O bending force calculator tells you how many tons a press brake needs to bend a sheet. For air bending, force per meter is F = 1.42 × UTS × t² / V: 3 mm mild steel on a 24 mm V-die needs about 24 T per meter. Pick a material, enter thickness and bend length, and get total tonnage, the matching V-die, inside radius, minimum flange and the press brake size to choose.
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Resultados
LiveForça de flexão necessária240 kN · 26.9 US tons
- Force per meter
- 24.4 T/m · 240 kN/m
- Abertura de matriz
- 24 mm (optimal)
- V / thickness ratio
- 8.0 × t
- Inside radius (air bend)
- ≈ 3.8 mm
- Minimum flange (90°)
- 18.7 mm
Inside radius is the natural air-bend radius for the V-die. Add a 20–25% margin to the force when choosing a press brake.
Press brake tonnage formula
For air bending with a standard V-die, the force needed per meter of bend is:
F = 1.42 × UTS × t² × L / (1000 × V)F in kN · UTS in N/mm² · t, L and V in mm. Divide kN by 9.81 for metric tons.
- F bending force (kN)
- UTS ultimate tensile strength of the material (N/mm² = MPa)
- t sheet thickness (mm)
- eu bend length (mm)
- V V-die opening width (mm)
- 1.42 air-bending coefficient
For mild steel (UTS ≈ 450 MPa) this reduces to the familiar shop rule F (T/m) ≈ 65 × t² / V. Force grows with the square of thickness and falls as the V-die gets wider, so doubling the thickness on the same die needs four times the tonnage. Bottoming needs roughly 2–3× and coining 5–8× the air-bending force; the calculator applies 3× and 6×.
How to use the Bending Force Calculator
- Escolha o material. Its tensile strength drives the force; use “Custom” for a mill-certificate value.
- Entre no espessura da folha e o bend length (switch to inch if your drawing is imperial).
- Escolha o die opening slot: Minimum, Optimal (recommended, selected by default) or Maximum from the HARSLE die chart — or Custom to enter the die you actually have.
- Selecione air bending, bottoming or coining, then read the total tonnage and the recommended press brake size.
Worked example
Bend a 1,000 mm long, 3 mm mild steel part on a 24 mm V-die.
- F = 1.42 × 450 × 3² × 1000 / (1000 × 24) = 239.6 kN
- 239.6 kN ÷ 9.81 = 24.4 T (26.9 US tons)
- Inside radius ≈ 0.16 × 24 = 3.8 mm; minimum flange ≈ 0.78 × 24 = 18.7 mm
- With a 25% margin you need at least 30.5 T → a 40-ton press brake handles it comfortably.
The same part in 304 stainless steel needs 35.3 T, and in 5052 aluminum 12.5 T.
Press brake tonnage chart (air bending, per meter)
Metric tons (T) per meter of bend on the optimal V-die from the HARSLE die chart. Multiply by bend length in meters for total force.
| Thickness t (mm) | Min. V (mm) | Optimal V (mm) | Max. V (mm) | Radius at optimal V (mm) | Min. flange (mm) | Mild steel 450 MPa (T/m) | Stainless 304 (T/m) | Aluminum 5052 (T/m) |
|---|---|---|---|---|---|---|---|---|
| 0.5 | 4 | 4 | 6 | 0.6 | 3.1 | 4.1 | 5.9 | 2.1 |
| 1 | 6 | 8 | 10 | 1.3 | 6.2 | 8.1 | 11.8 | 4.2 |
| 1.2 | 8 | 10 | 12 | 1.6 | 7.8 | 9.4 | 13.6 | 4.8 |
| 1.5 | 10 | 12 | 16 | 1.9 | 9.3 | 12.2 | 17.6 | 6.2 |
| 2 | 12 | 16 | 20 | 2.6 | 12.4 | 16.3 | 23.5 | 8.3 |
| 2.5 | 16 | 20 | 24 | 3.2 | 15.6 | 20.4 | 29.4 | 10.4 |
| 3 | 20 | 24 | 30 | 3.8 | 18.7 | 24.4 | 35.3 | 12.5 |
| 4 | 24 | 30 | 40 | 4.8 | 23.3 | 34.8 | 50.2 | 17.8 |
| 5 | 30 | 40 | 50 | 6.4 | 31.1 | 40.7 | 58.8 | 20.8 |
| 6 | 40 | 50 | 60 | 8.0 | 38.9 | 46.9 | 67.8 | 24.0 |
| 8 | 50 | 60 | 80 | 9.6 | 46.7 | 69.5 | 100.4 | 35.5 |
| 10 | 60 | 80 | 100 | 12.8 | 62.2 | 81.4 | 117.6 | 41.6 |
| 12 | 80 | 100 | 120 | 16.0 | 77.8 | 93.8 | 135.5 | 48.0 |
| 14 | 100 | 120 | 160 | 19.2 | 93.4 | 106.4 | 153.7 | 54.4 |
| 15 | 120 | 125 | 130 | 20.0 | 97.3 | 117.3 | 169.4 | 59.9 |
| 16 | 125 | 130 | 160 | 20.8 | 101.1 | 128.3 | 185.3 | 65.6 |
| 18 | 130 | 160 | 200 | 25.6 | 124.5 | 131.9 | 190.6 | 67.4 |
| 20 | 160 | 180 | 200 | 28.8 | 140.0 | 144.8 | 209.2 | 74.0 |
| 22 | 180 | 200 | 220 | 32.0 | 155.6 | 157.7 | 227.8 | 80.6 |
| 25 | 200 | 220 | 250 | 35.2 | 171.2 | 185.1 | 267.4 | 94.6 |
Material strength and bending force factor
| Material | UTS (MPa) | Force vs. mild steel | Typical inside radius |
|---|---|---|---|
| Mild steel S235 / Q235 / A36 | 400–470 | 1,0× | 0.16 × V |
| Structural steel S355 / Q355 | 470–630 | 1.2× | 0.17 × V |
| Stainless steel 304 / 316 | 520–720 | 1.45× | 0.21 × V |
| High-strength steel S700 | 750–950 | 1.8× | 0.22 × V |
| Hardox 400 / NM400 | 1,250 | 2.8× | 2.5–4 × t |
| Alumínio 5052-H32 | 215–265 | 0,5× | 0.14 × V |
| Alumínio 6061-T6 | 290–310 | 0.7× | 0.16 × V |
| Copper / Brass | 220–400 | 0.55–0.8× | 0.14 × V |
Frequently asked questions
How do you calculate press brake tonnage?
Use F = 1.42 × UTS × t² × L / (1000 × V), with F in kN, tensile strength UTS in MPa and thickness t, bend length L and die opening V in mm. Divide by 9.81 to convert kN to metric tons. For mild steel the shortcut is about 65 × t² / V tons per meter.
How many tons per meter do I need to bend 3 mm mild steel?
About 24 tons per meter on a 24 mm V-die (8 × thickness). On the minimum 20 mm die it rises to about 29 T/m, and on the maximum 30 mm die it drops to about 19.5 T/m.
Why does the V-die opening change the bending force?
The V-die is the lever arm. A wider die needs less force but gives a larger inside radius and needs a longer flange; a narrower die gives a tighter radius but needs more tonnage and can mark or crack the sheet. Most shops use V = 6–10 × thickness, typically 8 ×.
How much more force does stainless steel or aluminum need?
Stainless steel 304 needs roughly 1.4–1.5 times the force of mild steel of the same thickness, 5052 aluminum about half, and high-strength steels such as S700 about 1.8 times. Always use the tensile strength from your material certificate when it is available.
What safety margin should I add when choosing a press brake?
Add 20–25% to the calculated force, and check that the force per meter does not exceed the tooling rating. Remember that a short part bent in the middle of the machine still loads the beam locally — never exceed the machine’s rated tons per meter.
What is the difference between air bending, bottoming and coining force?
Air bending presses the sheet into the die without touching the bottom and needs the least force. Bottoming presses the sheet against the die faces (about 2–3× force) for better angle consistency. Coining stamps the punch tip into the material (5–8× force or more) and is only used for thin sheet.
Reviewed by the HARSLE engineering team · Last updated October 2026. Results are engineering estimates; confirm critical values with your machine and tooling documentation.
Força de flexão necessária—
