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.
Shingle Bundles Needed:
Roof Area:
How to Use This Tool
Enter the length and width of your roof's footprint.
Enter your roof pitch (rise in inches per 12 inches horizontal — common pitches are 4-9).
Enter the waste factor (10% for simple roofs, 15% for complex roofs).
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.