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Roofing

Metal Roofing Calculator

Work out how many metal panels, screws and trim your roof needs.

ft
ft
The true sloped distance, not the horizontal run. Use the rafter calculator if unsure.
in
Coverage width, not overall width — panels overlap. Most exposed-fastener panels cover 36 in.
Panels needed —
Total linear feet of panel — ft
Screws —

What you'll need to order

Prices vary by region and haul distance. Get quotes from at least two local suppliers.

How this calculator works

panels = eave length × 12 ÷ panel coverage width

Use the coverage width, not the overall panel width — a panel sold as 39 inches wide typically covers only 36 inches once lapped. Getting this wrong leaves you a panel short on every roof.

Switch the site to metric — the control is in the footer — and your inputs, your results and the tables below follow. The formula, the constants, the guidance text and the sources stay in US units on purpose: that is how the standards they come from are written, and restating them would detach each figure from the document you are meant to be able to check it against.

Where these numbers come from

Cited to a specific edition on purpose — table numbers and values move between cycles. Confirm against whichever edition is enforced locally.

Worked example

With eave length 40 ft, slope length (eave to ridge) 16 ft, panel coverage width 36 in, this calculator returns 13.33 .

Panels needed for roofs of common size

Each row is a link that fills in the calculator above. Send one and the other end sees the same figures you do.

JobSizePanels needed
Small shed 12 ft × 8 ft × 36 in 4.00
Two-car garage 24 ft × 14 ft × 36 in 8.00
House gable side 40 ft × 16 ft × 36 in 13.33
Pole barn 60 ft × 24 ft × 36 in 20.00
Porch roof 20 ft × 8 ft × 24 in 10.00

Use coverage width, not overall width. A panel sold as 39 in usually covers 36 once lapped.

Frequently asked questions

How many metal roofing panels do I need?

Divide the eave length in inches by the panel coverage width. A 40 ft eave with 36 inch coverage panels needs 14 panels per slope, rounding up.

What length should I order metal panels?

Most suppliers cut to order, so specify the exact slope length plus 2 to 3 inches of eave overhang. A single full-length panel per slope avoids horizontal laps, which are the most common leak point.

How many screws does metal roofing need?

Roughly 80 per square for exposed-fastener panels — about 1 screw per square foot including laps and trim. Standing seam uses hidden clips instead and the count differs entirely.

What is the minimum pitch for metal roofing?

Exposed-fastener corrugated panels need 3/12 or steeper. Standing seam with sealed seams can go down to 1/4 in 12 on some systems. Below the manufacturer minimum, the warranty is void.

Use the metal roofing calculator on your site, free

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