Metal Roof Material Calculator — Sheets, Battens, Screws & Ridge
Calculate materials for a metal roof: steel sheet coverage from your roof footprint and pitch, sheet-support battens, sealing-washer screws and ridge caps. Metal sheets are priced per m² of coverage — enter your profile's rate and get the full list.
How many metal roofing sheets do I need?
Work from the true roof area, not the footprint: divide the plan area by the cosine of the pitch. Then divide by the sheet's *cover* width — the part left showing after the side lap, typically 1,000 mm of a 1,100 mm sheet, or 36 in of a 39 in one. Add 10% for cuts at hips, valleys and verges.
What pitch does a metal roof need?
Lower than tile, which is much of the appeal. Profiled steel will run down to about 10°, and standing seam lower still, where concrete tile generally wants 20–22°. Below those figures the laps stop shedding water and start holding it, so the covering decides the pitch as much as the pitch decides the covering.
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Plan the whole job — not just this calculation
Save results to a project: budget and shopping list build themselves, and the whole plan exports as a PDF. Draw your floor plan and room sizes pre-fill the calculators.
How the metal roof estimate works
- 1True roof area: plan area ÷ cos(pitch) — metal works from as little as 7° pitch
- 2Sheet coverage: roof area + 10% waste, priced per m² of effective cover (profile-dependent)
- 3Sheet-support battens at 600 mm centres — 24 in OC — plus counter battens over the underlay
- 4Screws: ~8 per m² — roofing screws with EPDM sealing washers, into battens
- 5Ridge: steel ridge caps at ~1.9 m effective cover per 2 m cap — 6¼ ft per 6½ ft cap, with a 100 mm (4 in) lap
- 6Underlay membrane beneath the sheets: roof area + 15% for laps
Worked example
Gable roof: 10 × 7 m plan (33 × 23 ft), 20° pitch — about a 4:12 slope. Profiled steel sheets, battens at 600 mm (24 in OC).
True roof area: 70 ÷ cos(20°) = 74.5 m² → order 82 m² (880 sq ft) of sheet with 10% waste. Plus 8 rows of battens per side (incl. the eaves batten), ~600 screws (3 boxes of 250), 6 ridge caps and 86 m² (925 sq ft) of underlay.
Frequently asked questions
How do I calculate how much metal roofing I need?
Convert your footprint to true roof area (divide by cos of the pitch), add 10% waste, then divide by your panel's effective cover width to get panel count — or order by m² as most suppliers quote. Panels are usually cut to your slope length, which nearly eliminates end-lap waste.
What is the minimum pitch for a metal roof?
Profiled/corrugated steel sheets: around 7–10° depending on the profile and lap sealing. Standing seam systems can go lower (3–5°). Below the profile's minimum, water can back up the laps — check the manufacturer's stated minimum.
How many screws does a metal roof need?
Roughly 6–8 screws per m² for profiled sheets — one per corrugation crest at eaves and laps, every second crest on intermediate battens. Always use screws with EPDM sealing washers, driven straight and snug, not crushed.
Does a metal roof need battens or a solid deck?
Profiled sheets go on horizontal battens (typically 600 mm centres, 24 in OC) over counter battens and underlay. Standing seam usually wants a continuous deck. The calculator counts battens; switch to the shingle covering if you need deck sheets counted instead.
Do I need underlay under a metal roof?
Yes — condensation forms on the underside of metal sheets on cold nights, and the underlay carries it to the gutter. Use an anti-condensation or breathable membrane, with a ventilated batten gap above it.