A perforated sheet is defined by three things: the hole shape, the hole size and the pitch (the spacing between holes). Together they set the open area — and open area is what most buyers are really choosing, because it governs flow, light, weight and how much strength is left in the sheet.
What "open area" means and why it matters
Open area is the share of the sheet that is hole rather than metal, given as a percentage. A sheet at 40% open area is 40% holes. More open area means more air, liquid, light or sound passes through, and the sheet is lighter — but there is less metal left, so it is weaker. Most perforating decisions are a balance between open area and remaining strength.
Round vs square vs slotted holes
- Round holes — the most common and the strongest for a given size, especially on a staggered pitch. The default for filtration, screening and general use.
- Square holes — give higher open area and a clean screening edge; good where you want maximum flow or a particular look.
- Slotted holes — elongated openings for dewatering, sizing of elongated particles, or directional flow.
Pitch and staggering
Pitch is the centre-to-centre distance between holes. A staggered (60°) pitch packs holes more densely for higher open area and even strength, and is the usual choice for round holes. A straight (90°) pitch lines holes up in rows and columns — lower open area, but a regular look favoured for architectural and decorative work. Tighter pitch raises open area but removes metal between holes, so there's a practical minimum web for the sheet to stay sound.
Open area vs strength — the trade-off
Pushing open area up (bigger holes or tighter pitch) always costs strength and rigidity. If the sheet has a structural job — a walkway, a guard, a facade panel — you hold open area back and may step up the thickness. If the job is pure flow or filtration and the sheet is supported, you can run higher open area. Tell us the duty and we balance it.
Common patterns we stock
Standard round-hole staggered patterns cover most filtration, screening and guarding needs; square and slotted patterns are available for higher flow or sizing. Rather than memorise pattern codes, give us the hole size and open-area or flow you're after and we'll point you to a stock pattern.
How to specify
A complete perforated-sheet spec is:
- Hole size — diameter (round) or width (square/slot).
- Pitch — centre-to-centre, and staggered or straight.
- Sheet thickness.
- Material — SS, MS or GI.
- Sheet size and any margin or blank-border needs.
See the full perforated sheet range. Working in stainless and unsure of the grade? Read SS 304 vs 316 — which grade to use.