Perforated sheet guide
Perforated sheet guide: open area and weight calculator
Work out the open area and weight of a hole pattern, see which patterns we keep in stock, and read up on what the codes mean.
R5 T8
5mm round holes on an 8mm staggered pitch. The bar between holes is 3mm.
Closest patterns we have
Bold = in stock. Other materials made to order, usually 5 to 7 days.
How to read a pattern code
- R
- Round hole. C means a square hole.
- 5
- Hole size in millimetres. For a square hole, the length of one side.
- T
- Staggered pitch, holes at 60°. U means in-line, holes in straight rows.
- 8
- Pitch: the distance from the centre of one hole to the centre of the next, in millimetres.
So R5 T8 is 5mm round holes on an 8mm staggered pitch, about 35% open. You’ll also see it written 5mm R5, R5T8, or “5mm hole, 8mm pitch”.
Staggered or in-line
For the same hole and pitch, staggered gives more open area than in-line, because the rows nest together.
Open area
Open area is the share of the sheet that’s hole. A bigger hole or a tighter pitch means more open area and less metal between the holes. The bar between two holes is the pitch minus the hole, so an R5 T8 has a 3mm bar.
The calculator uses the standard formulas:
| Round, staggered (T) | 90.7 × (hole ÷ pitch)² |
|---|---|
| Round, in-line (U) | 78.5 × (hole ÷ pitch)² |
| Square, in-line (U) | 100 × (hole ÷ pitch)² |
The figures on our product pages are worked out the same way, so they’ll match.
Hole size and sheet thickness
As a rough guide, the hole should be at least as big as the sheet is thick: a 3mm hole in 3mm sheet, but not in 5mm. Smaller holes in thicker sheet can sometimes be done, so ring us if that’s what you need.
Sheet sizes
Stock sheets are 2000 x 1000mm and 2500 x 1250mm. We can get 3000 x 1500mm in, usually in 5 to 7 days. We cut part sheets and exact sizes from any of them.
Questions we get asked
What does 15mm pitch mean?
The holes are 15mm apart, measured from the centre of one hole to the centre of the next. It doesn’t tell you the hole size, so a 15mm pitch could be R10 T15 (10mm holes, about 40% open) or R8 T15 (8mm holes, about 26% open).
What are R and T values on perforated sheet?
R is the round hole size in millimetres and T is the staggered pitch, the centre-to-centre distance between holes. R5 T8 is a 5mm hole on an 8mm pitch.
What’s the difference between T and U?
T is a staggered pattern, with every other row shifted by half a pitch. U is in-line, with the holes in straight rows and columns.
How do I work out open area?
For round holes on a staggered pitch, divide the hole size by the pitch, square it and multiply by 90.7. R5 T8 is 5 ÷ 8 = 0.625, squared is 0.39, times 90.7 is about 35%. The calculator at the top of this page does it for you.
How much does perforated sheet weigh?
Take the weight of plain sheet and knock off the open area. Mild steel weighs 7.85 kg per m² for every millimetre of thickness, so 1.5mm plain sheet is 11.78 kg/m². R5 T8 is 35% open, so the same sheet perforated R5 T8 is 11.78 × 0.65 = 7.60 kg/m². Pick your material and thickness in the calculator to get the figure per m² and per sheet.
Can you make a pattern that isn’t listed?
Often, yes. Tell us the hole, pitch, material and thickness and we’ll check whether it can be made, usually within 5 to 7 days.
Know what you need?
Send us the pattern, material, thickness and sizes and we’ll come back with a price, usually the same working day.