Calculator
Press Brake Tonnage Calculator
Air-bend force per foot and for the whole bend, plus the inside radius and shortest flange to expect. Built on the standard 575 × t² ÷ V rule.
Press brake tonnage chart (mild steel)
Air-bend force for mild steel at the suggested die opening for each thickness. For other metals, multiply by 1.1 for A572 Grade 50, 1.5 for 304 stainless or 0.5 for 5052 aluminum.
| Thickness | Decimal (in.) | Die opening (in.) | Tons/ft | 10 ft bend (tons) | Inside radius (in.) |
|---|---|---|---|---|---|
| 16 ga | 0.0598 | 1/2 | 4.1 | 41 | 0.080 |
| 14 ga | 0.0747 | 5/8 | 5.1 | 51 | 0.100 |
| 12 ga | 0.1046 | 7/8 | 7.2 | 72 | 0.140 |
| 10 ga | 0.1345 | 1-1/4 | 8.3 | 83 | 0.200 |
| 3/16 | 0.1875 | 1-1/2 | 13.5 | 135 | 0.240 |
| 1/4 | 0.2500 | 2 | 18.0 | 180 | 0.320 |
| 5/16 | 0.3125 | 2-1/2 | 22.5 | 225 | 0.400 |
| 3/8 | 0.3750 | 3 | 27.0 | 270 | 0.480 |
| 1/2 | 0.5000 | 4 | 35.9 | 359 | 0.640 |
| 5/8 | 0.6250 | 7 | 32.1 | 321 | 1.120 |
| 3/4 | 0.7500 | 8 | 40.4 | 404 | 1.280 |
| 1 | 1.0000 | 10 | 57.5 | 575 | 1.600 |
How the force is figured
tons/ft = 575 × t² ÷ V × material factor
total tons = tons/ft × bend length (ft)
inside radius ≈ 0.16 × V (mild steel, air bending)
The 575 constant is for mild steel with about 60,000 psi tensile strength bent to 90° in a V die; t is the thickness and V the die opening, both in inches. Stronger material, a narrower die or a longer bend all raise the force. Bottoming and coining, where the punch presses the part into the die, take several times the air-bend figure.
Questions
How do you calculate press brake tonnage?
For air bending mild steel to 90°, tons per foot = 575 × thickness² ÷ die opening, all in inches. Multiply by the bend length in feet, and by a material factor for stronger or softer metals. Example: ¼ in. mild steel over a 2 in. die takes about 18 tons per foot, so a 10 ft bend needs about 180 tons.
What die opening should I use?
A common starting point is 8 × the thickness up to ½ in., then 10 to 12 × the thickness for heavier plate. A wider die lowers the force but leaves a larger inside radius and needs a longer flange.
What inside radius will an air bend give me?
In air bending the radius forms at a share of the die opening: roughly 16% of the opening for mild steel, about 21% for 304 stainless and about 14% for 5052 aluminum. Bottoming and coining set tighter radii but take several times the force.
How long and how thick can you bend?
Our CNC press brakes bend parts up to 26 ft long and up to 1 in. thick, depending on bend length and grade. Send the drawing and we will confirm the tooling and setup.
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We take DXF, DWG and STEP files, dimensioned PDFs and bills of material. Our estimating team reviews every request and comes back with an itemized quote.
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