Metal Roof Calculator
This calculator finds panel count, panel length, and fastener quantities for metal roofing, using panels = ⌈eaveLength ÷ panelCoverage⌉ and panelLength = (run + overhang) × slope factor, with fastener spacing sourced from a manufacturer installation manual.
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Scenario presets
- Panel length
- 16.77 ft
- Total panel length
- 234.8 ft
- Field fasteners
- 238
- Side-lap stitch screws
- 221
- Closure strip needed
- 80 linear ft
How it works
Metal panels run in one piece from eave to ridge along the roof's slope, side by side across the building's length. Panel count depends only on eave length and panel coverage; panel length depends only on run, overhang, and pitch.
panels = ⌈eaveLength ÷ panelCoverage⌉ · panelLength = (run + overhang) × slopeFactor
- Panel coverage — 36" for standard exposed-fastener corrugated/ribbed panels; 12"-16" for standing seam.
- Field fasteners — attach the panel through its flat pan to the framing or deck, at 12" on center per manufacturer spec.
- Side-lap stitch screws — join adjacent panels along their overlapping rib, also at 12" on center.
- Closure strips — seal the panel profile at the eave (and optionally ridge), sold by the linear foot or roll.
Worked example
A garage roof: 24 ft eave, 14 ft run, 12" overhang, 6/12 pitch, standard 36" exposed-fastener panels, ridge closure included.
Panel length. (14 + 1) × 1.118 = 15 × 1.118 = 16.77 ft.
Panel count. 24 ft eave = 288". 288 ÷ 36 = 8 panels.
Total panel length. 8 × 16.77 = 134.2 ft of panel material.
Field fasteners. 16.77 ft = 201.2". 201.2 ÷ 12 ≈ 17 per panel × 8 panels = 136 fasteners.
Side-lap stitch screws. 7 side-laps between 8 panels × 17 screws each = 119 screws.
Closure strip. Eave (24 ft) + ridge (24 ft) = 48 linear ft.
Tips from the field
- Order panels custom-cut to your calculated length when possible — it avoids end-laps and the extra fasteners and sealant they require.
- Confirm your supplier's exact effective coverage width before ordering — even "36-inch" panels vary slightly by manufacturer.
- Buy 5-10% extra fasteners — a few always end up stripped, dropped, or bent during installation.
- Check local wind design requirements before finalizing fastener spacing — high-wind zones often need tighter spacing than the standard 12" on center used here.
What this tool does not do
- Does not model end-lap seams for panels longer than your supplier's maximum length.
- Does not calculate a wind-zone-specific fastener schedule — check a project-specific engineering table for that.
- Does not give a closure-strip bundle or roll count — only the linear footage needed.
For asphalt shingles instead of metal, see the Shingle Calculator. For the rafter geometry behind the run and overhang inputs, see the Rafter Length Calculator.
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Frequently asked questions
These are the questions that come up when a metal roof order needs panel counts, lengths, and fastener quantities that actually match the manufacturer's installation manual.
What is "panel coverage" and why does it matter?
Coverage is the effective width each panel adds to the roof once overlapped with its neighbor — not the panel's raw sheet width. 36" is standard for exposed-fastener corrugated/ribbed panels (per Metal Sales R-Panel/PBR-Panel specs); standing seam panels typically cover 12"-16".
Why does panel type change so much about the calculation?
Exposed-fastener panels (36" coverage) and concealed-fastener standing seam panels (12"-16" coverage) need very different panel counts for the same eave length — a 40 ft eave needs about 14 panels at 36" coverage but 30-40 panels at 12"-16" coverage.
How is panel length calculated?
Panel length = (run + overhang) × slope factor — the same geometry the Rafter Length Calculator uses for a common rafter, since metal panels run from the eave to the ridge along the same slope.
Can I order one panel per roof plane instead of standard lengths?
Yes — many metal roofing suppliers custom-cut panels to your exact slope length, avoiding end-laps entirely. This calculator assumes that (one panel per position, full slope length), which is the more common approach for residential and small commercial jobs.
What if my roof run is too long for a single custom panel?
Very long slopes may need an end-lap between two panels. This calculator doesn't model end-lap seams — if your supplier has a maximum panel length shorter than your calculated panel length, add a minimum 6" overlap (solid deck) per panel run and order accordingly.
Where do the fastener spacing numbers come from?
Field fasteners at 12" on center and side-lap stitch screws at 12" on center both come from Metal Sales Manufacturing Corp.'s R-Panel and PBR-Panel installation manuals, including their UL 580 Wind Uplift listing.
Does high-wind construction need tighter fastener spacing?
Often yes — manufacturers note that high-wind areas may require closer spacing than the standard 12" on center, but the exact number depends on a project-specific wind engineering table. This calculator uses the standard 12" spacing; check your local wind design requirements for anything beyond that.
What is a "side-lap stitch screw" versus a "field fastener"?
Field fasteners attach the panel to the roof framing or deck through the flat pan of the panel. Side-lap stitch screws join two adjacent panels together along their overlapping rib, independent of the framing below.
Do I need closure strips at both the eave and the ridge?
Most installations need closure at both — inside closures at the eave (sealing the underside of the panel profile) and outside closures at the ridge or hip. Toggle "include ridge closure" off if your ridge detail uses a different trim approach.
Why doesn't this calculator give me a closure strip bundle or roll count?
Closures are sold in varying roll or segment lengths depending on the manufacturer — this calculator gives the linear footage needed (eave and, optionally, ridge length) so you can divide by your specific product's packaging.
Does panel width vary between manufacturers even for the "same" panel type?
Yes, slightly — always confirm effective coverage width on your actual product's spec sheet, since profiles like R-Panel, PBR-Panel, and their equivalents from other manufacturers can differ by an inch or more.
How we checked this page
- Written by
- Pitch & Span Editorial
- Reviewed by
- Panel coverage, fastener spacing, and end-lap overlap checked directly against Metal Sales Manufacturing Corp.'s R-Panel and PBR-Panel installation manuals, including their UL 580 Wind Uplift listing.
- Last reviewed
- 2026-07-28
- Publisher
- Pitch & Span
- Scope
- Exposed-fastener metal roofing material estimating
- What we checked
-
- Worked example (24 ft eave, 14 ft run, 6/12 pitch, 36" panels) verified against the live calculator.
- Panel length formula cross-checked against the Rafter Length Calculator's run-and-overhang geometry.
- Fastener spacing (12" field, 12" side-lap) confirmed against the source manufacturer's installation manual rather than a generic estimate.
Cite this calculator
Pitch & Span. "Metal Roof Calculator." Pitch & Span, https://pitchandspan.com/metal-roof-calculator/. Accessed .
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