Metal Roofing Calculator
Count metal roofing panels by coverage width, with order length, panel area, optional eave projection, and a manufacturer-based fastener allowance.
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 order allowance - the allowance is added after the whole-panel layout count, so partial layout panels are rounded before extra material is added.
- Add only known details - open Advanced to add eave projection only when it is not already in the slope measurement, and enter a fastener rate only from the actual panel-system schedule.
- Review the panel schedule - use the total panel count, panels per slope, and cut length for a supplier takeoff; installed pricing belongs in the separate Roof Replacement Cost Calculator.
Metal panels are ordered by the piece at their coverage width, which is the width left after the side lap. A 40 foot wide gable roof using 36 inch coverage panels lays out at 14 panels per slope, or 28 before allowance. With a 10 percent order allowance, that rounds to 31 panels. Enter the measured slope length as the order length, or add an eave projection only when your measurement does not already include it.
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.
Panel order length should follow the actual measured slope and the panel-system eave detail. If your eave-to-ridge measurement already includes the required projection, leave the optional projection field blank. Ridge cap, drip edge, valley, gable trim, closures, clips, and other accessories are product-specific and should come from the supplier takeoff.
Panel Profiles and Coverage Widths
Coverage width sets the panel count. Minimum slope and attachment depend on the exact listed/tested panel system:
| Example profile | Typical coverage | Attachment | Slope note |
|---|---|---|---|
| 5V Crimp | 24 in | Exposed fasteners | ABC lists 3:12 minimum for this product |
| PBU / similar rib panel | 36 in | Exposed fasteners | ABC lists 1:12 minimum for PBU |
| LokSeam standing seam | 12-18 in | Concealed clips | ABC lists 3:12 minimum for LokSeam |
| Other metal panel systems | Product data | Product-specific | Use the exact manufacturer/listing requirement |
These rows are examples, not universal rules for every corrugated, ribbed, or standing-seam product. Confirm coverage, minimum slope, substrate, lap/sealant details, and attachment from the exact panel system.
Why Fasteners Are Not a Fixed Screws-per-Square Number
Metal roof attachment is system-specific. Exposed-fastener panels can specify fastener rows and spacing along the panel, while standing-seam systems use clips or fastening strips. Wind design, substrate, panel gauge, tested assembly, and manufacturer details can all change the schedule.
That is why the calculator does not assume a universal 80 screws per 100 square feet. If your panel schedule gives a usable exposed-fastener rate, enter it in Advanced. Otherwise leave the field blank and use the project or manufacturer schedule directly.
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 installed pricing, use the Roof Replacement Cost Calculator separately. Keep this page focused on the field-panel material takeoff and supplier quote.
How the Panel Count Is Built
The math behind the schedule:
Base layout panels = Panels per slope × number of like slopes
Total panels = Base layout panels × (1 + order allowance %), rounded up
Order length = Measured eave-to-ridge slope length + entered eave projection
Panel area = Total panels × coverage width × order length
Optional exposed fasteners = Panel area / 100 × entered manufacturer/project rate
For hips, dormers, or unequal roof planes, calculate unlike slopes separately. Attachment remains governed by the tested panel system and project conditions.
Code and Manufacturer References
- IRC R905.10 requires metal roof panels to be attached in accordance with the code and manufacturer installation instructions, and it addresses tested wind resistance for metal panel systems.2024 IRC - Metal roof panels
- ABC installation material shows why attachment cannot be reduced to one universal screw rate: one exposed-fastener panel uses specified fastener locations and spacing, while other panel systems use different fastening strips, clips, or load-table requirements.American Building Components - 5V Crimp installation manual
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. Multiply that whole-panel layout count by the number of like slopes, then apply the selected order allowance. A 40 foot wide gable roof in 36 inch coverage panels is 14 per slope, 28 before allowance, and 31 panels after a 10 percent allowance.
What is the minimum pitch for metal roofing?
There is no single minimum pitch for every metal panel product. IRC provisions distinguish lapped and standing-seam systems, and listed/tested products can have their own minimum slopes and lap or sealant requirements. Check the exact manufacturer installation instructions before ordering.
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, order length, panel area, and an optional exposed-fastener allowance when you enter a schedule rate. 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.