Technical resources
Understanding perforation: formulas and characteristics
For an instant calculation, use the calculator
Notation
Open area
| Layout | Formula |
|---|---|
| U — straight line, square pitch | OA = 78.54 × (d / p)² |
| T — 60° staggered | OA = 90.69 × (d / p)² |
| M — 45° staggered | OA = 157.08 × (d / p)² |
| Z — staggered on a p1 × p2 rectangle | OA = 157.08 × d² / (p1 × p2) |
| Layout | Formula |
|---|---|
| U — straight line | OA = 100 × (a / p)² |
| T — 60° staggered | OA = 115.47 × (a / p)² |
Example: an R 5 T 7 pattern (5 mm round, 60° staggered, 7 mm pitch) gives 90.69 × (5/7)² = 46.3% open area.
Hole density
| Layout | Formula |
|---|---|
| U — straight line | n = 10,000 / p² |
| T — 60° staggered | n = 11,547 / p² |
| M — 45° staggered | n = 20,000 / p² |
Example: 7 mm pitch in T layout → 11,547 / 49 = 236 holes per dm².
Weight
Weight (kg/m²) = e × ρ × (1 − OA / 100)
with e in mm and ρ in kg/dm³.
Example: a 2 mm steel sheet with 46.3% open area weighs 2 × 7.85 × 0.537 = 8.43 kg/m² instead of 15.7 kg/m² solid.
| Material | ρ (kg/dm³) |
|---|---|
| Steel | 7.85 |
| Stainless steel 304 / 316 | 7.90 / 8.00 |
| Aluminium | 2.70 |
| Copper | 8.90 |
| Brass | 8.50 |
Quick reference
Round holes in T layout: diameter d in rows, pitch p in columns (mm). Values in % calculated with the formula above, rounded to the nearest whole number (to one decimal place below 10%); the highlighted cell corresponds to the R 5 T 7 pattern.
| d \ p | 2 | 3 | 4 | 5 | 6 | 7 | 8 | 10 | 12 | 15 | 20 |
|---|---|---|---|---|---|---|---|---|---|---|---|
| 1 | 23 | 10 | 5.7 | 3.6 | 2.5 | 1.9 | 1.4 | 0.9 | 0.6 | 0.4 | 0.2 |
| 1.5 | 51 | 23 | 13 | 8.2 | 5.7 | 4.2 | 3.2 | 2.0 | 1.4 | 0.9 | 0.5 |
| 2 | — | 40 | 23 | 15 | 10 | 7.4 | 5.7 | 3.6 | 2.5 | 1.6 | 0.9 |
| 2.5 | — | 63 | 35 | 23 | 16 | 12 | 8.9 | 5.7 | 3.9 | 2.5 | 1.4 |
| 3 | — | — | 51 | 33 | 23 | 17 | 13 | 8.2 | 5.7 | 3.6 | 2.0 |
| 4 | — | — | — | 58 | 40 | 30 | 23 | 15 | 10 | 6.4 | 3.6 |
| 5 | — | — | — | — | 63 | 46 | 35 | 23 | 16 | 10 | 5.7 |
| 6 | — | — | — | — | — | 67 | 51 | 33 | 23 | 15 | 8.2 |
| 8 | — | — | — | — | — | — | — | 58 | 40 | 26 | 15 |
| 10 | — | — | — | — | — | — | — | — | 63 | 40 | 23 |
A formula ignores feasibility. The diameter / thickness ratio, the type of material, the width of the margins, idle strokes and behaviour when bent cannot be calculated: they are a matter of judgement. That is our job.
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