Metal Roof Calculator
Enter your roof dimensions and panel width to get the number of metal panels you need for one roof plane, with waste included.
What your result means
Panels is how many run side by side to cover one roof plane, with waste added. Each panel runs the full slope length from eave to ridge, so order them about 6 inches longer for the ridge fold-over. A gable roof has two planes, so double this for the whole roof. Ridge cap, eave, gable, and valley trim are ordered separately.
How to use this calculator
- Measure roof length (along the eave) and width (along the slope, eave to ridge).
- Standard metal panel is 36 in wide. Some are 24 in or 18 in.
- Use 10% waste.
- Read total sqft and panel count.
- Order ridge cap and flashing separately.
The formula
Panels lay side by side across the eave run, so divide the eave length in inches by the panel width and round up. Add your waste percentage and round up again. Each panel runs the full eave-to-ridge slope length. Double the count for a two-sided gable roof.
Worked example
Say one roof plane is 30 ft along the eave and 16 ft up the slope, with 36-inch panels and 10% waste. Across the 30 ft eave you need 30 divided by 3, so 10 panels, then 11 with waste. Each runs about 16 ft, and you'd order them a few inches longer for the ridge. Double it to 22 for both sides of a gable.
Standard metal panel widths
| Panel type | Coverage width |
|---|---|
| Standard standing seam | 36 in (3 ft) |
| Narrow standing seam | 24 in (2 ft) |
| Architectural / specialty | 18 in (1.5 ft) |
Tips & gotchas
- Standard panel coverage width is 36 inches.
- Each panel runs the full length from eave to ridge, with no horizontal seams.
- Order panels about 6 inches longer than the slope for the ridge fold-over.
- Order matching trim separately: ridge cap, eave, gable, and valley flashing.
- Grab at least one extra panel for the piece you'll dent during install.
Frequently asked questions
How wide is a standard metal roof panel?
36 inches, or 3 ft. Some specialty panels run 24 or 18 inches wide.
How long should metal panels be?
Each panel runs the full slope from eave to ridge in one piece, no horizontal seams. Order them a few inches long for the ridge fold.
Can I install metal roofing over shingles?
Often yes, if local code allows. Don't stack more than two roofs, though.
What gauge metal roof should I buy?
26 gauge is the standard residential choice. 24 gauge is heavier and more durable.
How long does a metal roof last?
40 to 70 years for galvanized steel, and 50-plus for aluminum or copper.
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