Press Brake Tonnage Calculator
Air-bending tonnage per metre is 1.33 × tensile strength × t² ÷ V, and with the common V = 8 × t die opening that simplifies to 0.166 × tensile × t. Enter thickness, material and bend length to get the force in kilonewtons and metric tons, plus a 20% margin for the press size. It is an estimate for air bending — bottoming and coining run significantly higher.
Press size with 20% margin: ≈ 135.7 kN
Air bending with a V-die opening of 8 × t. Bottoming runs roughly 3–5× higher; coining higher still. This is an estimate for press selection, not a machine setting — the die shoulder radius and grain direction both move the real number.
Questions about bending tonnage
P (kN/m) = 1.33 × σb × t² ÷ V with V = 8t, tensile strengths from the mill data for the grades we fabricate.
Why is the V-die opening 8 × t?
It is the common air-bending rule: a die opening near eight thicknesses keeps the tonnage sane and the inside radius close to one thickness on most gauges. If your tooling runs a different V, the tonnage scales inversely — half the opening roughly doubles the force. For production we quote with the die we will actually load.
Does the calculator include springback?
No — tonnage and springback are separate problems. The force bends the metal; springback is the elastic recovery after the force releases, and it is compensated with overbend or tooling, not with more tonnage. High-strength alloys spring back more per the same radius.
What about bottoming or coining?
Both push the material into the die, so the force climbs steeply — bottoming runs roughly three to five times the air-bending figure, and coining higher still. The calculator is deliberately air-bending only, because that is how most of the work in this shop runs.
Keep going
Calculators — enter dimensions, get a number
Sheet Metal Weight CalculatorWeight per piece and per batch from L × W × t, with real alloy densities.Bend Allowance CalculatorThe neutral-axis length through a bend, from thickness, radius, angle and K-factor.Sheet Metal Cost CalculatorWhere a part’s cost actually sits — material, cutting, forming, finishing and setup.K-Factor Calculator (Reverse)Reverse a K-factor from a real bend: outside dimensions and flat length in, K out.Hole-to-Bend Distance CalculatorMinimum hole-to-bend and hole-to-edge clearances from thickness and inside radius.Charts and checklists — read, print, work through
Sheet Metal Gauge to mm ChartSteel (MSG) and aluminium (B&S) gauge dimensions, and why we quote in mm.Sheet Metal DFM ChecklistThe 24 checks we run on a drawing before we quote it, grouped and explained.Sheet Metal RFQ ChecklistThe 12 items that make an RFQ quotable in one round, with the reason each matters.Sheet Metal Supplier Audit Checklist13 remote-verifiable checks for a sheet metal supplier, in four passes.Send the part — we programme the real die
Tonnage estimates keep a press from stalling; a quotation from WERIX comes with the tooling, tonnage and angle compensation for the actual die that will run your bends.
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