KRRASS sheet metal machinery factory in Nanjing

Press Brake Tonnage Calculator

Estimate the bending force for your material, thickness, bend length and V-die opening. Use metric or inch dimensions, compare bending methods, and find the tonnage you need to start selecting a KRRASS press brake.

Bending Force & Machine Selection

Calculate Bending Force

Enter material, sheet dimensions and the actual V-die opening to estimate force and plan your press brake capacity.

Enter your values

Material

Sheet thickness (S) mm Bend length (L) mm

V-die opening (V)

V presets are 6 × S, 8 × S and 10 × S. They are starting points for air bending; use Custom to match the actual tooling and verify its load rating.

Bending method

Air bending estimate. Confirm material strength and the actual V-die opening, then check machine and tooling load ratings.

Press brake air bending diagram showing force, sheet thickness, inside radius, flange length and V-die opening — Air bending geometry: bending force, sheet thickness S, inside radius Ri, minimum flange B and V-die opening V.

Bending Force Formula

KRRASS air-bending baseline for mild steel at 450 MPa:

P = 650 × S² × L / VP in kN · S and V in mm · L in meters

P: Bending force (kN)
S: sheet thickness (mm)
L: Bend length (meters)
V: V-die opening width (mm)

For other materials, multiply P by UTS / 450. UTS is tensile strength in MPa. Divide kN by 9.80665 for metric tons.

Bottoming: 3–5× air-bending force. Coining: 5–10×. These are preliminary ranges; verify actual material, process load and tooling capacity before machine selection.

Quick start

How To Use The Calculator

Follow four steps to estimate bending force, then review the worked example using the calculator's default sheet and tooling values.

1Choose the closest material grade. The displayed tensile strength sets the force correction relative to 450 MPa mild steel.
2Enter sheet thickness and bend length. Switch to inch when your drawing is imperial; all results remain clearly labelled.
3Choose the die opening: minimum, optimal, maximum, or a custom V value that matches your tooling.
4Select the bending method. For air bending, add a 20–25% initial sizing margin and check working length and tooling ratings. For bottoming or coining, have the actual process load and tooling verified before selecting a machine.

Worked Example

Air bend a 4,000 mm long, 6 mm carbon steel sheet (450 MPa) on a 48 mm V-die.

P = 650 × 6² × 4 / 48 = 1,950 kN (L = 4,000 mm = 4 m)
1,950 kN ÷ 9.80665 ≈ 198.8 t (219.2 US tons)
Inside radius ≈ 0.16 × 48 = 7.7 mm; minimum flange ≈ 0.78 × 48 = 37.4 mm
With a 25% margin, plan for at least 248.6 t of capacity, then verify the tool rating and working length.

Air bending · tons per meter

Press Brake Tonnage Chart

Air-bending metric tons per meter on the listed optimal V-die: mild steel 450 MPa, stainless 304 650 MPa and aluminum 5052-H32 240 MPa. Multiply by bend length in meters for total force.

Air-bending tonnage per meter for mild steel, stainless 304 and aluminum 5052-H32
Thickness S (mm)	Min. V (mm)	Optimal V (mm)	Max. V (mm)	Mild steel radius (mm)	Min. flange (mm)	Mild steel 450 MPa (T/m)	Stainless 304 (T/m)	Aluminum 5052 (T/m)
0.5	3	4	5	0.6	3.1	4.1	6.0	2.2
1	6	8	10	1.3	6.2	8.3	12.0	4.4
1.2	7.2	9.6	12	1.5	7.5	9.9	14.4	5.3
1.5	9	12	15	1.9	9.4	12.4	18.0	6.6
2	12	16	20	2.6	12.5	16.6	23.9	8.8
2.5	15	20	25	3.2	15.6	20.7	29.9	11.0
3	18	24	30	3.8	18.7	24.9	35.9	13.3
4	24	32	40	5.1	25.0	33.1	47.9	17.7
5	30	40	50	6.4	31.2	41.4	59.8	22.1
6	36	48	60	7.7	37.4	49.7	71.8	26.5
8	48	64	80	10.2	49.9	66.3	95.7	35.4
10	60	80	100	12.8	62.4	82.9	119.7	44.2
12	72	96	120	15.4	74.9	99.4	143.6	53.0
14	84	112	140	17.9	87.4	116.0	167.5	61.9
15	90	120	150	19.2	93.6	124.3	179.5	66.3
16	96	128	160	20.5	99.8	132.6	191.5	70.7
18	108	144	180	23.0	112.3	149.1	215.4	79.5
20	120	160	200	25.6	124.8	165.7	239.4	88.4
22	132	176	220	28.2	137.3	182.3	263.3	97.2
25	150	200	250	32.0	156.0	207.1	299.2	110.5

Material reference

Material Strength Guide

Compare representative tensile strengths and force factors, ordered from low to high. Actual strength depends on grade, temper and thickness; confirm the material certificate before production.

Material strength and bending force factor table
Material	Example UTS (MPa)	Force vs. mild steel	Estimated air-bend radius
Soft aluminum / aluminium / copper sheet — annealed, soft-temper non-ferrous sheet	100	0.22×	0.14 × V
Annealed aluminum / copper alloy sheet — soft aluminum alloys / non-ferrous forming sheet	200	0.44×	0.14 × V
Aluminum / aluminium 5052-H32 — Al-Mg alloy / corrosion-resistant sheet	240	0.53×	0.14 × V
Aluminum / aluminium sheet — general sheet alloys in the 250–300 MPa range	280	0.62×	0.16 × V
Aluminum / aluminium alloy 6061-T6 — heat-treated structural sheet	300	0.67×	0.16 × V
Copper / brass sheet — Cu / copper alloys / Cu-Zn brass	300	0.67×	0.14 × V
Low-carbon steel sheet — drawing-quality / cold-rolled forming sheet	400	0.89×	0.16 × V
Carbon / mild steel sheet — S235 / Q235 / ASTM A36 / SS400; hot-rolled / cold-rolled	450	1.00×	0.16 × V
Structural / galvanized steel sheet — GI / zinc-coated carbon steel	500	1.11×	0.17 × V
Structural steel S355 / Q355 — higher-strength carbon steel plate	550	1.22×	0.17 × V
Medium-strength steel sheet — medium-carbon / structural alloy steel	600	1.33×	0.17 × V
Austenitic stainless steel sheet — 304 / 304L / 316 / 316L; Cr-Ni stainless	650	1.44×	0.21 × V
High-tensile steel sheet — HSS / strengthened structural steel	700	1.56×	0.22 × V
High-strength steel S700 — HSLA / high-strength low-alloy plate	800	1.78×	0.22 × V
High-strength alloy steel — quenched / tempered plate in the 850–950 MPa range	900	2.00×	0.22 × V
Ultra-high-strength steel sheet — UHSS / advanced high-strength steel (AHSS)	1000	2.22×	0.22 × V
Hardox 400 / NM400 — abrasion-resistant / wear-resistant steel plate	1250	2.78×	2.5–4 × S

FAQ

Frequently Asked Questions

Practical answers about bending force, V-die selection and machine capacity.

How do you calculate press brake tonnage?

How many tons per meter do I need to bend 3 mm mild steel?

Why does the V-die opening change the bending force?

How does material strength affect the result?

What safety margin should I add when choosing a press brake?

What is the difference between air bending, bottoming and coining?

Choose The Right Press Brake

Share your material, thickness, bend length and tooling details. KRRASS engineers will help match your bending requirements to a suitable press brake and tooling setup.

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Press Brake Tonnage Calculator

Calculate Bending Force

Enter your values

Bending Force Formula

How To Use The Calculator

Worked Example

Press Brake Tonnage Chart

Material Strength Guide

Frequently Asked Questions

How do you calculate press brake tonnage?

How many tons per meter do I need to bend 3 mm mild steel?

Why does the V-die opening change the bending force?

How does material strength affect the result?

What safety margin should I add when choosing a press brake?

What is the difference between air bending, bottoming and coining?

How do you calculate press brake tonnage?

Choose The Right Press Brake

Power your next fabrication line

Press Brake Tonnage Calculator

Enter your values

Bending Force Formula

Worked Example

Frequently Asked Questions

How do you calculate press brake tonnage?

How many tons per meter do I need to bend 3 mm mild steel?

Why does the V-die opening change the bending force?

How does material strength affect the result?

What safety margin should I add when choosing a press brake?

What is the difference between air bending, bottoming and coining?

Choose The Right Press Brake

Power your next fabrication line

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