Press Brake Tonnage Calculator: Free Air Bending Force Tool
Free engineering tool
Calculate Your Press Brake Tonnage
Estimate V-die air-bending force, then see a practical machine-capacity recommendation.
Machine selection support
Need help choosing the right press brake?
JS RAGOS manufactures CNC press brakes for sheet-metal bending applications. Our team can review your drawing, material, bend length, tooling and production requirements.
Send the part details and calculated tonnage to receive a practical machine and tooling recommendation.
Free engineering tool
Calculate Your Press Brake Tonnage
Estimate V-die air-bending force, then see a practical machine-capacity recommendation.
Machine selection support
Need help choosing the right press brake?
JS RAGOS manufactures CNC press brakes for sheet-metal bending applications. Our team can review your drawing, material, bend length, tooling and production requirements.
Send the part details and calculated tonnage to receive a practical machine and tooling recommendation.
Choosing a press brake by nominal tonnage alone can lead to overloaded tooling, poor bend accuracy, or unnecessary machine cost. This calculator estimates the force required for V-die air bending and then adds a selectable capacity margin. Enter the material, bend length, sheet thickness and target angle. The advanced settings let experienced users change tensile strength, V-opening, punch radius and safety margin.
Press Brake Tonnage by Material and Thickness
| 두께 | V자 개방 | Aluminium 250 MPa | 연강 450 MPa | 스테인리스 600 MPa |
|---|---|---|---|---|
| 1 mm | 6 mm | 5.7 t | 10.2 t | 13.6 t |
| 2 mm | 12 mm | 11.3 t | 20.3 t | 27.1 t |
| 3 mm | 25 mm | 12.2 t | 22.0 t | 29.3 t |
| 4 mm | 32 mm | 17.0 t | 30.5 t | 40.7 t |
| 6 mm | 50 mm | 24.4 t | 43.9 t | 58.6 t |
Preliminary air-bending estimates only. Actual tensile strength and tooling selection can change the required force.
How V-Die Opening Changes Required Tonnage
| V자 개방 | Estimated force | Indicative inside radius | Estimated minimum flange |
|---|---|---|---|
| 24 mm | 40.7 t | 3.84 mm | 14.97 mm |
| 32 mm | 30.5 t | 5.12 mm | 20.63 mm |
| 40 mm | 24.4 t | 6.40 mm | 26.28 mm |
| 50 mm | 19.5 t | 8.00 mm | 33.36 mm |
A wider V-opening reduces force but increases the expected inside radius and flange requirement. Verify the selected die and part geometry.
How to use the press brake tonnage calculator
- Select the material. Mild steel, stainless steel and aluminium include practical default ultimate tensile strength values. For high-strength or custom materials, enter the value from the material certificate.
- Enter the total bend length and sheet thickness. Use the actual length bent in one stroke, not the overall blank size.
- Enter the target inside angle. The angle is checked for tooling feasibility; the standard air-bending force equation is mainly controlled by strength, thickness, bend length and die opening.
- Review the automatically selected V-die opening. You can override it under Advanced settings when the tooling plan requires a different opening.
- Calculate and compare the required force with the recommended rated machine capacity. Confirm the result with the machine and tooling manufacturers before production.
Air-bending tonnage formula
The calculator uses the common V-die air-bending relationship:
Force (kN) = 1.33 × bend length (m) × thickness² (mm) × tensile strength (MPa) ÷ V-opening (mm)
This makes the main relationships easy to understand: force rises in direct proportion to bend length and material strength, rises with the square of thickness, and falls as the V-opening becomes wider. A small increase in sheet thickness therefore has a large effect on the required tonnage.
How the recommended V-opening is selected
For a practical starting point, the calculator selects a standard die opening using a thickness multiplier. It uses approximately 6× thickness below 2.6 mm, 8× from 2.6 mm to below 8 mm, 10× from 8 mm to below 10 mm, and 12× at 10 mm and above. The result is rounded up to an available standard opening. This is guidance, not a tooling approval: flange size, desired inside radius, grain direction, surface condition and tooling capacity can require a different choice.
A wider V-opening reduces tonnage and usually produces a larger inside radius. A narrower V-opening increases tonnage and may allow a smaller flange, but it also increases local stress on the punch, die and workpiece. See our die-opening and tonnage guide 더 자세한 내용은
Worked example: 2 mm mild steel over 1 metre
For 2 mm mild steel with a tensile strength of 450 MPa, a 1,000 mm bend length and a 12 mm automatically selected V-opening, the estimated force is about 199.5 kN, or 20.3 metric tons. Adding the default 15% capacity margin gives 23.4 tons, so the calculator recommends the next listed machine size: 40 metric tons. This margin is not permission to exceed the rated capacity of the tooling or machine.
Worked example: stainless steel needs more force
Using the same 2 mm thickness, 1,000 mm bend length and 12 mm V-opening, but changing the material to stainless steel at 600 MPa, raises the estimate to about 266.0 kN, or 27.1 metric tons. With a 15% margin, the requirement becomes about 31.2 tons and again fits the 40-ton listed capacity. Actual stainless grades vary, so replace the preset with certified tensile strength when accuracy matters.
What machine capacity should you choose?
The result panel separates calculated bending force from recommended rated capacity. The latter applies the chosen margin and rounds upward to a common machine size. Production selection should also consider bed length, daylight, stroke, throat depth, ram and bed deflection, off-centre loading limits, tooling load per metre and the most demanding future part. Browse our CNC 프레스 브레이크, electric press brakes 그리고 heavy-duty press brakes, 또는 send the part drawing to Ragos for a machine and tooling recommendation.
Important engineering limits
This tool is a preliminary estimator for straight V-die air bending. It does not calculate bottoming, coining, hemming, radius tooling, multi-bend tooling, offset tooling or non-uniform load cases. It also cannot account for every batch-to-batch material variation, springback, work hardening or local machine limit. High-strength steel, thick plate, very acute or open angles, short flanges and unusual radius requirements deserve an engineering review. Never use the calculator result to exceed the lower of the machine, punch, die or adapter ratings.
Frequently asked questions
How much press brake tonnage do I need?
Enter the material strength, sheet thickness, bend length and V-opening. The calculator estimates air-bending force, adds your selected margin and rounds up to a listed machine capacity. Final selection must also satisfy tooling and machine load limits.
Does bend angle change the required tonnage?
For standard V-die air bending, material strength, thickness, bend length and V-opening dominate the force estimate. Angle still matters for tooling geometry, springback and feasibility, so the calculator checks it and displays warnings for unusual ranges.
Why does a wider V-die opening reduce tonnage?
A wider opening gives the sheet a larger lever arm during bending, so less force is required. It normally increases the resulting inside radius and minimum flange requirement, so tonnage cannot be considered separately from part geometry.
Can I use this calculator for bottoming or coining?
No. Bottoming and coining use different force assumptions and may require substantially more tonnage. Select those methods only to see the engineering-review notice, then consult the machine and tooling suppliers.
Is the calculated tonnage guaranteed?
No. It is an estimate based on the entered values and a common air-bending equation. Verify actual material certificates, tooling charts, allowable load per metre, machine manuals and test bends before production.
