Press Brake Calculators
Practical calculators for your sheet bending jobs. Pick a tool, enter your values and press Calculate.
Bending Force Calculator
Press brake tonnage for air bending.
Results
F = 1.42 × t² × L × Rm / V. A guide value for air bending (about 90°).
- FBending force (tons)
- VV-die opening
- tSheet thickness
- RmMaterial tensile strength
- LBend length
V-Opening Calculator
Minimum, optimal and maximum V-die opening for a material and sheet thickness.
Results
Stainless steel uses about 20% wider dies and aluminum about 20% narrower dies than mild steel. Force is for air bending.
- VV-die opening (optimal, minimum, maximum)
- tSheet thickness
- RiApprox. inside radius ≈ 0.16 × V
Bend Allowance Calculator
Bend allowance, K-factor and flat blank length.
Results
BA = π/180 × θ × (R + K×T). With flat-leg dimensions L = a + b + BA. With outside dimensions L = a + b − BD (BD = 2×OSSB − BA, OSSB = tan(θ/2) × (R + T)). With inside dimensions L = a + b − 2×tan(θ/2)×R + BA. θ is the angle bent through (90 for a 90° bend); K-factor is 0 to 0.5.
- BABend allowance: arc length of the neutral axis
- RInside radius
- TSheet thickness
- KK-factor: neutral axis position (0 to 0.5)
- A′, B′Straight flange lengths up to the start of the bend
Bend Deduction Calculator
Bend deduction, outside setback and flat length.
Results
OSSB = tan(θ/2) × (R + T); BA = π/180 × θ × (R + K×T); BD = 2 × OSSB − BA; Flat length L = A + B − BD. A and B are outside (mold-line) dimensions. For several bends, subtract one BD per bend from the sum of all outside dimensions. K-factor is 0 to 0.5.
- BDBend deduction
- OSSBOutside setback: tangent point to the mold-line apex
- BABend allowance
- A, BOutside (mold-line) dimensions
Min. Flange Length Calculator
Shortest flange that still bends cleanly on a V-die.
Results
b min = 1.1 × V / (2 × sin(A/2)); 1.1 is a safety factor. About 0.78 × V for a 90° bend and about 0.6 × V at 135°; sharp angles need much more flange. If the flange is shorter, choose a narrower V-die (check the extra tonnage with the bending force calculator) or use a special short-flange die.
- MFMinimum flange length
- VV-die opening
- θIncluded angle on the part
Spring Back Calculator
Springback angle, final radius and overbend.
Results
Ri/Rf = 4x³ − 3x + 1, x = Ri·Y/(E·t) (Kalpakjian); Ks = αf/αi = (Ri + t/2)/(Rf + t/2). Springback grows with the radius-to-thickness and yield-to-modulus ratios; high-strength steel, titanium and hard aluminum spring back far more than mild steel. For tight air bends (R < 3t) the elastic formula underestimates. An estimate; real springback varies with material batch and tooling, so confirm with a test bend.
- αiAngle bent on the machine
- αfAngle after release
- Ri, RfInitial and final inside radius
Bump Bending Calculator
Hits, pitch and angle per hit for large-radius step bending.
Results
s = R × θ × π/180; n = ⌈s / p⌉; Δθ = θ / n. Rule of thumb: pitch about half the V-die opening, a V-die no wider than the radius (ideally R/3 or less), and an angle per hit below about 10–15° to avoid visible facets. The flat length of the curved section is the neutral-axis arc: (R + K × t) × θ (radians), with K ≈ 0.5 for large radii.
- RInside radius
- PPitch between hits
- θTotal bend angle
Box Height Calculator
Maximum box height or required upper tool height.
Results
Hbox = 0.672 × (Htool − D); in reverse, Htool = Hbox / 0.672 + D. When the last side of a box is bent, the sides already formed rise up beside the punch; if they are taller than the free height under the beam and clamps, they collide. Tall (box or segmented "finger") tools increase the free height. The 0.672 factor accounts for the rotation of the side during the bend.
- HtoolUpper tool height
- DBeam center to outer edge
- HboxBox internal height
Frequently Asked Questions
How is press brake bending force calculated?
For air bending the approximate formula is F = 1.42 × t² × L × Rm / V, where t is sheet thickness, L bend length, Rm the tensile strength of the material and V the die opening. The Bending Force Calculator returns the result in tons and kN, together with the force per meter.
How do I choose the V-die opening?
As a rule of thumb, use about 6–8 times the thickness for thin sheet and 10–12.5 times for thick sheet. The V-Opening Calculator gives the optimal, minimum and maximum V opening for a thickness, plus the approximate inside radius, minimum flange and force. Stainless steel uses about 20% wider dies and aluminum about 20% narrower dies.
Why does the minimum flange length matter?
If the flange is too short the sheet cannot seat properly on the V-die and the bend fails. For a 90° bend the minimum flange is about 0.78 × V; open angles need less and sharp angles much more. With a short flange, choose a narrower V-die.
What is the difference between bend allowance and bend deduction?
Bend allowance (BA) is the arc length of the neutral axis; with straight flange dimensions the flat length is L = A′ + B′ + BA. Bend deduction (BD) is used with outside dimensions: BD = 2 × OSSB − BA and flat length L = A + B − BD.
Are the calculator results exact?
No, they are guide values. Confirm production decisions with the material certificate, the tooling catalog and a test bend. Contact us for help choosing a machine.
These tools give guide values. Confirm production decisions with the material certificate, tooling catalog and a test bend. For our press brake models, see the press brake page.