Press Brake Tonnage Calculator

Estimate air-bending force before quoting a formed part. Enter the actual tensile strength, die opening, and equipment ratings, then compare the resulting machine and tooling loads.

Air-bend inputs

Inputs are editable examples. Replace them with your job measurements and shop records.

Use the actual material strength record, not an assumed material preset.

Example 650/450 follows the cited equation. Calibrate only against a documented process.

The displayed machine and tooling ratings are editable examples, not equipment recommendations. Enter the applicable ratings for the actual load distribution.

Estimated bending load

Estimated force
626.46 kN
U.S. short tons
70.42
Tooling line load
17.6 U.S. ton/ft
Machine rating utilization
70.42%
Tool line rating utilization
70.42%

Load comparisons do not establish an acceptable working margin. Confirm the setup against machine and complete tooling documentation.

  • Air-bending estimate only. Confirm material strength, machine load distribution and tooling ratings with the manufacturer; this calculation is not a machine or tooling approval.

Method

This estimate applies to air bending only. Thickness appears squared, so changing thickness has a larger effect than the same proportional change in bend length. A wider die opening lowers the modeled force, but also changes the attainable bend geometry. Enter material strength from the material record, the coefficient supported by your process, and the documented machine and tooling ratings. The example coefficient follows the cited KRRASS equation; it is not a universal calibration.

F (kN) = C × tensile strength (MPa) × bend length (mm) × thickness (mm)² ÷ die opening (mm) ÷ 1,000. Source coefficient C = 650 ÷ 450; enter another coefficient only when supported by your process. Machine utilization (%) = estimated force ÷ entered machine capacity × 100. Tooling line load = estimated force ÷ bend length; utilization compares it with the entered tooling line rating.

Worked example

The cited source example uses 6 mm thickness, 4,000 mm bend length, 48 mm die opening, 450 MPa tensile strength, and C = 650/450. Estimated force is 1,950 kN, approximately 219.19 U.S. short tons. A 2,000 kN machine rating would be 97.5% utilized; that comparison does not itself establish an acceptable working margin.

Limits

The result does not approve a machine setup or choose a working margin. It excludes bottoming, coining, hemming, off-center loading, tooling geometry, local segment limits, deflection, and achievable radius or flange height. Machine capacity and tooling line capacity are different constraints. Check the complete machine, punch, die, holder, and load-distribution instructions against the actual setup before bending.