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🛠️ DIY

Roofing Calculator

Roofing materials are sold by the 'square' (100 sq ft). This calculator accounts for roof pitch (slope increases material), waste factor for cuts and mistakes, and gives you the exact number of shingle bundles and underlayment squares needed.

How to Use This Tool

  1. Enter the length and width of your roof's footprint.
  2. Enter your roof pitch (rise in inches per 12 inches horizontal — common pitches are 4-9).
  3. Enter the waste factor (10% for simple roofs, 15% for complex roofs).
  4. Click Calculate to get your material quantities.

The Formula

Actual Roof Area = Footprint Area x Pitch Multiplier where Pitch Multiplier = SQRT(1 + (rise/12)^2). Squares = Area / 100. Bundles = Squares x 3 (standard shingles).

Why It Matters

Your roof measures 2,000 sq ft with a 6/12 pitch. After pitch multiplier (1.25) and 10% waste, you need 22 squares of shingles. At $35/square, the shingle cost is ~$770.

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