Enter the area under the roof and its pitch. You get the sloped roof area, the squares to order with extra for cuts, the shingle bundles, and the rolls of synthetic underlayment.
Each row includes 10% extra for cuts, hips and starter, at 3 bundles per square.
| Footprint and pitch | Roof area | Squares | Bundles |
|---|---|---|---|
| 1,000 sq ft at 4/12 | 1,054 sq ft | 11.6 | 35 |
| 1,500 sq ft at 6/12 | 1,677 sq ft | 18.4 | 56 |
| 2,000 sq ft at 6/12 | 2,236 sq ft | 24.6 | 74 |
| 2,000 sq ft at 8/12 | 2,404 sq ft | 26.4 | 80 |
| 2,500 sq ft at 6/12 | 2,795 sq ft | 30.7 | 93 |
| 3,000 sq ft at 10/12 | 3,905 sq ft | 43.0 | 129 |
A pitched roof has more surface than the footprint under it. The slope factor is the length of the rafter for each foot of run: √(rise² + 12²) ÷ 12, so 1.118 at 6/12 and 1.414 at 12/12. This is the same factor the roofing cost calculator uses.
A square is 100 sq ft of roof. The tool adds 10% for cutting at hips, valleys and edges, then counts 3 bundles per square, the standard for architectural and 3-tab shingles, rounded up.
Synthetic underlayment rolls are rated at 1,000 sq ft (10 squares) before laps; the tool allows 10% for side and end laps.
Sources:
Quantities are for planning and ordering. Check the plan, the supplier’s product data and local code before you buy; for structural concrete, follow the drawings.
Most shingles come 3 bundles to a square, which covers 100 sq ft of roof. A 1,500 sq ft footprint at a 6/12 pitch is 1,677 sq ft of roof; with 10% extra that is 18.4 squares, or 56 bundles.
A house with a 2,000 sq ft footprint and a 6/12 pitch has about 2,236 sq ft of roof surface, so 24.6 squares to order with 10% extra, or 74 bundles. A steeper roof has more surface over the same footprint.
Pitch multiplies the footprint by the slope factor: 1.054 at 4/12, 1.118 at 6/12, 1.202 at 8/12 and 1.414 at 12/12. A 12/12 roof needs about 41% more shingles than a flat measurement of the same house.
A synthetic underlayment roll is usually rated at 1,000 sq ft, 10 squares, before laps. The 1,677 sq ft roof above takes 2 rolls once laps are allowed for. Ice and water shield at eaves and valleys is counted separately.
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