Shingles Calculator

A roofing square equals 100 square feet. Divide total roof area by 100. Example: 2,400 sq ft roof = 24 squares. Measure length x width of each roof section, add together. For pitched roofs, multiply flat area by pitch multiplier: 4/12 pitch = 1.054x, 6/12 = 1.118x, 8/12 = 1.202x, 12/12 = 1.414x. Always add 10-15% waste factor for cuts, starter strips, and mistakes.

Standard 3-tab shingles: 3 bundles per square (covers 100 sq ft). Architectural/dimensional shingles: Usually 3 bundles per square, but some heavier styles need 4 bundles. Designer shingles: Often 4-5 bundles per square. Always check manufacturer specifications. One bundle typically covers 33.3 sq ft (for 3-bundle squares). Example: 24 square roof with 3-bundle shingles = 72 bundles total.

Waste factor depends on roof complexity: Simple gable roof: 10% waste. Hip roof or multiple valleys: 15% waste. Complex roof with dormers, valleys, angles: 20% waste. Steep pitch (over 8/12): Add 5% extra. Also order extra bundles for: Ridge caps (1 bundle per 35 linear feet), starter strips (1 bundle per 100 linear feet), future repairs. Better to have 1-2 extra bundles than run short mid-job.

Ridge caps cover roof peaks and hips. Measure total linear feet of ridges and hips. Standard coverage: 1 bundle of ridge cap covers 35 linear feet (pre-cut caps) or 1 bundle of regular shingles cut into caps covers 35 linear feet. Calculate: Linear feet / 35 = bundles needed. Example: 80 feet of ridge = 2.3 bundles, round to 3. Hip roofs need caps for all hips plus ridge. Pre-cut ridge caps recommended - faster installation, better seal, professional look.

3-tab shingles: Flat, uniform appearance, single layer, 20-25 year warranty, lighter (3 bundles/square), cheaper ($90-150/square). Architectural/dimensional: Multi-layered, textured 3D look, 30-50 year warranty, heavier and more durable, better wind resistance, higher quality ($150-250/square). Architectural shingles add curb appeal, last longer, better warranty. For most homes, architectural shingles worth the extra cost for longevity and appearance.

From ground (safer): Measure house length and width. Calculate footprint. Multiply by pitch factor (1.054 for 4/12, 1.118 for 6/12, etc.). On roof: Measure each roof plane length x width in feet. Add all sections together. Include dormers, overhangs. Don't subtract small vents/chimneys. Pitch factor accounts for slope increasing actual surface area vs. flat footprint. Use roof pitch app or measure rise over run. Professional measurement recommended for complex or steep roofs.

Possible but not recommended in most cases. Building codes typically allow maximum 2 layers. Pros: Saves labor and disposal costs. Cons: Adds weight (structural concern), hides deck damage, shortens new shingle life, voids some warranties, looks less professional, harder future removal. Best practice: Strip to deck, inspect/repair sheathing, install new underlayment, then shingles. Only re-roof over existing if: 1 layer present, deck is sound, surface is flat, local codes permit, budget constraints critical.