Metal Roofing Calculator
Figure metal roof panels for a gable or shed roof: how many panels, the cut length, screws or clips, and every piece of trim.
How it's calculated
Panels are counted by dividing the eave length (plus rake overhangs) by the panel's coverage width. Panel length is the run from eave to ridge plus the eave overhang, multiplied by the pitch multiplier.
Exposed-fastener panels use about 80 screws per square. Standing seam panels are held with clips, figured at your clip spacing along every panel. Trim is counted in 10'-6" pieces with a 6" lap, so each piece covers 10 ft.
Worked example
A 40 × 24 ft gable building with 4/12 pitch, 12" eaves and 6" rakes needs 14 panels per side of 36" R-panel, cut about 13'-9" long: 28 panels, around 900 screws, 5 pieces of ridge cap and 9 of eave trim.
Field notes
- Measure each side from eave to ridge on the actual roof before ordering. Panels are cut to length and not returnable.
- Exposed-fastener panels usually need at least 3/12 pitch; many standing seam systems go lower.
- Install closures at the eave and ridge to keep out wasps, birds and wind-driven rain.
- Over solid decking, use a high-temperature synthetic underlayment under metal.
Common questions
- How many screws per sheet of metal roofing?
- For a 36" panel on purlins at 24", about 20–25 screws per 12 ft panel. A planning number is 80 screws per 100 sq ft.
- What is the coverage of an R-panel?
- 36" net coverage. The extra width overlaps the next panel.
- Can I put metal roofing over shingles?
- Often yes, over one layer, with purlins or a slip sheet, if local code and the panel maker allow it.