How to Calculate Siding

Siding Estimation Calculator

Calculation Summary

Net Wall Area: 0 sq. ft.

Area with Waste: 0 sq. ft.

Squares Needed: 0

Estimated Cost: $0

*1 Square = 100 square feet of siding.

function calculateSiding() { var length = parseFloat(document.getElementById('wallLength').value) || 0; var height = parseFloat(document.getElementById('wallHeight').value) || 0; var doors = parseFloat(document.getElementById('doorCount').value) || 0; var windows = parseFloat(document.getElementById('windowCount').value) || 0; var waste = parseFloat(document.getElementById('wasteFactor').value) || 0; var cost = parseFloat(document.getElementById('costPerSquare').value) || 0; if (length <= 0 || height <= 0) { alert("Please enter valid dimensions for wall length and height."); return; } var totalWallArea = length * height; // Subtracting average sizes: Door ~21sqft, Window ~12sqft var deductionArea = (doors * 21) + (windows * 12); var netArea = totalWallArea – deductionArea; if (netArea 0) { document.getElementById('resCost').innerText = totalCost.toLocaleString(undefined, {minimumFractionDigits: 2, maximumFractionDigits: 2}); document.getElementById('costDisplay').style.display = 'block'; } else { document.getElementById('costDisplay').style.display = 'none'; } document.getElementById('siding-results').style.display = 'block'; }

How to Calculate Siding for Your Home

Estimating siding is a crucial first step for any home renovation project. Whether you are installing vinyl, fiber cement (Hardie board), or wood siding, knowing exactly how much material to order prevents costly mid-project trips to the hardware store and minimizes expensive waste.

1. Measure the Exterior Walls

The most accurate way to calculate siding is to measure each wall of your home individually. Start by measuring the width and height of every rectangular section. Multiply the width by the height to get the gross square footage of that wall.

• Rectangular Walls: Length × Height = Square Footage
• Gable Ends (Triangles): (Base × Height) ÷ 2 = Square Footage

2. Subtract Openings (Windows and Doors)

You don't want to pay for siding that will be cut out for windows and doors. On average, a standard exterior door is approximately 21 square feet, and a standard window is roughly 12 to 15 square feet. Calculate the total area of these openings and subtract them from your gross wall area to find your "Net Area."

3. Understanding "Squares"

In the siding industry, materials are almost always sold by the Square. One square is equal to 100 square feet of coverage. If your home requires 2,250 square feet of siding, you would need to purchase 22.5 squares.

4. Accounting for Waste

No project is perfectly efficient. You will have to cut pieces to fit around corners, soffits, and gables, leading to scrap material. A standard rule of thumb is to add a 10% waste factor. For more complex homes with many angles and gables, you might increase this to 15% or 20%.

Example Calculation

Imagine a simple rectangular garage with a total perimeter of 100 feet and a height of 10 feet:

• Gross Wall Area: 100 ft × 10 ft = 1,000 sq. ft.
• Subtract Openings: 1 Door (21 sq. ft.) + 2 Windows (24 sq. ft.) = 45 sq. ft. deduction.
• Net Area: 1,000 – 45 = 955 sq. ft.
• With 10% Waste: 955 × 1.10 = 1,050.5 sq. ft.
• Squares to Order: 1,050.5 ÷ 100 = 10.5 Squares.

Pro Tips for Siding Estimation

When using this siding calculator, keep these professional tips in mind to ensure your project stays on budget:

• Check the Profile: Different siding profiles (e.g., Dutch Lap vs. Board and Batten) have different exposure rates, but the "Square" coverage remains the same.
• Don't Forget Trim: This calculator estimates the main siding panels. Remember to calculate corner posts, J-channels, starter strips, and fascia separately, as these are sold by the linear foot.
• Bundle for Savings: Most suppliers offer discounts when purchasing full squares rather than individual pieces.