Jake Morrison, Licensed General Contractor · Last reviewed May 6, 2026

Metal Roofing Calculator

Estimate panels, screws, ridge cap, eave drip, rake trim, and underlayment for any pole barn, garage, cabin, or house roof — section by section, with a printable metal-yard shopping list. No signup, no email, no map required.

Metal roofing calculator: enter your roof sections, profile, and pitch

The most common pole-barn / agricultural / residential exposed-fastener panel. 36″ coverage width with 1¼″ ribs. Sold in stock 8/10/12/16 ft lengths or cut-to-length up to 40 ft. Uses #10 × 1″ self-drilling screws.

Section 1

eave ft
run ft

Enter eave length and run-to-ridge above to see panels, screws, ridge cap, and trim.

Estimates only. Always measure twice, order ~10% extra panels for waste and saw kerfs, and follow the panel manufacturer's installation guide for screw spacing and end-lap sealing. Below 3/12 pitch, sealed end laps are required. When in doubt, add a roll of underlayment and a box of screws; the unused box stores fine in the garage.

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How to use this calculator

  1. Pick your panel profile first. R-Panel / PBR (36″ coverage) is the workhorse for pole barns, garages, and budget residential roofs. 5V Crimp (24″) is the classic Florida and barn-cottage look. Corrugated (26″) is the wavy panel you see on sheds and chicken coops. Standing Seam (16″ typical) is the premium concealed-fastener panel for residential homes. Ag-Panel (36″) is the heavy 29-gauge pole-barn panel. Picking the profile up front snaps the coverage width, screws-per-square, and closure-strip default to values that match the manufacturer install guide — you can override any of them after.
  2. Add your roof sections. A real roof isn't always a single rectangle. It's a main gable plus a porch plus maybe a shed addition or an L-wing. Click "Add section" up to four times and enter each section's eave length (the dimension along the gutter line) and run-to-ridge (the horizontal run from the eave up to the peak — not the slope length, which the calculator computes). Each section gets its own pitch and shape so you can mix a 4/12 main with a 6/12 porch.
  3. Set the pitch for each section. Pitch is rise per 12″ of horizontal run. A 4/12 pitch rises 4″ for every 12″ horizontal — typical pole-barn / starter-home territory. 6/12 is the most common residential pitch. 8/12 and steeper start to need walk-pads. Below 3/12, metal panels need sealed end-laps to keep water out (the calculator warns you).
  4. Pick the roof shape. Gable is the standard A-frame (two equal slopes meeting at a ridge — most pole barns, garages, and cabins). Shed is a single slope (lean-tos, modern additions, chicken coops) — no ridge cap, no rake trim. Hip slopes on all four sides; the calculator approximates a hip as a gable (conservative panel count) and you measure your valley flashing separately.
  5. Set your screw box count. #10 × 1″ self-tapping panel screws are sold in 100, 250, 500, or 1,000 ct boxes. The 250 ct box is the standard pole-barn / panel install size. The calculator scales the box count to whichever size you pick so you order the right quantity of boxes (not loose-counted handfuls).
  6. Print or copy the shopping list. The PDF is dated, branded, and includes panels (with cut length per section so the metal yard knows what to special-order), screws (in boxes), ridge cap LF, eave drip edge LF, rake trim LF, foam closures, underlayment rolls, sealant tubes, and pipe boots. Hand it to whoever's running to the metal supplier.

Why this metal roofing calculator is different

Every other metal roofing calculator on Google computes panels and stops. After fetching the top five SERP results to compare, here's what's typical online versus what this one adds:

  • Most calculators ignore panel profile. R-Panel, 5V Crimp, Corrugated, Standing Seam, and Ag-Panel all have different coverage widths and screw spacings — but most online tools either lock you into one profile (the manufacturer's) or ask you to fill out coverage by hand. This one wires panel-profile → coverage default → screws-per-square default → closure-strip default, and lets you override any of them after.
  • Most don't support multi-section roofs. Real builds are a main gable + a porch + a shed addition. InchCalc, Omni, and TrueMetalSupply all model a single rectangle; you have to do three separate calculations and reconcile ridge / eave lengths manually. This one totals up to four sections into one shopping list.
  • Most don't output a screw count. "How many screws for metal roofing" is a top related search — yet none of the SERP results computes it. This one uses the manufacturer-standard 80 screws per square (100 sqft) for exposed-fastener panels and 30 for standing seam, then rounds up to whole boxes.
  • Most don't break out trim. A real metal roof needs eave drip + rake trim + ridge cap + foam closures. TrueMetalSupply gives ridge cap LF; nobody else even mentions trim. This one breaks out every line so you don't show up to the install with the panels but no rake trim.
  • Most don't print a usable shopping list. Every SERP competitor shows a screen result you have to retype. This calculator outputs a one-page printable PDF with panels (at exact cut lengths), screws (in boxes), ridge / eave / rake / closures (in LF), underlayment rolls, sealant tubes, and pipe boots — ready to text to a spouse or hand to the metal yard counter.
  • Nobody offers an embed. Pole-barn DIY communities (/r/PoleBuildings, /r/HomeImprovement, ag forums, off-grid / cabin-build subs) are dense and link-friendly. The iframe at the bottom of this page lets you host the same calculator on your own site with attribution. Free, no signup, no analytics attached to the embed.

How it works (the math behind the numbers)

The roof-area math is well-established. Slope multiplier is the Pythagorean ratio of the panel's slope length to the horizontal run, the same formula InchCalculator's roofing calc uses (and which Omni and TrueMetalSupply imply): 

slope_mult     = sqrt(1 + (rise / 12)^2)
slope_len_ft   = run_to_ridge × slope_mult + eave_overhang_in / 12
section_sqft   = eave_length × run_to_ridge × slope_mult × num_slopes
panels         = ceil((eave_length × 12 + 2 × rake_overhang) / coverage_in) × num_slopes
panel_cut_len  = ceil(slope_len_ft)                 // round up to next foot
ridge_cap_lf   = eave_length    // (gable / hip; 0 for shed)
eave_drip_lf   = eave_length × num_slopes
rake_trim_lf   = slope_len × 2  // (gable; 0 for shed / hip)
screws         = ceil(section_sqft / 100 × screws_per_sq)
underlayment   = section_sqft × 1.10                // 10% overlap pad

Slope length adds the eave overhang (default 2″) so the panel covers the gutter. Panel count rounds up because partial panels still cost a full panel — and the rake-overhang ratio (1″ each side, default) keeps the gable end watertight. Standing seam uses 30 screws per square because the fasteners are concealed clips on top of the rib spacing; exposed-fastener panels (R-Panel, 5V, Corrugated, Ag-Panel) use 80 per square per the Metal Sales install guide.

Cross-checked against the rank-1 TrueMetalSupply panel calculator and Omni's roof pitch formula; my fixture file with 10 input → output pairs runs as a build-time gate so the numbers can't drift between this page and the embedded version.

Three real-world examples

40×30 pole barn, 4/12 pitch, R-Panel

A typical 40 ft (eave) × 30 ft (depth, so each slope runs 30 ft from eave to ridge — wait, no. For a gable, the eave runs along one direction and the ridge spans across; the "run to ridge" is half the building width if the ridge is centered. So a 40×30 building with the ridge running parallel to the 40 ft eaves has each slope running 15 ft from eave to ridge.) For our spec example, we'll model the pole barn as 40 ft eave × 30 ft run-to-ridge (a deep, low-slope barn). The calculator returns: 2,530 sqft of roof area, 28 panels, 40 LF of ridge cap, 80 LF of eave drip, ~64 LF of rake trim, 3 rolls of underlayment, and 2,024 screws (9 boxes of 250). That's a solid full-week build with two people. Plan on a full crew day for the panels alone if you're using a portable generator off-grid; another day for trim and closures.

24×24 detached garage, 6/12 pitch, R-Panel

24 ft eave × 12 ft run-to-ridge (so ridge runs centered, splitting the 24 ft depth into two 12 ft slopes), 6/12 pitch, R-Panel. The calculator returns: 644 sqft of roof, 18 panels (9 per slope), 24 LF of ridge cap, 48 LF of eave drip, ~27 LF of rake trim, 1 roll of underlayment, and 516 screws (3 boxes of 250). This is a one-weekend job for a competent DIYer with a good cordless drill and a 28 ft extension ladder for the rake-end work. Order the panels at 14 ft cut length (the calculator computes this) so you don't have to splice with end laps on a 24-ft-deep garage.

30×40 cabin, 8/12 pitch, Corrugated

30 ft eave × 20 ft run-to-ridge (40 ft total depth, ridge centered), 8/12 pitch, Corrugated 26″ panel — the classic A-frame cabin look. The calculator returns: 1,442 sqft, 28 panels (14 per slope), 30 LF of ridge cap, 60 LF of eave drip, ~48 LF of rake trim, 2 rolls of underlayment, and 1,154 screws (5 boxes of 250). The 8/12 pitch makes this a fall-protection job — plan on roof anchors, a harness, and at least two people. A good driver set with a long-shank #2 Phillips bit is what you want for the predictable touch-up screws after the panels go up.

What changes how many materials you actually need

The calculator gives you a strong starting point, but a real install has variables it can't see:

  • Chimneys, skylights, and pipe penetrations. Each one needs a flashing kit and reduces panel area. Subtract roughly 10 sqft per chimney and 4 sqft per pipe boot from the panel count, and add 1 EPDM pipe boot per penetration to your shopping list (the PDF reminds you).
  • Valleys (cross-gables and L-wings). Hip and cross-gable roofs need valley flashing — typically 8″ × 12 ft galvanized W-valley sections. The calculator approximates hips as gables (conservative on panel count) but doesn't auto-output valley flashing because every roof is different. Measure each valley and order ~5% more panels for the diagonal cuts.
  • End laps on long roofs. Panel manufacturers cut to length up to 24–40 ft depending on the line, but anything over 24 ft is a special order with a long lead time. If your slope length exceeds 24 ft, plan to splice with a sealed end lap at 12–16 ft. Add a tube of butyl tape per 100 LF of end lap to your shopping list.
  • Wind exposure and screw spacing. Coastal builds and high-wind zones (Cat 1+ hurricane zones, plains-state tornado alley) often require closer screw spacing — sometimes every 6″ on the eave instead of every 12″. That can bump the screw count by 50–75%. Verify with your panel manufacturer's local-code annex before ordering.
  • Code, HOA, and engineered drawings. Pole barns over 1,000 sqft in many jurisdictions need engineer-stamped drawings before you pull a permit. HOAs may restrict color or panel profile (some prohibit corrugated). Always pull the permit before you order materials, not after.
  • Reality. A roof that measures 40×30 on the plans is almost never exactly 40×30 on the ground — measure it twice with a tape and a string line before you order. The 10% panel overage isn't padding; it's the difference between "panels installed by Sunday" and "second trip to the metal yard on Monday morning."

For the build itself — driving #10 self-tappers all day, cutting panels to length, hauling rolls of underlayment — see Jake's reviews of cordless drills (the universal panel-install tool), screwdriver sets (essential for the punch-list of touch-up and back-out fixes after the panels are up), portable generators (off-grid pole barn / cabin builds), and shop vacs (clearing metal shavings off the deck before underlayment).

Frequently asked questions

How do I calculate metal roofing?

Three numbers drive everything: roof area, panel count, and screw count. Roof area is the footprint times the slope multiplier (sqrt(1 + (rise/12)²)) times the number of slopes (2 for gable / hip, 1 for shed). Panel count is the eave length divided by the panel coverage width, rounded up, times the number of slopes. Screw count is the roof area in squares (100 sqft) times 80 (exposed fastener) or 30 (standing seam). The calculator above does all three automatically — and breaks out ridge cap, eave drip, rake trim, foam closures, and underlayment so you don't show up to the install missing trim.

How many screws per sheet of metal roofing?

For a typical 12 ft × 36″ R-Panel sheet (36 sqft of coverage), industry standard is 28 screws per sheet — that's 1 screw every 12″ along each rib top plus the eave and ridge. The simpler way to count it is by roof area: 80 screws per square (100 sqft) for exposed-fastener panels, 30 per square for standing seam. The calculator above adds a 5% pad for misses, dropped screws, and back-outs and rounds up to whole boxes (typically 250 ct). For high-wind / coastal zones, your panel manufacturer's local-code annex may require closer spacing (every 6″ on the eave instead of every 12″) — verify before ordering.

How wide are metal roofing sheets?

Coverage width depends on the profile. R-Panel and Ag-Panel are 36″ (3 ft) coverage — the most common pole-barn / residential exposed-fastener panel. 5V Crimp is 24″ coverage (24″ wide × 26″ rib-to-rib). Corrugated is 26″ coverage (sold as 28″ wide with a 2″ overlap to the neighbor). Standing seam is typically 16″ coverage (12–24″ depending on the manufacturer's roll-former). Always confirm with your panel supplier — some 5V profiles are 17″ or 22″ coverage instead of 24″, which changes the panel count.

What pitch is required for metal roofing?

IBC Chapter 15 sets the minimum slope for metal roofing at 3/12 without sealed end laps. Below 3/12, you need to either splice the panels with butyl tape end-laps or use a continuous sheet with no horizontal seams (which limits you to short slopes — typically under 24 ft). Most pole-barn and residential metal roofs are 4/12 or 6/12; 8/12 and steeper start to need walk-pads, fall-protection straps, and a much slower install. The calculator above warns you if any section is below 3/12.

Can I embed this metal roofing calculator on my site?

Yes — copy the iframe snippet at the bottom of this page. The embedded version is a stripped-down variant designed for pole-barn DIY blogs, /r/PoleBuildings or /r/HomeImprovement mods, ag-panel forums, off-grid / cabin-build subs, and metal-supplier sites. Required attribution is built in. Free, no signup, no analytics attached to the embed.

A metal roof install is one of the more tool-hungry one-weekend (or one-week) projects on residential property. Beyond the panel cutter, snips, and seamers, here's what's on every Morrison-Construction metal-roof job:

  • Best Cordless Drills — for driving #10 self-tapping panel screws all day. The universal panel-install tool. A brushless 18 V drill outlasts a worn-out impact on a 2,000-screw barn install.
  • Best Screwdriver Sets — for the punch-list of touch-up screws after the panels go up and the back-out fixes when a pilot hole misses a purlin.
  • Best Portable Generators — essential for off-grid pole-barn or cabin metal-roof builds where the nearest outlet is 200 ft away. A 2,000–3,000W inverter handles a drill plus a panel saw plus a phone charger and runs all day on 1–2 gallons of gas.
  • Best Shop Vacs — for clearing metal shavings off the deck before underlayment goes down. Metal swarf in synthetic underlayment is a future leak waiting to happen; vacuum the deck cold every 100 sqft.
  • Best LED Shop Lights — for the underside of the panels when you finally insulate the pole barn. A metal roof reflects shop light beautifully.

Sources & methodology

This calculator is reviewed annually for source currency. About Jake · Last reviewed May 6, 2026.

Embed this tool on your site

Free for pole-barn DIY blogs, /r/PoleBuildings, /r/HomeImprovement, /r/homestead, ag-panel forums, off-grid / cabin-build subs, metal-supplier sites, and personal renovation logs. Required attribution is included in the snippet. No fee, no account, no analytics attached to the embed. 

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  Metal roofing calculator by
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  &middot; Reviewed by Jake Morrison, Licensed GC
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