Roof Pitch and Common Rafter Calculator
6.00 / 12 · 26.57°
Pitch angle
26.57°
Multiplier 1.1180
Common rafter
14 ft 5 9/16 in
Tail 1 ft 1 7/16 in
Cuts
26.57° plumb
63.43° seat
Roof area
1,215 ft²
12.15 squares
Shingle bundles
41
3 bundles per square + 10% waste
Sheathing / felt
42 sheets
4 underlayment rolls
Delivery weight
4,914 lb
2,229 kg · 70 lb bundles, 46 lb sheets, 28 lb rolls
Rise and run are scaled from the span, overhang, and pitch. The small triangle is the pitch ratio.
| Item | Net | Waste | Order | Unit price | Line total | Source Spec Material / Tool |
|---|---|---|---|---|---|---|
| Architectural shingle bundles | 12.15 squares | 10% | 41 bundles | USD | $1,722.00 | Source Spec Material / Tool |
| 4x8 CDX sheathing | 38.0 sheets | 10% | 42 sheets | USD | $1,176.00 | Source Spec Material / Tool |
| Underlayment rolls | 1,215 ft² | overlap allowance | 4 rolls | USD | $220.00 | Source Spec Material / Tool |
| Ridge cap bundles | 42.0 ft ridge | — | 2 bundles | 25 ft per bundle | — | Source Spec Material / Tool |
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| Pitch | Degrees | Multiplier | Rafter | Squares | Bundles | Sheets |
|---|---|---|---|---|---|---|
| 4.0/12 | 18.43° | 1.054 | 13 ft 7 5/8 in | 11.46 | 38 | 40 |
| 6.0/12 | 26.57° | 1.118 | 14 ft 5 9/16 in | 12.15 | 41 | 42 |
| 8.0/12 | 33.69° | 1.202 | 15 ft 6 9/16 in | 13.06 | 44 | 45 |
| 12.0/12 | 45.00° | 1.414 | 18 ft 3 9/16 in | 15.37 | 51 | 53 |
Show the deterministic formula
Angle = arctan(rise ÷ 12). Multiplier = √(1 + (rise ÷ 12)²). Gable run = span ÷ 2 − ridge thickness ÷ 2. Rafter length = (run + horizontal overhang) × multiplier.
Plumb cut = pitch angle. Seat cut = 90° − pitch angle. Area uses both slopes on a gable and one slope on a shed, and it includes a rake overhang equal to the eave overhang.
Bundles = ceiling of squares × 3 × 1.10. Sheets = ceiling of area × 1.10 ÷ 32. Rolls use 360 ft² effective coverage. Delivery weight plans 70 lb per bundle, 46 lb per sheet, and 28 lb per roll, then the header converts that pound total at 1 lb = 0.45359237 kg.
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This sheet is an estimate for ordering and layout discussion. It is not a sealed design. Confirm the quantities with a licensed local professional and the authority having jurisdiction before you buy or build.