Where do this calculator's numbers come from?

From the PG SRL technical table: tonnage per metre tabulated for every thickness × die pair, on S235 steel with UTS ≈ 420 N/mm², with the material coefficients of the ESA database on our press brakes (1.0 S235 · 1.57 stainless · 0.59 aluminium 5754). It's the same table our configurator uses.

Why don't you use the handbook formula?

We use it as the reference physics (F ∝ UTS·S²/V), but the literature constant underestimates by about 15% the real shop-floor force. The table incorporates friction, tolerances and real materials.

Does the result hold for coining too?

Selecting Coining applies an indicative ×4.5 factor, in line with industry calculators. Literature ranges from 3 to 10 times the air-bending force depending on geometry and material: for serious coining sizing, contact us.

It's the folded edge of architectural sheet metal: an air pre-bend at ~30° followed by flattening the leg toward the sheet. Used for stiffened edges and joints. The calculator applies a ×1.9 factor up to 2 mm and ×3 on thicker gauges. The base is the air bend with the recommended die; for a fully closed hem use coining as the force reference.

How do I choose between the recommended V and the others?

The recommended V (≈8×S in the 1-12 mm range) is the right starting point in 90% of cases. A different V makes sense when the flange is short (narrower V) or you want lower force and no die marks (wider V).

What is the target bend angle for?

It sets the overbend: the angle to set on the machine to compensate springback and reach the angle you want. Force, die, radius and flange stay referenced to the 90° air bend of the PG table, so they don't change with the angle. Coining nearly eliminates springback.

How accurate is the springback figure?

It's a typical range per material family. The real value depends on batch, rolling direction and R/S ratio: the numerical controls on our press brakes compensate it automatically with angle correction.

Does the calculation tell me which press brake to buy?

It gives you minimum tonnage and length. The machine for this bend box suggests the smallest PG press brake that handles the force and length of your bend; with less than a 15% margin on the rated force the next size up is the better choice, and the box tells you so. From there you move to the configurator, where sector, volumes and accessories complete the sizing.

Press brake tonnage calculator · Metric

Your bend

Material k 1.00

Thickness S mm

V-die opening mm

PG technical table — the same used by the configurator

Bend length L mm

Target bend angle degrees

Bending type

01 — The engineA real table, not a textbook formula.

This calculator doesn't run a generic formula: it runs the PG SRL technical table — the same one working inside our configurator — with the tonnage per linear metre already tabulated for every thickness × V-die pair, on reference S235 steel (UTS ≈ 420 N/mm², the same basis as the tooling makers’ tables). The calculation is:

F [t] = t/m (table, for S and V) × L [m] × k (material)

t/m is the specific force of the die opening: shop-floor experience turned into numbers, not handbook constants.
L is the bend length in metres. A 2.5 m bend counts as 2.5.
k is the material coefficient, i.e. its strength relative to S235 in the material database of the ESA CNC on PG press brakes: 1.0 S235 steel, 1.35 S355, 1.57 stainless 304/316, 0.59 aluminium 5754. A real batch can differ by a few per cent.

The physics underneath is still the handbook one — force grows with thickness squared and drops with die width (F ∝ UTS·S²/V) — but the pure textbook formula, with its literature constant, underestimates by about 15% the force we actually measure on the shop floor: friction, tooling tolerances and real materials don't live in book constants. That's why we trust the table.

02 — The V-dieThe real rules for choosing it.

The rule the table applies (and that you'll find preselected in the calculator):

Thickness	Recommended V	Why
under 1 mm	10 – 13 × S	minimum die sizes exist (V6, V8): the ratio goes up by necessity
1 – 12 mm	≈ 8 × S	the right compromise between force, radius and flange
15 mm and up	≈ 10 × S	heavy plate: wider to contain force and cracking

In the calculator you can also pick the other dies available for your thickness: a V narrower than recommended marks the part and raises the force, a wider one lowers it but enlarges inner radius and minimum flange — if your part has a short flange, the wide V won't fit it.

03 — Radius and flangeThe two geometric consequences of the V.

In air bending the inner radius is not set by the punch: it's set by the die opening. In the table the inner radius ≈ V/6, about 16% of the die opening, and the minimum flange B ≈ 0.7 × V — the shortest leg the die can grip: shorter bends need dedicated tooling (narrow blades, 88° tools). How to read the full chart, material by material: bending chart by material.

04 — SpringbackWhy you always bend "a little further".

When the force is released, the sheet elastically recovers part of the deformation: that's springback. It grows with the material's yield-to-modulus ratio and with the radius-to-thickness ratio — which is why stainless and high-strength steels "come back" more than mild steel. On the shop floor it's compensated by overbending. The typical ranges shown by the calculator:

Material	Typical overbend
Mild steel (S235–S275)	0.5 – 1.5°
Austenitic stainless (304/316)	1 – 3°
Aluminium	1.5 – 3°
High-strength steels (S700+)	3 – 6°

The numerical controls on our press brakes compensate springback in the machine with automatic angle correction — the ranges above help you understand the phenomenon, they don't replace the correction.

05 — LimitsWhat this tool does not tell you.

Acute angles (≤60°): force grows beyond the table — case-by-case evaluation.
Coining: the calculator applies an indicative ×4.5 factor, but literature ranges from 3× to 10× depending on geometry and material.
Hemming: the folded edge is formed in two stages (air pre-bend at ~26-35° with a sharp punch, then flattening of the leg outside the die). The factor on the air bend is ×1.9 up to 2 mm and ×3 above, aligned with tooling makers' benchmarks. Typical of fine architectural sheet metal: 0.6-1.5 mm, 3 mm max. For a fully closed hem (double thickness) the force reference is coining.
Coatings (galvanised, pre-painted): +5-10% apparent strength.
Bends longer than the machine: that's a tandem configuration.

Technical note. Results are first-sizing estimates based on the PG technical table and average material coefficients: they don't replace engineering verification on your drawing and samples. Real forces, radii and springback depend on material batch, rolling direction, tooling condition and part geometry. For final machine sizing contact our engineering department.

The numbers in this calculator are the ones we size our own machines with. For medium and heavy fabrication and long bends the answer is the hydraulic press brake DCA, from 40 to 3,000 t and up to 16.2 m. Up to 200 t and 4.2 m, on thin sheet, there is the electric press brake E.DCA; in between, the hybrid press brake H.DCA, from 65 to 320 t. Beyond 16 m or 3,000 t two or more machines work as a tandem press brake, up to 6,000 t. All of them are CNC press brakes built to order.

Next step

You have the parameters. Now the machine.

From the "machine for this bend" box the configurator opens with the suggested machine’s force and length and your sheet thickness already set: in 7 steps you get a press brake sized on your actual work, with a quotation. Or write to us with two lines about the part you bend: we reply within 24 hours.

Configure your machine →

Bending parameters. All of them, in real time.