Roof Shingle Calculator
Calculates true roof surface area from ground footprint and pitch multiplier, determining exact roofing squares (100 sq ft = 1 square), shingle bundles (3 bundles per square), starter strip rolls, and ridge caps.
Formula
Roof Area = Ground Area × Pitch Multiplier; Squares = Roof Area ÷ 100; Bundles = Squares × Bundles/Square
1. Ground Footprint = Length × Width 2. Pitch Multiplier = √(1 + (Pitch ÷ 12)²) 3. True Surface Area = Ground Footprint × Pitch Multiplier 4. Total Area with Waste = True Surface Area × (1 + Waste %) 5. Roofing Squares = Total Area with Waste ÷ 100 6. Bundles to Order = Ceil(Roofing Squares × Bundles per Square (3 or 4))
Inputs
- Home Footprint Length (Including Overhangs)
- Home Footprint Width (Including Overhangs)
- Roof Pitch Slope (Rise / 12" Run)
- Shingle Style
Worked example
Gable roof (50 ft × 30 ft footprint) with 6/12 pitch slope and architectural shingles.
Outcome: True roof surface area is 1,677 sq ft (16.77 squares). Adding 10% waste equals 18.45 squares (1,845 sq ft). Multiplying by 3 bundles/square gives 55.35 bundles, rounding up to 56 full shingle bundles.
What is a "square" of roofing?
In the roofing industry, a "square" is a unit of measurement equal to 100 square feet of roof surface. Standard asphalt shingles are packaged so that 3 bundles cover exactly 1 square.