Inputs
White theme • Client‑side onlyExample Data
Click “Load Example” above to populate these values.
| Parameter | Value | Unit |
|---|---|---|
| Units | Imperial | ft |
| Roof Type | Gable | — |
| Building length | 48 | ft |
| Building width | 32 | ft |
| Pitch rise per 12 | 4 | in/ft |
| Eave overhang | 0.75 | ft |
| Ridge allowance | 0.25 | ft |
| Rake overhang | 0.5 | ft |
| Effective cover width | 3 | ft |
| Continuous panels | No | — |
| Stock panel length | 12 | ft |
| End lap deduction | 0.5 | ft |
| Waste factor | 7 | % |
Results
Enter inputs and press Calculate.
| Metric | Value | Unit |
|---|
Formulae Used
- Slope factor (imperial pitch): \( S = \sqrt{1 + (rise/12)^2} \)
- Slope factor (metric percent): \( S = \sqrt{1 + (percent/100)^2} \)
- Run per slope: shed ⇒ run = width, gable ⇒ run = width / 2
- Slope length: \( L_s = run \times S + eave + ridge \)
- Panels across: \( N_p = \left\lceil \dfrac{length + 2 \cdot rake}{w_{eff}} \right\rceil \)
- Segments along slope (if not continuous): \( n = \left\lceil \dfrac{L_s - e}{\ell - e} \right\rceil \), where \( \ell \) is stock length, \( e \) is end-lap deduction.
- Total panels: \( N = N_p \times n \times \text{slopes} \)
- Waste applied: multiply totals by \( (1 + \frac{\%}{100}) \)
Assumes rectangular plan, panels run eave→ridge, and net coverage equals effective width.
How to Use
- Select units and roof type. For custom, set plane count.
- Enter building length, building width, and pitch (rise per 12 or percent).
- Add allowances: eave, ridge, and rake.
- Enter effective cover width, or check “compute” and supply nominal and side lap.
- Choose continuous panels or supply stock length and end-lap deduction.
- Set a waste percentage to cover cutting, damage, and contingencies.
- Press Calculate, then export CSV or print the results to PDF.
Tip: For very long runs, consider segmenting with controlled lap placement to minimize offcuts.
FAQs
It is the true net width each panel covers after side-lap engagement and rib geometry. Use manufacturer data; otherwise compute: effective = nominal − side‑lap width.
Yes, gable roofs have two planes. The calculator multiplies panels across by the number of slopes (2 for gable, 1 for shed, or your custom value).
Each lap joint reduces useful length by the lap deduction. The segment count formula uses stock length minus lap deduction to ensure full coverage.
This version supports rise per 12 (imperial) or percent (metric). Convert degrees to percent with: percent = 100 × tan(degrees).
Common practice is 5–10% depending on roof complexity, cutting strategy, on‑site handling, and supplier packaging. Increase for many obstructions or penetrations.
No. This tool counts panel sheets. Order ridge caps, eave/drip trims, closures, fasteners, and sealants separately per manufacturer guidance.
The calculator assumes a rectangular plan with straight eaves and ridge. For hips, valleys, dormers, or skew, split the roof into rectangles and sum the results.