Metal roofing panels run from the eave to the ridge in one piece, so they are ordered by count and cut length. Each profile covers a set width once the panels overlap, which the makers publish; that width sets the count.
How to use this calculator
- Choose a gable roof (two sides) or a shed roof (one slope).
- Enter the length along the eave and the width of the building, overhangs included, and the pitch.
- Pick the panel profile you plan to use.
Worked examples
A garage roof in R-panel
Roof: Gable (two sides) · Length along the eave: 24 ft · Building width, with overhangs: 26 ft · Pitch: 4 in 12 · Panel: R-panel or PBR (36 in coverage)
- Panels
- 16 panels, 13 ft 10 in long
- Panels
- 16
- Screws with sealing washers
- 550
- Ridge cap, 10.5 ft pieces
- 3
- Eave trim, 10.5 ft pieces
- 6
- Rake trim, 10.5 ft pieces
- 8
- Panels per side
- 8 panels
- Roof area
- 658 sq ft
- Roofing squares
- 6.6 squares
A house in standing seam
Roof: Gable (two sides) · Length along the eave: 50 ft · Building width, with overhangs: 32 ft · Pitch: 6 in 12 · Panel: Standing seam, 16 in
- Panels
- 76 panels, 18 ft 1 in long
- Panels
- 76
- Ridge cap, 10.5 ft pieces
- 5
- Eave trim, 10.5 ft pieces
- 10
- Rake trim, 10.5 ft pieces
- 8
- Panels per side
- 38 panels
- Roof area
- 1,789 sq ft
- Roofing squares
- 17.9 squares
A lean-to shed roof
Roof: Shed (one slope) · Length along the eave: 16 ft · Building width, with overhangs: 10 ft · Pitch: 3 in 12 · Panel: Classic rib / ag panel (36 in)
- Panels
- 6 panels, 10 ft 6 in long
- Panels
- 6
- Screws with sealing washers
- 150
- Eave trim, 10.5 ft pieces
- 2
- Rake trim, 10.5 ft pieces
- 4
- Panels per side
- 6 panels
- Roof area
- 165 sq ft
- Roofing squares
- 1.6 squares
A barn in corrugated
Roof: Gable (two sides) · Length along the eave: 60 ft · Building width, with overhangs: 36 ft · Pitch: 4 in 12 · Panel: Corrugated, 2.5 in
- Panels
- 68 panels, 19 ft 2 in long
- Panels
- 68
- Screws with sealing washers
- 1,850
- Ridge cap, 10.5 ft pieces
- 6
- Eave trim, 10.5 ft pieces
- 12
- Rake trim, 10.5 ft pieces
- 8
- Panels per side
- 34 panels
- Roof area
- 2,277 sq ft
- Roofing squares
- 22.8 squares
Panel coverage
- R-panel or PBR: 36 inches of coverage per panel.
- Classic rib or ag panel: 36 inches.
- Corrugated, 2.5 in: about 21.333 inches.
- Standing seam: 12 inches, 16 inches or 18 inches panels.
Cut length, laps and pitch
Panels are ordered cut to the slope length plus the eave overhang, about 1 to 2 inches. Where a slope is too long for one panel, makers lap the panels end to end, 6 inches for Metal Sales and 12 inches for Fabral.
Each profile has a lowest pitch: Metal Sales allows its R-panel down to 1 in 12 but asks for 3 in 12 for its rib and corrugated panels. The calculator warns when your pitch is below it.
Screws and trim
Exposed-fastener panels take about 80 screws per square (a hundred square feet), with stitch screws every 12 inches along the side laps. Standing seam is held by concealed clips instead.
Trim comes in pieces of 10.5 ft that lap 3 inches, so each covers about 10.25 ft. The calculator counts ridge cap, eave trim and rake (gable) trim.
Common questions
How do I calculate how many metal roof panels I need?
Divide the length along the eave, in inches, by the panel's coverage width and round up; that is one side. A gable roof needs the same again for the other side.
How long should metal roofing panels be?
The length of the slope from eave to ridge plus the eave overhang of 1 to 2 inches. The calculator works out the slope from the building width and the pitch.
How many screws do I need for a metal roof?
About 80 screws per square of exposed-fastener panels, plus stitch screws along the side laps.
What is the minimum pitch for a metal roof?
It depends on the panel: 1 in 12 for Metal Sales R-panel and 3 in 12 for its corrugated. Check your panel's installation guide.