Metal Roof Panel Calculator
Measure slope length from eave edge to ridge, or use footprint + pitch below.
Roofing
Metal Roofing Calculator
Quick answer: panels per side = eave length (in) ÷ panel coverage width, rounded up; panel length = slope length + eave overhang. A 40 ft gable roof with 15 ft slopes and 36 in R-panels needs 14 panels per side (28 total) cut to 15 ft 2 in, covering 12 squares.
Estimate exposed-fastener R-panel or standing seam metal roofing for gable and shed roofs: panel count and cut length, linear feet, squares, a rough screw count, ridge cap, and edge trim.
One roof plane
How to calculate metal roofing panels
Metal panels run from eave to ridge, so a roof plane is covered by a row of full-length sheets laid side by side. The eave length sets how many sheets you need; the slope length sets how long each one is. Unlike shingles, you order each panel cut to a specific length, so getting the slope right matters more than the area.
Panels/side = ⌈Eave (in) ÷ coverage (in)⌉
Panel length = slope length + eave overhang · Squares = eave × slope × planes ÷ 100
- Measure the eave length of each plane, including any gable (rake) overhang at both ends.
- Find the slope length. Measure from the eave edge to the ridge on the roof, or calculate it: (half the building width + horizontal eave overhang) × √(1 + (pitch ÷ 12)²).
- Divide eave length by net coverage — 36 in for R-panel, 12–18 in for standing seam — and round up.
- Add the panel overhang the manufacturer specifies at the eave to get the cut length, and round up to the inch.
- Count squares (100 ft²) from eave × slope × number of planes, then multiply by screws per square for exposed-fastener systems.
- Add trim: ridge cap equals the ridge length; eave trim runs the eaves; rake (gable) trim runs both sloped edges of every plane.
Worked example
A 30 ft wide pole barn has a 4/12 gable roof with 12 in eave overhangs and 1 ft gable overhangs on a 40 ft building (42 ft eave). It gets 36 in R-panel with a 2 in panel overhang.
- Slope length: (15 + 1) × √(1 + (4 ÷ 12)²) = 16 × 1.0541 = 16.87 ft
- Panel length: 16.87 ft + 2 in = 17.03 ft → order 17 ft 1 in
- Panels: 504 in ÷ 36 = 14 per side, 28 total = 478 linear ft
- Area: 42 × 16.87 × 2 = 1,417 ft² = 14.2 squares; screws ≈ 14.17 × 80 = 1,134; ridge cap 42 ft
Panels per side by eave length and coverage
Number of panels for one roof plane, rounded up. The last column is the area each linear foot of panel covers.
| Coverage width | 20 ft eave | 30 ft eave | 40 ft eave | 50 ft eave | ft² per linear ft |
|---|---|---|---|---|---|
| 36 in (R-panel / PBR) | 7 | 10 | 14 | 17 | 3.00 |
| 24 in | 10 | 15 | 20 | 25 | 2.00 |
| 18 in (standing seam) | 14 | 20 | 27 | 34 | 1.50 |
| 16 in (standing seam) | 15 | 23 | 30 | 38 | 1.33 |
| 12 in (standing seam) | 20 | 30 | 40 | 50 | 1.00 |
Metal roofing tips and common mistakes
- Use net coverage, not sheet width. An R-panel sheet is wider than 36 in because the side lap overlaps the next sheet. Divide by the published coverage width.
- Check the minimum slope. Each panel profile has a minimum pitch in its installation guide; low-slope roofs often need a standing seam profile or sealed laps. Exposed-fastener panels are typically not rated for very low slopes.
- Measure every plane. Rafter lengths often differ by an inch or more across a long building. Measure at both gable ends and the middle before ordering cut-to-length panels.
- Long runs need splicing or expansion detail. Panels over about 30–40 ft can be hard to ship and handle, and long standing seam runs need floating clips for thermal movement. Ask your supplier.
- Squares for underlayment. Synthetic underlayment rolls are sold by area; use the squares figure plus 10–15% for laps. Many codes and manufacturers require underlayment under metal panels — check local code.
- Hips and valleys change everything. This tool covers rectangular gable and shed planes. Hip roofs need panels cut on the diagonal, which adds waste; count those planes separately in the roof area calculator.
Metal roofing FAQ
How do I calculate how many metal roof panels I need?
Divide the eave length in inches by the panel's coverage width and round up; that is the panel count for one side. A 40 ft eave covered with 36 in R-panels needs 480 ÷ 36 = 13.3, so 14 panels per side and 28 for a gable roof.
How long should metal roof panels be?
Panel length is the slope length from eave edge to ridge plus the eave overhang the manufacturer specifies, often 1 to 2 in past the drip edge. Most suppliers cut panels to the inch, so a 15 ft slope with a 2 in overhang is ordered at 15 ft 2 in.
How many screws per square of metal roofing?
Exposed-fastener panels typically use roughly 70 to 80 screws per 100 square feet, depending on purlin spacing and the manufacturer's pattern. A 12 square roof at 80 per square needs about 960 screws, plus trim screws. Standing seam panels use concealed clips instead.
What is the coverage width of R-panel metal roofing?
Standard R-panel and PBR panels cover 36 inches (3 ft) per sheet after the side laps. Standing seam panels commonly cover 12, 16, or 18 inches. Always use the net coverage width from the product sheet, not the overall sheet width.
How much ridge cap do I need for a metal roof?
A simple gable roof needs ridge cap equal to the ridge length, which is usually the eave length. For a 40 ft gable roof that is 40 linear feet; with 10 ft pieces lapped about 6 in, plan on 5 pieces. Hips add their own length.
How we built this calculator: results use the standard volume, area, and coverage formulas shown on this page, with typical U.S. material densities, bag yields, and waste factors that you can override. Written and checked by the YardsCalculator editorial team. Last reviewed: October 2026.