Quick Start - Common Projects
Complex Roof Calculator
Shingle Type
Compare Shingle Types for Your Roof
Roof Type
Two sloped sides meeting at a ridge - most common residential roof.
Roof Dimensions
Materials Needed
Cost Estimate
* Estimates based on architectural shingles. Prices vary by region, material quality, and contractor. Does not include tear-off, disposal, or structural repairs.
How It's Calculated
1. Base Area
40 ft × 30 ft = 1200 sq ft
2. Pitch Multiplier (6/12)
1 / cos(arctan(6/12)) = 1.118
3. Actual Roof Area
1200 × 1.118 = 1342 sq ft
4. With 10% Waste
1342 × 1.10 = 1476 sq ft = 14.8 squares
Roof Pitch Reference
| Pitch | Angle | Multiplier | Walkable? |
|---|---|---|---|
| 2/12 | 9.5° | 1.014 | Easy |
| 4/12 | 18.4° | 1.054 | Easy |
| 6/12 | 26.6° | 1.118 | Moderate |
| 8/12 | 33.7° | 1.202 | Caution |
| 10/12 | 39.8° | 1.302 | Difficult |
| 12/12 | 45.0° | 1.414 | Difficult |
Frequently Asked Questions
How do I measure my roof?
Measure the length and width of each roof section at ground level, then multiply by the pitch factor. For a gable roof, measure the base footprint. The pitch multiplier converts flat area to actual sloped area. Use satellite imagery or climb up safely to verify.
What is a roofing square?
A roofing square equals 100 square feet of roof area. Materials like shingles are sold by the square. Three bundles of standard 3-tab shingles typically cover one square. Architectural shingles may require 4-5 bundles per square.
How much waste should I add?
Add 10-15% for simple gable roofs, 15-20% for complex roofs with valleys and dormers. Hip roofs need more waste due to angled cuts. First-time DIYers should add an extra 5-10%. Better to have extra than run short mid-project.
What is roof pitch?
Roof pitch is the slope expressed as rise over run. A 6/12 pitch means the roof rises 6 inches for every 12 inches of horizontal run. Higher pitches shed water and snow better but are harder to walk on and require more materials.
How long do shingles last?
3-tab shingles: 15-20 years. Architectural/dimensional shingles: 25-30 years. Premium architectural: 30-50 years. Metal roofing: 40-70 years. Lifespan depends on climate, ventilation, installation quality, and maintenance.