What is panel coverage?

The width a panel covers once overlapped — 36 in for many ribbed panels.

6–8 in; more below 3/12 pitch.

How many screws per square?

About 70–80 per 100 sq ft, depending on purlin spacing and wind zone.

Minimum pitch for metal roofing?

Often 3/12 for exposed-fastener panels; 1/2:12 for some standing seam.

Standing seam or exposed fastener?

Standing seam lasts longer with hidden fasteners; exposed fastener is cheaper.

Metal roofing calculator

Roof plane length, roof width, number of planes, panel coverage width, panel length and end lap: you get panels with waste, screws and trim.

Purchase quantity

21 panel

Net measurement: 1291.669 ft² · Waste 5 %

Panels21 panel
Self-drilling screws (6 per m²)3 box
Ridge cap32.808 ft
Rake / gable trim78.74 ft

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How it's calculated (visible formula)

columns = ceil(width ÷ coverage); rows = ceil((plane − lap) ÷ (panel − lap)); panels = columns × rows × planes

Net geometric measurement, no waste.
Adjustable waste % for cuts and breakage.
Purchase rounded up to sellable units (boxes, bags, buckets, boards).

See methodology and formula versions

How to calculate it, step by step

Measure plane length eave to ridge and roof width.
Enter panel coverage width and length.
Work out columns and rows with end lap.
Multiply by planes and add waste.
Add screws, ridge cap and trim.

Worked example: Two planes of 20 × 33 ft, 36 in coverage, 20 ft panels

33 ft ÷ 3 ft = 11 columns
1 row per plane
22 × 1.05 = 24 panels

→ About 24 panels (21 with 1 m coverage), screws and 33 ft of ridge cap.

Common mistakes

Using full panel width instead of coverage.
Short end laps on low slopes.
Screws without neoprene washers.

Pro tips

Start on the side opposite the prevailing wind.
Fasten on the rib or flat per the maker's system.
Use sealant tape on laps at low pitches.
Add underlayment or condensation control over living space.

From calculation to quote

Add labor, overhead and your margin, and generate the professional PDF.

Create quote Calculate margin & tax

FAQs

What is panel coverage?: The width a panel covers once overlapped — 36 in for many ribbed panels.
What end lap?: 6–8 in; more below 3/12 pitch.
How many screws per square?: About 70–80 per 100 sq ft, depending on purlin spacing and wind zone.
Minimum pitch for metal roofing?: Often 3/12 for exposed-fastener panels; 1/2:12 for some standing seam.
Standing seam or exposed fastener?: Standing seam lasts longer with hidden fasteners; exposed fastener is cheaper.
How much does metal roofing weigh?: About 1–1.5 lb per sq ft.

Sources and standards

Maintained by Srikanta M · Formula v1.0.0 · Verified 2026-09-10 · Updated 2026-09-10 · Limits: quantity estimation, not structural design or site supervision.