Calculate how many shingles, bundles, and roofing materials you need. Get accurate square footage, material lists, and cost estimates for your roofing project.
Roof Area
1342 sq ft
Actual sloped area
Squares
14.8
100 sq ft each
Two sloped sides meeting at a ridge - most common residential roof.
* Estimates based on architectural shingles. Prices vary by region, material quality, and contractor. Does not include tear-off, disposal, or structural repairs.
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
| 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 |
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.
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.
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.
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.
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.
Roof Area
1342 sq ft
Actual sloped area
Squares
14.8
100 sq ft each