Press Brake Tonnage Calculator
Underestimate Tonnage and the Brake Simply Won't Bend It
A press brake needs enough force to overcome a material's resistance to bending, and that force requirement doesn't scale gently — it climbs with the square of material thickness. A rough tonnage estimate before a job goes a long way toward avoiding a brake that stalls mid-bend or, worse, tooling that gets overloaded trying to force it.
The Formula
This is an industry rule-of-thumb estimate built around a die opening roughly 8 times material thickness, using a material factor that varies by metal type. It's meant for planning purposes — always confirm against your press brake manufacturer's official tonnage chart before running a job.
Worked Examples
| Material | Length | Thickness | Die Opening | Estimated Tonnage |
|---|---|---|---|---|
| Mild Steel | 48 in (4.0 ft) | 0.125 in | 1 in | 31.25 tons |
| Stainless Steel | 48 in (4.0 ft) | 0.125 in | 1 in | 40.62 tons |
Same length, same thickness, same die opening — stainless steel alone requires roughly 30% more tonnage than mild steel to bend, reflecting its higher material factor in this estimate.
Where This Calculation Matters
- Job planning — confirming a shop's available press brake has sufficient rated tonnage before scheduling a bending job.
- Tooling selection — choosing an appropriate die opening, since a narrower die increases required tonnage for the same bend.
- Quoting and machine selection — deciding whether a job needs to be routed to a larger-capacity brake elsewhere in a shop.
How to Use This Calculator
- Enter Bend Length (in), Material Thickness (in), and Die Opening (in).
- Select the material: Mild Steel, Stainless Steel, Aluminum, or Galvanized Steel.
- Select Calculate to get the estimated tonnage required.
Related Calculations
Before setting up the bend, calculate the flat pattern length needed with the Bend Allowance Calculator.