Press brake tonnage calculator
Four numbers decide the tonnage: what the material is, how thick it is, how long the bend is, and how wide the V-opening is. Enter them and this gives you the planning figure — plus the margin to buy against.
Planning figure only, from the standard air-bending relationship575 × t² ÷ V, which gives tons per foot of bend — multiply by your bend length in feet. Real force moves with alloy temper, tooling condition, ram speed and how true your V-opening is. Confirm against your tooling maker's chart before committing to a machine.
What the numbers mean
Thickness does most of the work. It appears squared in the formula, so doubling the steel from 1/8" to 1/4" roughly quadruples the force for the same bend. This is the single most common reason a buyer ends up with an undersized machine: they sized for the material they use most often, then took one job in heavier plate.
The V-opening works the other way — a wider V needs less force but produces a larger inside radius. The 8 × thickness rule is the usual starting point, and it is a starting point rather than a law. Go below it and you risk the material cracking at the bend; go well above it and the part springs back more than you want.
The method multiplier is the part people skip. Air bending lets the material find its own angle, so the punch only touches at two points. Bottoming presses the material into the die to set the angle, and coining forces it fully into the shape — both need substantially more tonnage for the same part. If your work involves a lot of bottoming or coining, sizing the machine on an air-bend figure will leave you short.
Undersized versus oversized
Too little tonnage shows up as an inability to reach the angle, inconsistent results between hits, and — over time — damage to tooling and to the machine's bed and ram. Too much tonnage costs you money three times over: a higher purchase price, a heavier machine, and worse results on thin material, where excess force magnifies every small variation in the sheet.
The 20% margin on the result above is a planning allowance, not a precision figure. It covers the difference between the steel you tested on and the coil you actually bought.
Send these four numbers to us
Thickness, bend length, V-opening and the material. We will come back with a machine configuration, the tooling to go with it, and a quote.