Estimate metal roofing panels from your roof area and panel coverage width, plus screws and the ridge, eave, gable and valley trim — with the panel-length and coverage gotchas that trip up first-time metal roof orders. Using asphalt shingles instead? Use the roofing material calculator.
How will you enter the roof size?
Actual sloped surface area, not the flat footprint. Measure it on the roof area calculator.
Order to the slope (eave to ridge), not the horizontal run. Custom-cut panels can’t be lengthened on site.
Along the eave (ft).
Horizontal, eave to ridge (ft).
Sets slope length.
Quick estimate. Slope length = run × pitch multiplier; panel length is set from it. For multi-plane, hip or L-shaped roofs, measure on the roof area calculator and use the area mode; the roof pitch calculator explains the multiplier.
Net width covered, not the overall panel width.
Exposed-fastener gets a screw count; standing seam uses clips along the seams instead.
~10% for simple runs; more for hips, valleys and cut-up roofs.
Trim lengths (lineal)
Ridge cap, eave/drip, gable/rake and valley trim, by the linear foot. Leave at 0 if unknown.
Your own local price — no prices are baked in. Leave blank to skip cost.
An estimating aid using typical exposed-fastener coverage and fastener rates, all adjustable. Confirm the exact panel length, coverage width, fastening and trim profiles with your supplier before ordering — panels are usually custom-cut and can’t be shortened or lengthened on site.
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Measuring the roof?
Get the sloped area on the Roof Area Calculator and the slope on the Roof Pitch Calculator (pitch, angle and the multiplier that sets panel length). Going with asphalt shingles instead of metal? The Roofing Material Calculator builds the shingle bill of materials.
Counting metal panels the right way
A metal roof is a panel system, so this metal roof calculator works differently from asphalt squares and bundles — whether your panels are steel, aluminium or a traditional tin roof, it’s the panel geometry that drives the order. Two things trip up almost every first-time order: using the wrong width, and ordering the wrong length.
First, panel coverage width is not the same as panel width. The sheet is wider than the roof it covers, because the edges overlap (corrugated, rib, 5V) or lock into a seam (standing seam). A 36″ corrugated panel often covers about 34″; a 16″ standing-seam panel covers 16″ of roof from steel that’s wider. Counting from the nominal width under-counts panels and leaves you short, so this calculator works from the coverage width you enter.
Second, order panel length to the slope, not the run. Panels are usually custom-cut to length to avoid leak-prone horizontal seams, and a panel cut too short can’t be fixed. The slope length is the horizontal run times the pitch multiplier, plus a small eave overhang.
slope length = run × pitch multiplier (+ overhang) panel area = coverage width × panel length panels = ceil( roof area × (1 + waste%) ÷ panel area )
Start from the actual sloped area — measure it on the roof area calculator for a real multi-plane roof — or use the footprint-plus-pitch mode here for a quick gable estimate.
Screws for exposed-fastener, clips for standing seam
Exposed-fastener panels are screwed through the face into the deck or purlins, and the common estimating rule is about 80 screws per roofing square (100 ft²) — roughly 1.5 per square foot once the field, the laps and the trim are counted. So a 1,800 ft² roof needs about 1,440 screws; round up and add a few percent for drops.
exposed-fastener screws ≈ roof area ÷ 100 × 80
Standing-seam panels are held by concealed clips along the seams rather than face screws, so the per-square screw count doesn’t apply — clips are sized by panel length and clip spacing. When you choose standing seam, the calculator notes this rather than giving a misleading screw figure.
Trim: ridge, eave, gable and valley
Metal roofs are finished with matching lineal trim, ordered by the linear foot and usually in 10 ft lengths: ridge cap along the ridge, eave or drip trim along the eaves, gable or rake trim down the rakes, and valley metal in any valleys. Order panels and trim in the same batch so the colour lots match. This tool totals the trim lineal from the lengths you enter.
Exposed-fastener vs standing seam at a glance
Exposed-fastener
Standing seam
Fastening
Face screws (visible)
Concealed clips
Typical coverage
24–36″
12–20″
Min. pitch (typical)
~3:12
can run lower
Relative cost
Lower
Higher
Install
DIY-friendlier
Usually professional
These are general ranges; the actual coverage width, minimum slope and fastening for your panel are set by the profile and manufacturer — confirm them before ordering.
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Frequently asked questions
How much metal roofing do I need?
Work from the sloped area and divide by the area each panel covers. The catch: coverage width is less than overall width (a 36″ panel may cover ~34″), and panel length is ordered to the slope (eave to ridge), not the horizontal run. This tool uses coverage width and slope length so the count reflects the roof, not the raw panel size.
What’s the difference between panel width and coverage width?
Panel width is the overall sheet; coverage (net/effective) width is how much roof one panel covers after the overlap or seam. Coverage width is smaller and is the one to count from — using nominal width leaves you short. Always use the coverage width your supplier lists for the profile.
How many screws per square for a metal roof?
For exposed-fastener panels, about 80 screws per square (100 ft²), roughly 1.5/ft². An 1,800 ft² roof is about 1,440 screws — round up, add a few percent. Standing seam uses concealed clips instead, sized by panel length and clip spacing, so the screw rule doesn’t apply.
What length should I order panels?
To the slope length — eave to ridge along the surface, not the horizontal run — since panels are custom-cut and can’t be lengthened. Slope length = run × pitch multiplier, plus a small eave overhang. The footprint-plus-pitch mode derives it; otherwise enter the panel length you’ll order and confirm with your supplier.
Exposed-fastener vs standing seam — what’s the difference?
Exposed-fastener (corrugated, 5V, rib) screws through the face: cheaper, DIY-friendlier, gaskets need inspection. Standing seam locks at raised seams on concealed clips: pricier, usually professional, best leak resistance and lower minimum pitch. Coverage and fastening differ, so the calculator handles each.
What trim does a metal roof need?
Matching lineal trim by the foot (usually 10 ft lengths): ridge cap, eave/drip, gable/rake and valley metal. Order panels and trim in the same batch for colour-lot consistency. Enter your edge lengths and the tool totals the trim lineal.
How is this different from the other roofing tools?