By Zencalcy Editorial TeamLast reviewed About us
Punching shears the metal around the hole's perimeter, so force is perimeter × thickness × shear strength. A 1-inch hole in 1/8-inch mild steel needs about 9 tons, which is why press capacity and tool strength matter more than the hole size suggests.
Tonnage needed to punch a hole in sheet metal.
F = perimeter × thickness × shear strength
Shear strength is about 0.6–0.8 of tensile strength: mild steel 40,000 psi, stainless 55,000, aluminium 20,000. Add 20–30% for stripping force, tool wear and shock loading when choosing a press.
| Symbol | Meaning |
|---|---|
| P | Hole perimeter. |
| t | Material thickness. |
| τ | Shear strength. |
Perimeter 3.14 in × 0.125 × 40,000 = 15,700 lb, or 7.9 tons.
Continue with the Beam Deflection Calculator, Beam Load Calculator, Bending Stress Calculator, or the Wood Beam Span Calculator — or browse more structural & workshop and all construction calculators.
Calculated force plus 20–30%. A 10-ton press is marginal for a 1-inch hole in 1/8-inch steel; a 15-ton press is comfortable.
Results use standard construction estimating arithmetic: volumes from measured area and depth, unit weights from published material densities, and code-referenced spans or clearances where the page names a code. Quantities are rounded up to whole saleable units and include the stated waste allowance. These tools are planning aids, not structural design, and do not replace a licensed engineer, a local code check, or a contractor's site measurement.
Reference material used to build and check this calculator:
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Content updated: September 2026