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Professional Roofing & Shingle Calculator

Estimate roofing squares, bundles, and surface area based on pitch.

Flat (0/12) 1/12 2/12 3/12 4/12 5/12 6/12 7/12 8/12 9/12 10/12 11/12 12/12

Estimation Results

Ground Area: 0 sq. ft.

Actual Roof Area: 0 sq. ft.

Total Area (inc. waste): 0 sq. ft.

Roofing Squares: 0 sqs.

Bundles Needed: 0

(Based on 3 bundles per square)

How to Estimate Your Roofing Materials

Calculating the amount of shingles for a new roof requires more than just knowing the floor plan of your home. Because roofs are sloped (pitched), the actual surface area of the roof is always larger than the footprint of the building. This calculator helps you determine the "Roofing Squares"—the standard unit of measurement in the industry.

Key Definitions

• Roofing Square: A "square" is a roofing term for 100 square feet of roof area.
• Bundles: Asphalt shingles are typically sold in bundles. It usually takes 3 bundles to cover 1 square of roofing.
• Roof Pitch: This is the steepness of your roof, expressed as a ratio of vertical rise over a 12-inch horizontal run (e.g., 6/12 means the roof rises 6 inches for every 12 inches of horizontal distance).
• Waste Factor: Every roofing project involves cutting shingles to fit valleys, hips, and gables. A standard waste factor is 10-15%.

Example Calculation

Imagine a home that is 40 feet long and 30 feet wide with a 6/12 pitch and a 10% waste factor:

1. Ground Area: 40 ft × 30 ft = 1,200 sq. ft.
2. Pitch Multiplier: A 6/12 pitch has a multiplier of 1.158.
3. Actual Surface Area: 1,200 × 1.158 = 1,389.6 sq. ft.
4. Adding Waste (10%): 1,389.6 × 1.10 = 1,528.56 sq. ft.
5. Result: Approx 15.3 squares, which equals 46 bundles of shingles.

How to Measure Your Roof

To use this calculator effectively, you need the horizontal dimensions of the area the roof covers. This includes any overhangs (eaves). If your roof has multiple sections with different pitches, calculate each section separately and sum the results for the most accurate estimate.

function calculateRoofing() { var length = parseFloat(document.getElementById("roofLength").value); var width = parseFloat(document.getElementById("roofWidth").value); var pitchMultiplier = parseFloat(document.getElementById("roofPitch").value); var wastePercent = 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; } if (isNaN(wastePercent)) { wastePercent = 0; } // 1. Calculate Base Ground Area var groundArea = length * width; // 2. Calculate Actual Surface Area using Pitch Multiplier var actualArea = groundArea * pitchMultiplier; // 3. Add Waste Factor var totalWithWaste = actualArea * (1 + (wastePercent / 100)); // 4. Calculate Squares (1 square = 100 sq ft) var squares = totalWithWaste / 100; // 5. Calculate Bundles (3 bundles per square) var bundles = Math.ceil(squares * 3); // Display Results document.getElementById("resGroundArea").innerText = groundArea.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 0}); document.getElementById("resActualArea").innerText = actualArea.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 2}); document.getElementById("resTotalArea").innerText = totalWithWaste.toLocaleString(undefined, {minimumFractionDigits: 0, maximumFractionDigits: 2}); document.getElementById("resSquares").innerText = squares.toFixed(2); document.getElementById("resBundles").innerText = bundles; document.getElementById("roofResults").style.display = "block"; }