 square feet per door and 12 square feet per window by default, and you can add any additional opening area.

How do I include gable ends?

A gable is the triangular section of wall beneath a pitched roof. Its area is one half times the base width times the vertical rise. Enter the number of gables plus the base and rise, and the calculator adds that triangular area to your walls.

How many boxes of siding do I need?

Divide your total wall area including waste by the coverage per box, then round up. Vinyl and aluminum cartons typically cover about 200 square feet (2 squares), while fiber cement, engineered wood, and wood lap boxes usually cover about 100 square feet.

Additional Resources

Reference this content, page, or tool as:

"Siding Calculator" at https://MiniWebtool.com/siding-calculator/ from MiniWebtool, https://MiniWebtool.com/

by miniwebtool team. Updated: July 5, 2026