How do you calculate press brake tonnage?

Multiply 575 (the mild-steel air-bend constant) by thickness squared and the die-opening factor for tons per foot, then by bend length. With 0.0625 in², a 0.5 1/in die factor, a 1.0 tensile factor, and 4 ft: 575 × 0.0625 × 0.5 ≈ 18 tons/ft × 4 ft ≈ 72 tons.

What die opening should I use?

A common rule is a V-die roughly 8 times material thickness for air bending. A larger opening lowers the die-opening factor and required tonnage but increases the inside radius and springback, so it is always a trade-off.

Does tonnage go up with tensile strength?

Yes. Higher-strength material needs more force, which is why the tensile factor exists; stainless and high-strength steels can require 1.5 to 2 times the tonnage of mild steel for the same bend.

Air bending vs bottoming: how does tonnage differ?

Air bending needs the least force. Bottoming can need several times more, and coining more still, because you are forcing the material fully into the die. Multiply this air estimate up accordingly and confirm the tooling is rated for it.

Why does thickness get squared?

Bending force rises roughly with the square of thickness, so doubling thickness nearly quadruples the force. That is why the calculator takes thickness squared as an input rather than thickness itself.

Should I round the tonnage up or down?

Always up. Estimates ignore friction, die wear, and grain direction, and coining adds load, so leave headroom and never plan to run a press at its exact rated maximum.

Welding & Fabrication calculator

Press Brake Tonnage Calculator

Press brake tonnage is the forming force required to air-bend a given length of material to a target angle. Estimators and brake operators use it to pick a machine large enough to make the bend without stalling, and to avoid overloading tooling or the ram. Underestimate and the bend comes up short of angle; overestimate and you risk cracking dies or picking a machine you do not need. This calculator combines thickness, bend length, a tensile factor, and the die-opening term into a working tonnage figure you can check against your press rating.

What this calculator does

Estimate press brake tonnage required from material thickness squared, bend length, material tensile factor, and die opening factor.
Use it before scheduling a press brake job to confirm tonnage is within machine and tooling rating and the V-die opening is appropriate.
It multiplies material thickness squared, bend length, and a tensile factor into a load, then scales by the die-opening factor to estimate required tonnage.

Formula used

Tons per foot = 575 × thickness squared × die-opening factor × tensile factor (mild-steel air-bend rule)
Press brake tonnage estimate = tons per foot × bend length (round up for coining or bottoming)

Inputs explained

Material thickness squared:
Bend length:
Steel tensile-strength factor:
Die-opening factor (1/V):

How to use the result

Use it before setting up an air bend to confirm the press and tooling can produce the angle, and when comparing die openings to reduce required force.
It is an air-bending estimate; coining or bottoming can multiply the force several times over, and very small die openings drive tonnage and crack risk up sharply, so round up and stay within the die's rated capacity.

Current U.S. benchmarks

The producer price index for steel mill products stands at 374.203 (BLS, Jul 2026), up 22.5% from a year earlier. Quotes priced off last quarter's material cost miss this move.
Industrial electricity averages 8.71 cents per kWh across the U.S. (EIA, May 2026), up 5.1% from a year earlier. Energy-intensive steps carry this directly into unit cost.
U.S. iron and steel imports ran $2.2B in Jun 2026 (Census International Trade). The U.S. ran a trade deficit of $0.4B in the category that month. Import volumes are the pressure gauge behind tariff and reshoring decisions.
The U.S. has 53,790 fabricated metal products establishments employing about 1,441,471 workers (Census County Business Patterns, 2023).

Common questions

How do you calculate press brake tonnage? Multiply 575 (the mild-steel air-bend constant) by thickness squared and the die-opening factor for tons per foot, then by bend length. With 0.0625 in², a 0.5 1/in die factor, a 1.0 tensile factor, and 4 ft: 575 × 0.0625 × 0.5 ≈ 18 tons/ft × 4 ft ≈ 72 tons.
What die opening should I use? A common rule is a V-die roughly 8 times material thickness for air bending. A larger opening lowers the die-opening factor and required tonnage but increases the inside radius and springback, so it is always a trade-off.
Does tonnage go up with tensile strength? Yes. Higher-strength material needs more force, which is why the tensile factor exists; stainless and high-strength steels can require 1.5 to 2 times the tonnage of mild steel for the same bend.
Air bending vs bottoming: how does tonnage differ? Air bending needs the least force. Bottoming can need several times more, and coining more still, because you are forcing the material fully into the die. Multiply this air estimate up accordingly and confirm the tooling is rated for it.
Why does thickness get squared? Bending force rises roughly with the square of thickness, so doubling thickness nearly quadruples the force. That is why the calculator takes thickness squared as an input rather than thickness itself.

Last reviewed 2026-08-11.