What the Press Brake Tonnage Calculator does
This tool estimates the force a press brake needs to air-bend a part, so you can check a job against your machine before you set it up. Enter the sheet thickness, the V-die opening, the bend length and the material, and it returns the estimated tonnage and force, plus a suggested die opening and the inside radius you can expect. It is built for panel and machine builders matching work to a brake.
The estimate uses the standard air-bending formula, calibrated against published tonnage charts. It runs entirely in your browser and updates as you type.
How to use it
- Enter the sheet thickness and the V-die opening in millimetres.
- Enter the bend length (the length of the bend line).
- Choose the material.
- Read the estimated tonnage and force, with a suggested V-die and the approximate inside radius.
Why use it here
It is free, instant and private, with no sign-up. It gives tonnage, force, a die suggestion and the resulting radius together, which is what you need to plan a bend and pick tooling. Because tonnage is sensitive to setup, keep a margin and confirm against your machine’s chart.
Tip: for the flat blank size of the bent part use the bend allowance calculator, and to weigh the sheet use the metal weight calculator.
Frequently asked questions
- How is press brake tonnage estimated?
- For air bending the tool uses the standard relationship force ≈ 1.42 × tensile strength × length × thickness² ÷ (1000 × V-die opening), then converts to tonnes. It is calibrated so that, for example, 1 metre of 3 mm mild steel in a 24 mm V-die comes out around 24 tonnes, which matches industry charts.
- Why is it called an estimate?
- Real tonnage varies with the die and punch geometry, friction, bend radius, material batch and bottoming versus air bending. Treat the figure as a close planning estimate, keep a safety margin, and check your machine and tooling charts before pushing the limits.
- What V-die opening should I choose?
- A common rule for air bending is a die opening of about 8 times the thickness, which the tool suggests. A wider die lowers the tonnage but increases the inside radius (roughly 0.16 × the die opening); a narrower die does the opposite.
- Does material matter?
- Yes. Tonnage scales with tensile strength, so stainless needs clearly more force than mild steel and aluminium needs less. Pick the material to apply a representative tensile strength.
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Last updated: June 23, 2026