How to Calculate Siding Square Footage

Siding Square Footage Calculator

Estimate the exact amount of siding material needed for your project.

Gables (Triangular Sections)

Standard door: 20 sq ft | Window: 15 sq ft

5% (Simple Design) 10% (Standard) 15% (Complex Design) 20% (Very Complex)

Calculation Results:

Net Wall Area: 0 sq ft

Gable Area: 0 sq ft

Total with Waste: 0 sq ft

Siding Squares: 0 Squares

* 1 Square = 100 Square Feet.

function calculateSiding() { var perimeter = parseFloat(document.getElementById('perimeter').value) || 0; var wallHeight = parseFloat(document.getElementById('wallHeight').value) || 0; var gableBase = parseFloat(document.getElementById('gableBase').value) || 0; var gableHeight = parseFloat(document.getElementById('gableHeight').value) || 0; var gableCount = parseFloat(document.getElementById('gableCount').value) || 0; var deductions = parseFloat(document.getElementById('deductions').value) || 0; var wastePercent = parseFloat(document.getElementById('wasteFactor').value) || 10; var wallArea = perimeter * wallHeight; var totalGableArea = (0.5 * gableBase * gableHeight) * gableCount; var subtotal = (wallArea + totalGableArea) – deductions; if (subtotal < 0) subtotal = 0; var totalWithWaste = subtotal * (1 + (wastePercent / 100)); var squares = totalWithWaste / 100; document.getElementById('netArea').innerText = wallArea.toFixed(2); document.getElementById('totalGableArea').innerText = totalGableArea.toFixed(2); document.getElementById('finalTotal').innerText = totalWithWaste.toFixed(2); document.getElementById('sidingSquares').innerText = squares.toFixed(2); document.getElementById('resultArea').style.display = 'block'; }

How to Calculate Siding Square Footage

Accurately measuring your home for new siding is the most critical step in budgeting and planning your exterior renovation. Ordering too much material leads to wasted money, while ordering too little can cause project delays and color-match issues with different batches.

The Basic Siding Formula

The standard formula for calculating siding is:

(Total Wall Area + Gable Area – Window/Door Area) x Waste Factor = Total Siding Needed

Step-by-Step Instructions

1. Measure the Perimeter: Walk around your house and measure the length of every wall. Add these together to get the total perimeter.
2. Measure Wall Height: Measure from the bottom of the existing siding (where it meets the foundation) to the eave (top of the wall). If heights vary, calculate sections separately.
3. Calculate Gables: For triangular sections, measure the base width and the height from the base to the peak. Use the triangle area formula: (Base x Height) / 2.
4. Deduct Openings: Calculate the area of all doors and windows. A standard door is roughly 20 sq ft, and an average window is 15 sq ft. Subtract this total from your wall area.
5. Convert to Squares: In the siding industry, materials are sold by the "Square." One square equals 100 square feet.

Understanding the Waste Factor

No siding project uses 100% of the material. You must account for cuts, overlaps, and mistakes. We recommend the following waste percentages:

• 5-10%: Simple rectangular homes with few windows.
• 15%: Homes with multiple stories, complex gables, or many windows.
• 20%+: High-complexity designs with turrets, dormers, or non-standard angles.

Example Calculation

Suppose you have a rectangular house with a 100 ft perimeter and 10 ft walls. You have two gables with a 20 ft base and 8 ft height, and you have 150 sq ft of windows/doors.

• Wall Area: 100 ft x 10 ft = 1,000 sq ft
• Gable Area: (20 ft x 8 ft / 2) x 2 gables = 160 sq ft
• Subtotal: 1,160 sq ft – 150 sq ft = 1,010 sq ft
• Total with 10% Waste: 1,010 x 1.10 = 1,111 sq ft
• Result: 11.11 Squares of siding.