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.
Tips for an accurate estimate
- Keep units consistent – the calculator handles conversions, but check every field’s unit before reading a result.
- Use values from standards, data sheets or test pieces whenever you have them; typical values are only a starting point.
- Apply appropriate safety factors and have structural, electrical and pressure work checked by a qualified professional.
- Record the inputs you used so the calculation can be reviewed later.
Common mistakes to avoid
- Confusing diameter and radius, or nominal and actual sizes.
- Using allowable stresses and ultimate strengths interchangeably.
- Treating rule-of-thumb results as a substitute for code tables or an engineered design.
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 strengthRound: perimeter = π D; square: 4a; rectangle: 2(a + b)Worked example
Inputs — Hole shape: Round; Diameter / side a: 20 mm; Side b: 30 mm; Cut perimeter: 100 mm; Sheet thickness: 3 mm; Material: Mild steel (≈ 50 ksi); Custom shear strength: 300 MPa.
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.
What formula does the Punch Force Calculator use?
F = perimeter × thickness × shear strength.