Roofing Calculator
Calculate exactly how many roofing squares of shingles you need, accounting for roof pitch, type, and waste.
How It Works
Applies pitch factor (√(1+(rise/12)²)) to building footprint, doubles it for a gable roof, adds waste, and divides by 100 for squares.
Formula
Pitch Factor = √(1+(Rise/12)²)
Roof Area = Footprint × Pitch Factor × 2
Squares = Area × (1+Waste%) ÷ 100
Example
40×30 ft home, 4:12 pitch, 15% waste:
2,530 sq ft × 1.15 / 100 = 29.1 squares
When to Use This Calculator
Use before ordering shingles, verifying contractor estimates, or planning a DIY roofing project.
Common Mistakes to Avoid
- Not using pitch factor — steep pitches dramatically increase actual area vs footprint.
- No waste for ridges and valleys — complex roofs need 15–20%.
- Wrong pitch measurement — measure with a level and tape on actual roof.
Frequently Asked Questions
What is a roofing square?
100 sq ft of roof surface. Standard 3-tab shingles = 3 bundles/square.
Bundles per square?
3-tab: 3 bundles. Architectural: 3–4 bundles. Check manufacturer spec.
Shingle lifespan?
3-tab: 15–20 years. Architectural: 25–30 years. Class 4 impact-resistant: 40+ years.
Roof over old shingles?
Most codes allow one layer over existing. Two or more must be torn off.
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Last Updated: July 4, 2026