Metal Roofing Panel Worked Example: Count Panels for a Gable, Hip, and Metric Roof

This page works through three complete metal roofing panel counts from real dimensions: a simple gable roof, a hip roof, and a metric gable roof. Every number below was checked with independent arithmetic, so you can follow the steps and trust each result.

How many metal roofing panels does a simple gable roof need?

Start with the answer for the example: 22 panels. A 48 ft by 30 ft gable roof with a 5/12 pitch needs 20 panels of cut-to-length metal roofing at 36 in coverage width, and 22 after a 10% waste allowance.

The example roof has a 48 ft wide footprint and a 30 ft long ridge. Each roof plane covers half the width, so the horizontal run per plane is 24 ft. A 5/12 pitch multiplies that run by 1.0833, which gives a slope length of exactly 26.0 ft. Each plane is therefore 30 ft by 26 ft, or 780 sq ft, and the two planes total 1,560 sq ft.

Slope length = run x pitch multiplier

Pitch multiplier = sqrt(1 + (rise / run)^2)

Panels run vertically from eave to ridge. Count across the eave first: 30 ft divided by the 3 ft coverage width gives 10 panels per plane. Count up the slope next: the 26 ft slope fits exactly one 26 ft cut-to-length panel, so there is 1 row. That gives 10 x 1 = 10 panels per plane, or 20 panels for both planes.

Waste covers cutting, handling, and small fitting errors. A simple gable uses 10%: 20 x 1.10 = 22. The order is 22 panels.

What changes if you order 16 ft stock panels instead?

Cut-to-length panels come off the roll at the exact slope length. Stock 16 ft panels need a 6 in end lap wherever two panels stack on one slope, so each stacked panel effectively covers 15.5 ft. Two rows cover 31 ft, which is more than the 26 ft slope, but it still requires 2 rows per plane.

That changes the count from 20 to 40 panels before waste: 10 panels per row x 2 rows x 2 planes. Same roof, same slope, nearly double the panel count. This is why the ordering guide treats cut-to-length and stock lengths as separate decisions.

How do you count panels on a hip roof?

The answer for the example: 33 panels. A 40 ft by 30 ft hip roof with a 6/12 pitch needs 28 panels by exact area, and 33 after a 15% waste allowance for hips.

Hip roofs have triangular and trapezoidal planes, so the per-row count used on a gable does not work here. The area method is the honest choice: convert the footprint to sloped area, divide by the area one panel covers, round up, and add waste.

1. Pitch multiplier for 6/12: sqrt(1 + 0.25) = 1.1180.
2. Sloped roof area: 40 x 30 x 1.1180 = 1,341.64 sq ft.
3. One 3 ft by 16 ft panel covers 48 sq ft.
4. Exact panels: 1,341.64 / 48 = 27.95, round up to 28.
5. Complex roof waste at 15%: 28 x 1.15 = 32.2, round up to 33.

Result: order 33 panels. The hip waste rate is higher because triangular cuts leave offcut waste on every hip plane.

How does a metric panel count work?

The answer for the example: 18 panels. A 12 m by 8 m gable roof with a 6/12 pitch needs 16 panels at 1.0 m coverage width, and 18 after 10% waste.

The method is identical; only the units change. Each plane covers a 6 m run. With the 6/12 pitch multiplier of 1.1180, the slope length is 6 x 1.1180 = 6.7082 m. Each plane is 8 m by 6.7082 m, or 53.6656 m², and the two planes total 107.331 m².

1. Panels per plane: 8 m / 1.0 m coverage width = 8.
2. Cut-to-length panels at 6.7082 m: 1 row up the slope.
3. Exact panels: 8 x 1 x 2 planes = 16.
4. Waste at 10%: 16 x 1.10 = 17.6, round up to 18.

Result: order 18 panels. Use the coverage width the manufacturer states for your panel profile, not the full sheet width. Side laps reduce the covered width, and the count must use the covered width.

Which counting method should you use?

Use the per-row method on roofs with rectangular planes: count across the eave, count up the slope, round each up, then multiply. This is the method in the measuring guide.

Use the area method on hip roofs and roofs with dormers or many valleys, where triangle cuts make per-row counting unreliable. Round the exact count up, then add a waste rate that matches the roof complexity: 10% for simple roofs, 15% for complex ones.

Confirm three manufacturer numbers before ordering: the coverage width (after side lap), the available panel lengths (cut-to-length maximum), and the required end lap for stacked panels. McElroy Metal notes that exposed-fastener panels most often have 36 in coverage while standing seam panels run 16 to 18 in, and that there is no universal fastener pattern, so coverage and fastening details come from the manufacturer, not from a generic table.

What should you double-check before ordering?

• Rake and eave overhangs add slope length. Measure to the panel edge, not the wall.
• Deduct nothing for small vents, then add the waste allowance. Small penetrations do not change the panel count but do not reduce waste either.
• Obstructed sections need extra full-length panels, as Metal Central's ordering guide advises.
• Ordering to the exact count leaves the run short when a slope needs an extra row. Round up at every step before adding waste.
• Keep ridge caps, trim, fasteners, and underlayment on the same order list. Panels alone do not finish the roof.

For the full list of mistakes these checks prevent, see Metal Roofing Panel Mistakes.