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Roofing Material & Shingle Calculator

Flat (0/12) Low Slope (2/12) 4/12 Pitch 6/12 Pitch 8/12 Pitch 10/12 Pitch 12/12 Pitch

10% (Standard) 15% (Complex Gable) 20% (Hip / High Detail)

Estimation Results:

Total Roof Area: 0 sq. ft.

Roofing Squares: 0 (100 sq. ft. units)

Bundles Needed: 0 (3 bundles per square)

*Includes selected waste factor and standard 3-tab shingle coverage.

function calculateRoofing() { var length = parseFloat(document.getElementById('roofLength').value); var width = parseFloat(document.getElementById('roofWidth').value); var pitchMultiplier = parseFloat(document.getElementById('roofPitch').value); var waste = parseFloat(document.getElementById('wasteFactor').value); if (isNaN(length) || isNaN(width) || length <= 0 || width <= 0) { alert("Please enter valid positive numbers for length and width."); return; } var baseArea = length * width; var actualSurfaceArea = baseArea * pitchMultiplier; var totalWithWaste = actualSurfaceArea * waste; var squares = totalWithWaste / 100; var bundles = Math.ceil(squares * 3); document.getElementById('resTotalArea').innerHTML = Math.round(totalWithWaste).toLocaleString(); document.getElementById('resSquares').innerHTML = squares.toFixed(2); document.getElementById('resBundles').innerHTML = bundles; document.getElementById('roofResult').style.display = 'block'; }

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How to Calculate Roofing Materials

Estimating roofing materials accurately is the difference between a successful project and a logistics nightmare. This calculator helps you determine the total surface area of your roof, the number of roofing "squares" you need, and the total bundles of shingles to order.

Understanding the "Square" in Roofing

In the roofing industry, a "square" is a unit of measurement equal to 100 square feet. Most asphalt shingles are sold in bundles, where three bundles typically cover one square of roof area. If your calculator shows you need 15.5 squares, you are actually covering 1,550 square feet.

The Impact of Roof Pitch

You cannot simply measure the footprint (length x width) of your house to find the roof area unless the roof is perfectly flat. As the pitch (steepness) increases, the surface area increases. For example:

• 4/12 Pitch: For every 12 inches of horizontal run, the roof rises 4 inches. This adds about 3% more surface area than a flat roof.
• 12/12 Pitch: This 45-degree angle adds approximately 41% more surface area compared to the flat footprint.

Factoring in Waste

No roofing project uses 100% of the material perfectly. Shingles must be cut at valleys, hips, and rakes. Professional roofers recommend these waste factors:

• 10%: Standard gable roofs with few penetrations.
• 15%: Complex gable roofs with dormers or skylights.
• 20%: Hip roofs, which require significantly more cutting and overlapping at the ridges.

Example Calculation

Imagine a house that is 40 feet long and 30 feet wide with a 6/12 pitch:

1. Base Area: 40 x 30 = 1,200 sq. ft.
2. Pitch Multiplier: 6/12 pitch has a multiplier of 1.083.
3. Actual Surface: 1,200 x 1.083 = 1,299.6 sq. ft.
4. Waste (10%): 1,299.6 x 1.10 = 1,429.56 sq. ft.
5. Squares: 1,429.56 / 100 = 14.30 squares.
6. Bundles: 14.30 x 3 = 43 bundles (rounded up).