Shingle Quantity Calculator
Calculate the number of shingle bundles and squares needed for your roofing project based on roof dimensions and pitch.
Formula
1. Pitch Multiplier = √(1 + (Pitch ÷ 12)²)
2. Flat Area = Length × Width × Number of Slopes
3. Sloped Area = Flat Area × Pitch Multiplier
4. Total Area = Sloped Area × (1 + Waste% ÷ 100)
5. Squares = Total Area ÷ 100
6. Bundles = ⌈Squares × 3⌉
Assumptions & References
- One roofing square covers 100 square feet of roof surface.
- Standard three-tab or architectural shingles require 3 bundles per square (each bundle covers ~33.3 sq ft).
- The pitch multiplier converts horizontal (plan) area to actual sloped surface area using the Pythagorean theorem: √(1 + (rise/run)²).
- A waste factor of 10% is typical for simple gable roofs; use 15–20% for complex roofs with hips, valleys, or dormers.
- Pitch is expressed as rise per 12 inches of horizontal run (e.g., 6:12 means 6 inches of rise for every 12 inches of run).
- This calculator does not account for ridge caps, starter strips, or hip/valley shingles, which should be purchased separately.
- Reference: Roofing Contractor Magazine; National Roofing Contractors Association (NRCA) guidelines.