Punching Force Calculator: Perimeter, kN & Tonnage
Calculate ideal cutting force for simultaneous punching through sheet. Use the total edge length engaged in cutting and the material’s shear strength.
Calculate and check
Default values are examples. Replace them with verified inputs for your job. Changing a unit or mode does not convert existing inputs.
Formula and perimeter selection
Ideal force F = perimeter × thickness × shear strength. With mm, mm and MPa (N/mm²), the result is newtons. Divide by 1000 for kN, 9806.65 for metric tonne-force, or 8896.44323 for US short ton-force. These are force units; a metric tonne of mass is not itself a force.
For a round hole, perimeter is πd. A rectangular hole uses 2(length + width). If several punches cut simultaneously, add their cutting perimeters. Do not use the area removed in place of perimeter. The default shear strength is a hypothetical example, not a universal steel property.
Worked example: one 20 mm round hole
A 20 mm hole has a cutting perimeter of 62.83185 mm. With 2 mm stock and 300 MPa shear strength, F = 37,699.11 N = 37.6991 kN. This is approximately 3.8443 metric tonne-force or 4.2375 US short ton-force. Four identical simultaneous holes multiply that ideal cutting force by four.
Changing thickness from 2 to 3 mm increases this ideal model by 50%, if material shear strength and the engaged perimeter remain unchanged.
A press-selection check needs more information
This equation does not include stripping force, dull-tool effects, die clearance, uneven engagement, punch shear geometry or dynamic loading. It also does not establish press energy, off-center load capacity, turret or tooling capacity, or available tonnage at the operating stroke position.
Obtain shear strength and recommended tooling clearance from appropriate material and tooling data. Check every relevant machine and tool limit with the manufacturer; do not simply select a press equal to this ideal force. For bending rather than shearing, use the separate press-brake tonnage tool because its load model is different.
How to count the cutting edge for a mixed-hole hit
Count every edge cutting through the sheet at the same instant. A round hole contributes πd; a rectangular hole contributes 2(a+b). The blank area removed is not the cutting perimeter. If tooling staggers punch engagement, do not assume every edge reaches its maximum load simultaneously; use the actual tooling design.
One round hole plus one rectangular hole
For the illustrated holes punched simultaneously, enter perimeter 142.8319 mm, thickness 2 mm and an illustrative shear strength of 300 MPa. Ideal force is 142.8319 × 2 × 300 = 85,699.1 N, or 85.6991 kN. The 300 MPa value is an arithmetic assumption, not a specification for an unnamed steel grade.
Ask the material or tooling supplier for the shear-strength value applicable to the supplied grade and condition. Do not silently substitute tensile strength: the quantity required here is shear strength. Keep its source with the calculation, together with the drawing revision and simultaneous punch count.
Next check actual sheet thickness and hole acceptance dimensions. Force alone does not establish stripping load, press energy or tool capacity. Reference: Mate: calculating punching force.
Content updated October 8, 2026. Sources and numerical examples are explained above; examples are not production test results. Editorial method · Report a correction.
References and verification
Original explanations and worked examples by MfgWorkbench. Sources below support the stated concepts or selected reference data; they do not certify every example or a production application.
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