Punching shears the material around the whole edge of the hole at once, so the force needed is the cut area (perimeter times thickness) multiplied by the material’s shear strength. The press or punch must have more capacity than this (a 20% margin is common), and stripping the punch back out takes extra force.
How to use the Punch Force Calculator
- Hole shape
- Diameter / side a
- Side b
- Cut perimeter
- Sheet thickness
- Material
- Custom shear strength
- Every result field is editable: type into Punch force and Sheet thickness plus every other field update to match.
Results update as you type, and every field accepts the units shown in its menu.
How it works
Choose the hole shape and enter its size, the sheet thickness and the material.
Inputs explained
| Field | What to enter |
|---|---|
| Hole shape | Choose one: Round, Square, Rectangle / slot, Custom perimeter |
| Diameter / side a | Units: mm, in, cm |
| Side b | Units: mm, in, cm |
| Cut perimeter | Units: mm, in, cm |
| Sheet thickness | Units: mm, in, cm |
| Material | Choose one: Aluminium 5052-H32 (≈ 20 ksi), Aluminium 6061-T6 (≈ 30 ksi), Copper (≈ 25 ksi), Brass (≈ 35 ksi) … |
| Custom shear strength | Units: MPa, psi, ksi, kPa, Pa |
Example values
How the main result changes when Sheet thickness changes and everything else stays at the example values above:
| Sheet thickness (mm) | Punch force (kN) |
|---|---|
| 1.5 | 32.52 |
| 2.25 | 48.77 |
| 3 | 65.03 |
| 3.75 | 81.29 |
| 4.5 | 97.55 |
| 6 | 130.06 |
Formula
F = perimeter × thickness × shear strength
Round: perimeter = π D; square: 4a; rectangle: 2(a + b)
Worked example
Inputs: Hole shape: Round; Diameter / side a: 20 mm; Sheet thickness: 3 mm; Material: Mild steel (≈ 50 ksi).
Results: Cut perimeter = 62.83 mm; Punch force = 65.03 kN; Press capacity with 20% margin = 78.04 kN.
Frequently asked questions
How do I calculate punching tonnage?
Perimeter (in) × thickness (in) × shear strength (tons/in²). For mild steel use about 25 US tons per in².
What is the shear strength of mild steel?
About 50,000 psi (345 MPa), roughly 75–80% of its tensile strength.
How can I reduce punch force?
Use shear-angled punches, stagger multiple punches or punch in stages.