Metal Roofing Calculator
Panels across ceil from roof length over coverage width. Panels up slope ceil from width over panel length. Waste multiplies the grid. Estimate only, not a permit, code check, or engineered design.
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How to estimate metal panels
- Enter eave length and slope length in one unit.
- Enter panel coverage width and stock panel length in that same unit.
- Set waste from 0 to 40 percent for hips, valleys, and cull.
- Read roof area, squares, panels across, panels up slope, and panels to buy.
Metal roof panel count
Grid of coverage panels with waste
| Roof area | length × width |
|---|---|
| Squares | area / 100 |
| Across | ceil(length / panelWidth) |
| Up slope | ceil(width / panelLength) |
| Buy | ceil(across × up × (1 + waste/100)) |
| Omitted | Hips, valleys, flashings, and fasteners |
What this metal panel count covers
One rectangular roof plane with constant panel coverage. Dormers and hips need extras. Pitch helpers sit on roof pitch. Shingle bundles sit on shingles. Snow load sketches sit on roof snow load.
How panels to buy are computed
area = length × width. across = ceil(length / panelWidth). up = ceil(width / panelLength). panels = ceil(across × up × (1 + waste/100)). Use coverage width from the manufacturer, not the untrimmed coil width.
Standing seam versus exposed fastener
Both styles still need a coverage width. Standing seam clips and exposed screws change labor, not this grid math. Underlayment and ridge cap are separate line items. Plane area from pitch is on roof area.
Use cases
A 40 by 20 plane with 3 ft coverage and 10 ft panels at 10% waste. Comparing two coverage widths. Not a sealed roofing plan.
Limits
No hip/valley breakout and no flashing lengths. Estimate only, not a permit, code check, or engineered design. Nothing is uploaded.