All dimensions below are in millimeters (mm).
For catalog materials, this value is suggested from material family and stock thickness (when thickness is a positive number). Choose "Custom" above to keep a manual clearance %.
Punch force uses catalog yield strength (σy, MPa) with τ ≈ σy/√3 for shear. Approximate planning only—not press tonnage certification.
Results
Enter positive thickness, clearance % between 0 and 50, and valid hole dimensions to see results.
More Information
What is punch and die clearance?
In sheet punching and stamping, clearance is the gap between the punch (male cutter) and the die opening (female). It is usually stated as radial clearance per side: one-half of the diameter clearance on a round punch pair. Enough clearance lets the fracture shear cleanly through the sheet and avoids galling or tight stripping; too little increases punch wear and punch breakage risk.
How this calculator works
This tool scales clearance from stock thickness and your nominal clearance percentage:
where c = radial clearance per side (mm), p = clearance as % of thickness per side, and t = stock thickness (mm).
Approximate die opening sizes add twice that radial amount across each characteristic dimension (total 2c across a diameter or span):
- Round: die diameter ≈ nominal hole diameter + 2c
- Square / rectangle / stadium: each listed span (side, width, length, etc.) increases by 2c in this simplified symmetric model
Punch force estimate
The results panel can approximate blanking/punching force using the shear line length of the nominal punch outline (same as your hole dimensions), stock thickness t, and a shear stress from the material's catalog yield strength. This implementation uses τ ≈ σ_y / √3 (von Mises shear yield) and:
Perimeter rules: round πD; square 4S; rectangle 2(W+H); stadium πW + 2(L−W) with overall length L and narrow width W.
Real press loads include friction, die geometry, and shear versus fracture behavior—use vendor data for tonnage requirements.
Choosing clearance %
Typical published values depend on material, hardness, and thickness bands from tooling suppliers—not a single universal number. Start from handbook or vendor tables for your alloy and operation, then use this calculator to turn your chosen % into absolute clearance (mm) for quick sizing checks.
Limitations
- Outputs are approximations for discussion and early tooling layout—not a substitute for qualified die design.
- Burr height, edge quality, and stripping behavior depend on punch–die alignment, sharpness, and lubrication.
- For precision work or unfamiliar materials, confirm clearance with your press shop or supplier recommendations.