How many metal roof panels
A metal roof panel calculator counts by coverage width, not by the panel's overall width: overlapping ribs or seams use up part of each sheet. Divide the eave length (plus the rake overhangs) by the coverage width from the product sheet and round up. The last panel is ripped to fit, and the results show by how much.
| Eave length | 12 in coverage | 16 in coverage | 24 in coverage | 36 in coverage |
|---|---|---|---|---|
| 20 ft | 20 | 15 | 10 | 7 |
| 24 ft | 24 | 18 | 12 | 8 |
| 30 ft | 30 | 23 | 15 | 10 |
| 40 ft | 40 | 30 | 20 | 14 |
| 50 ft | 50 | 38 | 25 | 17 |
Metal roofing calculator: panel length
Panels run from eave to ridge in one piece where possible, so their length is the sloped length of the roof plane. Take the level run (half the width on a gable), add the eave overhang and multiply by the rafter factor for the pitch. Many suppliers cut panels to length; order each slope's length to the nearest inch and leave the gap at the ridge that the ridge cap detail calls for.
Minimum slope for metal roofs
The IRC sets three minimums for metal roof panels in R905.10.2: 3/12 for lapped, non-soldered seams without lap sealant, 1/2/12 with lap sealant, and 1/4/12 for standing-seam systems[1]. Metal roof shingles need 3/12 (R905.4.2)[1]. The panel's own installation guide may set a higher minimum; follow the stricter of the two.
- Under 3/12, the IRC also wants ridges and hips designed as beams[2].
- For the pitch of a single-slope roof, use the shed roof pitch calculator.
Trim and accessories
Eave trim (drip edge) runs along every eave, rake or gable trim up both sides of each slope, and ridge cap along the ridge of a gable. Add closures under the ridge cap and at the eaves to block the panel profile. Fastener patterns come from the panel maker. To compare with shingles, the roof calculator gives squares and bundles, and the roof pitch calculator converts the pitch to degrees.
Frequently asked questions
How does a metal roof panel calculator count panels?
It divides the eave length (plus the rake overhangs) by the panel coverage width and rounds up, then multiplies by the number of roof slopes.
How do I calculate how many metal roof panels I need?
Divide the length along the eave by the panel coverage width and round up, then multiply by the number of slopes.
How long should metal roof panels be?
The level run plus the overhang, times the rafter factor for your pitch. At 4/12 the factor is 1.054.
What is the minimum pitch for a metal roof?
1/4 in per foot for standing seam, 1/2 in per foot for lapped panels with sealant and 3 in per foot without sealant, under IRC R905.10.2.
Is there a metal roof calculator app?
Yes: this page is built to work as one on a phone. It runs in any mobile browser with no sign-up, and you can add it to your home screen from the browser menu.
How many squares is a metal roof?
Panel length × eave length × slopes ÷ 100, in square feet.