How to calculate metal roofing panels
Panel length = eave to ridge + eave overhang
Example: a 40 ft eave with 36 in R-panel needs 480 / 36 = 13.3, so 14 panels per side, 28 total. Most suppliers cut panels to the inch, so order exact lengths.
Panel types compared
| Panel | Coverage | Fasteners | Material per sq ft |
|---|---|---|---|
| R-panel / PBR | 36 in | Exposed screws | $2.50 to $4.50 |
| Corrugated | 24 to 26 in | Exposed screws | $2.00 to $3.75 |
| Standing seam | 12 to 18 in | Hidden clips | $4.50 to $9.00 |
Want installed pricing instead? Use the metal roof cost calculator.
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Numbers look right? A licensed roofer can measure on site and give you an exact price.
Trim you will need
- Ridge cap along the peak, with foam closures under it.
- Eave trim (drip edge) along the bottom.
- Rake or gable trim along the sloped edges.
- Valley, sidewall and endwall flashing where roofs meet walls or each other.
Minimum pitch for metal
Exposed-fastener panels generally need at least 3/12. Many standing seam systems are rated down to 1/2:12 or even 1/4:12 with sealed seams. Check your pitch with the roof pitch calculator.
Sources and further reading
- Metal Construction Association
- 2021 International Residential Code, Chapter 9: Roof Assemblies
- National Roofing Contractors Association (NRCA)
Frequently asked questions
How many metal roofing panels do I need?
Divide the eave length in inches by the panel's coverage width and round up. Do this for each roof side.
How many screws per metal roofing panel?
Plan on about 70 to 90 screws per 100 sq ft for exposed-fastener panels, placed at every purlin in the flat next to each rib.
Can I put metal roofing over shingles?
Often yes, over one layer of shingles with purlins or a slip sheet, if local code allows. Check for rot first.
Is metal roofing cheaper than shingles?
Exposed-fastener metal can cost about the same installed. Standing seam usually costs 2 to 3 times more but lasts much longer.