Metal Roofing Calculator
Calculate how many 3x12-foot metal roofing panels you need for your roof area, plus total material cost.
How this calculator works
Metal roofing panels come in a standard 3 ft × 12 ft size covering 36 square feet each in most exposed-fastener systems. This calculator divides your roof’s surface area by that coverage figure to get the panel count, rounding up since panels are ordered as whole units cut to length.
Formula: Panels = Roof area (sq ft) ÷ 36 sq ft per panel.
Worked example
A 30 ft × 20 ft roof section (600 sq ft of surface area):
- Panels: 600 ÷ 36 ≈ 16.67 → rounds up to 17 panels
- At $75/panel, that’s $1,275.00.
Coverage reference
| Roof surface area | Metal panels needed (3x12 ft) |
|---|---|
| 15 ft × 10 ft | 5 panels |
| 30 ft × 20 ft | 17 panels |
| 60 ft × 40 ft | 67 panels |
How to measure your roof
Measure each roof plane’s length and width and add the areas together, accounting for the actual sloped surface rather than the ground footprint. Since most suppliers roll-form metal panels to your exact run length rather than selling only fixed stock lengths, provide your roof’s actual plane dimensions when you place the order rather than relying on this calculator’s panel count alone.
Frequently asked questions
What panel size does this calculator assume?
A standard 3 ft × 12 ft metal roofing panel, covering 36 square feet each. Panels come in other standard lengths, but 12 ft is a common stock length for exposed-fastener and standing-seam residential panels.
Are metal roofing panels sold in fixed lengths or cut to size?
Most suppliers roll-form panels to your exact run length rather than selling only fixed stock lengths, so you typically order panels cut to the length of each roof plane rather than cutting a 12 ft panel down yourself. This calculator's 36 sq ft coverage still applies since it's based on the panel's 3 ft width times whatever length you order.
How much overlap is built into the panel coverage figure?
The 36 sq ft per panel already accounts for the panel's rated 3 ft width, which is the exposed coverage width after side-lap overlap between adjacent panels — not the panel's raw material width before overlap. That's why you don't need to add extra width allowance on top of this calculator's result.
How many screws does a metal roof panel need?
Exposed-fastener panels typically use screws spaced every 12-24 inches along each rib in the field of the roof, with tighter spacing at eaves, ridges, and panel end laps. A rough planning figure is 20-30 screws per 3 ft × 12 ft panel, though your specific panel profile and local wind-load code may call for more.
How much waste should I add for a metal roof?
10% covers standard cutting waste around valleys, hips, and penetrations like vents or chimneys. Complex roofs with lots of dormers, valleys, or angle changes typically need more, since metal panels can't be pieced together as flexibly as shingles can.
Estimates only. Verify quantities with your supplier before purchasing.