Metal Roofing Calculator
Count metal roofing panels by coverage width, with order length, panel area, and screws - for standing seam, corrugated, and R-panel profiles.
The horizontal width along the eave that panels lay across, side by side. Measure one slope.
The slope distance from eave up to ridge - this sets the panel order length. Use the Roof Pitch Calculator if you only have the flat run.
How to Use
- Measure one slope - enter the eave width and the eave-to-ridge length for a single slope.
- Pick the roof shape - gable doubles the slope; for a hip, run each differently shaped slope separately and add them.
- Choose the coverage width - this is the width the panel covers after the side lap, not its edge-to-edge size.
- Set the waste factor - metal waste runs higher on hips and valleys because of the diagonal cuts.
- Review the panel schedule - use the total panel count, panels per slope, and cut length for a supplier takeoff; installed pricing belongs in the Roof Replacement Cost Calculator.
Metal panels are ordered by the piece at their coverage width - the width the panel covers after the side lap, not its edge-to-edge size. A 40 foot wide gable roof in classic 36 inch coverage panels takes 14 panels per slope, about 30 total with 10 percent waste, each cut to the eave-to-ridge length plus a 2 to 4 inch overhang. Enter your roof width and slope length above for the full panel schedule.
Nominal Width vs Coverage Width
How Metal Roofing Panels Are Counted
Metal roofing is counted by the panel, not by the square. Panels run from eave to ridge in one piece, laid side by side across the width of the roof. Because each panel overlaps its neighbor at a rib, what matters for counting is the coverage width - the width left after the lap - not the panel edge-to-edge size. Divide the eave width by the coverage width and round up to get the panels per slope; multiply by the number of slopes and add waste for the total.
The order length is the eave-to-ridge slope distance plus a small overhang at the eave, usually 2 to 4 inches. Ridge cap, drip edge, valley, and gable trim are ordered separately: ridge cap comes in lengths that lap, so a 40 foot ridge takes about 14 pieces of 3 foot cap with overlaps. This calculator sizes the field panels and their fasteners; add trim from your supplier once the panel run is set.
Panel Profiles and Coverage Widths
Coverage width sets the panel count; the profile sets the minimum pitch and how it fastens:
| Profile | Coverage width | Fastening | Minimum pitch |
|---|---|---|---|
| Corrugated (round wave) | 24-36 in | Exposed screws, 1-2 rib lap | 3:12 |
| R-panel / PBR | 36 in | Exposed screws, 1 rib lap | 3:12 (1:12 with closures) |
| 5V crimp | 24 in | Exposed screws | 3:12 |
| Snap-lock standing seam | 12-18 in | Concealed clips | 3:12 |
| Mechanically-seamed standing seam | 12-24 in | Concealed clips | 1/2:12 |
Exposed-Fastener vs Standing Seam
Exposed-fastener panels - corrugated, R-panel, and 5V - screw straight through the face into the deck or purlins, using screws with a bonded EPDM rubber washer, roughly 80 screws per square. They are the least expensive metal roof and the most DIY-friendly, but the rubber washers dry out and back out over time, so the fasteners need inspection and re-sealing about every 15 to 20 years.
Standing seam locks adjacent panels together over concealed clips, with no holes through the face of the roof. Nothing to re-seal, the cleanest look, and the lowest achievable pitches - a mechanically-seamed system can go down to a half-in-twelve slope. It costs more per square and usually wants a professional crew with a seaming tool, but it is the longest-lived metal roof.
Panel Quantity vs Installed Pricing
This calculator estimates field-panel quantities from coverage width and cut length. It does not estimate tear-off, labor, underlayment, flashing, trim, permits, or installed price.
For an installed metal roof cost estimate, use the Roof Replacement Cost Calculator. Keep this panel schedule for the material takeoff and supplier quote.
How the Panel Count Is Built
The math behind the schedule:
Total panels = Panels per slope × slopes × (1 + waste %), rounded up
Order length = Eave-to-ridge length + ~3 in overhang
Panel area = Total panels × coverage width × order length
Screws = Panel area / 100 × 80 (exposed-fastener profiles)
Screw counts apply to exposed-fastener panels; standing seam uses concealed clips instead, spaced per the manufacturer. For a hip roof, run each differently shaped slope separately and add the results.
Code Note
- Metal roof systems are rated for wind uplift by a standard static air-pressure test, which is how manufacturers publish the allowable panel spans and clip or screw spacing for a given wind zone. Ask your supplier for the tested assembly that matches your local wind load rather than sizing fasteners by rule of thumb.ASTM E1592 - Structural Performance of Sheet Metal Roof and Siding Systems
Next Steps
A panel count starts from accurate slope data and a valid pitch:
Related Calculators
Metal roofing panels start from accurate area and pitch data. Browse the construction calculator collection.
Frequently Asked Questions
How many metal roofing panels do I need?
Divide the eave width of one slope by the panel coverage width and round up for the panels per slope, then multiply by the number of slopes and add 10 to 20 percent for waste. A 40 foot wide gable roof in 36 inch coverage panels is about 14 per slope, 30 total with 10 percent waste. Each panel is cut to the eave-to-ridge length plus a small overhang.
What is the minimum pitch for metal roofing?
Standing seam can go very low - a mechanically-seamed system down to about a half-in-twelve. Exposed-fastener panels (corrugated, R-panel, 5V) need a minimum 3/12 pitch to keep water away from the screw penetrations, though some R-panels reach 1/12 with sealed closures. Always check the manufacturer specification for your panel.
Is a metal roof louder in rain?
With solid sheathing (plywood or OSB) and underlayment beneath the panels, a metal roof is no louder than shingles. The noise concern applies mainly to agricultural buildings where panels attach directly to purlins with no decking.
Can you install metal roofing over existing shingles?
Often yes. Metal panels can go over one layer of existing shingles on furring strips (battens) that create an air gap, saving tear-off labor and disposal. Check local codes - some jurisdictions require tear-off regardless.
Does this calculator estimate installed metal roof cost?
No. It calculates field-panel quantity, panels per slope, cut length, covered area, and an exposed-fastener screw allowance. Installed pricing includes labor, tear-off, underlayment, flashing, trim, permits, and regional rates; use the Roof Replacement Cost Calculator for that separate intent.
How long does metal roofing last?
Service life varies by panel system, coating, climate, maintenance, and installation quality. Confirm the product warranty and maintenance requirements rather than using lifespan as a panel-count input.