Calculating Press Brake Bending Tonnage: A Practical Guide

Bend force determines whether your press brake — and your tooling — can make a given part. Estimating it correctly protects both your machine and your dies.

The Core Variables

Air-bend force rises with material tensile strength and thickness squared, and falls as the V-opening widens. A common practical formula is:

Force per metre ≈ (575 × T² × tensile factor) ÷ V, where T is thickness (mm) and V is the die opening (mm).

Worked Example

For 2 mm mild steel in a 16 mm V-die, the required force is on the order of 15–18 tons per metre of bend length. A 1-metre bend therefore needs roughly 18 tons of machine capacity — well within a small press brake.

Don't Forget

• Bottoming multiplies force several times over air bending; coining can multiply it 5–30×.
• Stainless steel needs ~1.5× the force of mild steel; high-strength grades more still.
• Always check the tool load rating (t/m) — never exceed the die's maximum load.

When in doubt, use a tonnage chart or your control's built-in calculator, and widen the V-opening to bring force down.