Re-roofing? Estimate the squares and shingles you need.
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Roofers measure in squares — 100 square feet of roof. Take the house footprint including overhangs and multiply by the pitch multiplier, which accounts for the slope (1.118 for a 6/12 roof).
Asphalt shingles usually come three bundles per square. Add 10% waste for simple gable roofs and 15% or more for hips, valleys and dormers.
| Units | Feet & inches |
| Building length (ft or m) | 40 |
| Building width (ft or m) | 30 |
| Eave overhang (in or cm) | 12 |
| Roof pitch (rise per 12) | 6 |
| Waste allowance | 10% |
| Price per square (optional) | 0 |
| Currency | $ |
| Roofing squares | 16.67 squares |
| Bundles of shingles (3 per square) | 50 |
| Roof area | 1,502.6 sq ft · 139.6 m² |
| Pitch multiplier | 1.118 (6/12, 26.6°) |
| Underlayment rolls (4 squares each) | 5 |
16.67 squares; 50.
| Units | Metres & centimetres |
| Building length (ft or m) | 12 |
| Building width (ft or m) | 9 |
| Eave overhang (in or cm) | 30 |
| Roof pitch (rise per 12) | 8 |
| Waste allowance | 10% |
| Price per square (optional) | 0 |
| Currency | $ |
| Roofing squares | 17.33 squares |
| Bundles of shingles (3 per square) | 52 |
| Roof area | 1,564.8 sq ft · 145.38 m² |
| Pitch multiplier | 1.202 (8/12, 33.7°) |
| Underlayment rolls (4 squares each) | 5 |
17.33 squares.
With a single-storey footprint of 2,000 sq ft and 6/12 pitch, about 22–25 squares including overhangs and waste.
Usually 3 bundles for standard 3-tab and architectural shingles.
The factor that converts flat footprint area to sloped roof area: √(1 + (rise ÷ run)²).
10% for gable roofs, 15–20% for complex roofs.