Press brake bend calculator, V-die, bend allowance and springback in one pass
Enter the material, thickness, target radius and angle, and read the recommended V-die width, the achievable radius checked against both the tooling and the material, the bend force, the developed length and the springback correction needed to hit the finished angle on the first hit.
Open the bend calculator A Pro account opens this tool. The interface is in English and nothing you enter leaves your browser.How it works
Three steps from material and thickness to a checked bend.
Choose the material, thickness and rolling direction
Pick from mild steel S235JR, annealed stainless 304, or aluminium 5052-H32 and 6061-T6, then enter the sheet thickness. The typical tensile strength for the chosen material fills in automatically and stays editable, and you set whether the bend runs across or with the rolling direction, because the two give different minimum radii for the same sheet.
Set the target radius, angle of rotation and bend length
Enter the inside radius you want and the angle the flange rotates through, not the included angle between the two walls after bending: a 45 degree bend rotation leaves a 135 degree included angle, and mixing the two conventions is the most common first mistake in a flat pattern. Add the length of the bend line and the actual tensile strength if you have a certificate for your batch.
Read the die, the two radius checks, the force and the springback correction
The calculator returns a recommended V-die width, the radius it can achieve with that die, the radius your material can take before cracking, the bend force in tonnes, the minimum flange length, the developed length to add for the bend, and how far past the target angle to press so the sheet springs back to exactly where you want it.
Six numbers from one bend
Enter the geometry once and read every check that matters for the same setup.
Built to catch the mistake before the press does
Most cracked bends and wrong angles trace back to one of a handful of mix-ups. The calculator keeps them apart on purpose.
V-die width from the 8 times T rule, rounded to a real die
The recommended V-die width follows the rule used by press brake tooling makers: about 8 times the sheet thickness, rounded up to a standard size such as 16, 25 or 50 millimetres rather than an arbitrary figure nobody stocks. A narrower V gives a sharper achievable radius but raises the risk of cracking and shortens tool life; a wider V needs less tonnage but cannot reach a tight radius and forces a longer minimum flange.
Radius checked against the die and the material, not just one
The die geometry sets one limit on the radius, roughly the V-width divided by six, and the material sets a separate one that has nothing to do with the die. A 3 millimetre 6061-T6 aluminium sheet in a 25 millimetre V die can be pressed to a geometric 4.17 millimetre radius, but the alloy itself only tolerates 12 to 18 millimetres before it cracks on the outer fibre: the calculator takes the larger of the two limits rather than stopping at the first one it finds.
A springback correction, not just a springback number
Every material opens back up by a few degrees once the press releases it: about 1 to 3 degrees for mild steel, 2 to 5 for annealed 304 stainless, and 3 to 6 for 6061-T6 aluminium, which work hardens fastest of the four. Rather than leaving you to guess, the calculator states the punch angle to press to so the finished part lands on the angle you asked for.
Flange length and bend relief checked in the same pass
The minimum flange length takes the larger of a die clearance rule, half the V-width plus the radius, and a flat four times the thickness rule that fabricators quote regardless of tooling. The same inputs also return the minimum bend relief width and depth and the minimum distance from a hole to the bend line, so a feature placed too close to the fold shows up before the sheet is cut, not after it cracks on the brake.
Frequently asked questions
What is the difference between the geometric radius and the material minimum radius?
The geometric radius comes from the V-die alone, roughly the V-width divided by six, and depends only on the shape of the punch and die. The material minimum comes from how far the alloy can stretch on the outside of the bend before it cracks, and depends on the temper and the rolling direction, not the die. A press can physically close to the geometric radius even when the material cannot survive it, so the real minimum is whichever of the two numbers is larger.
Why does a wider V-die sometimes help and sometimes hurt?
A wider V-die needs less tonnage to close and reaches a larger achievable radius, which matters for a material that cannot take a tight bend. Against that, it cannot produce a sharp corner, and it raises the minimum flange length, because the flange has to cover at least half the V opening plus the radius. Picking the die width is a trade between tonnage, achievable radius and how much flat material the part can spare.
Is the bend angle the same as the included angle between the two walls?
No, and confusing the two is the most common error in a first flat pattern calculation. The angle you enter is how far the flange rotates away from the original flat sheet. The included angle is what is left between the two walls after the bend. For a 90 degree bend the two happen to sit the same distance from a right angle, but for any other angle they diverge: a 45 degree bend rotation leaves a 135 degree included angle, not 45.
Does the calculator give the exact tonnage for my press?
No. The force figure uses a widely published estimate, force per metre equals a constant of about 1.42 times the tensile strength times the thickness squared, divided by the V-width, and that constant varies from about 1.2 to 1.6 between press brake makers depending on friction in the die. It also assumes ordinary air bending: bottoming and coining need substantially more tonnage for the same thickness. Check your press manufacturer's own tonnage chart before ordering tooling.
Is the springback figure measured for my exact batch of material?
No. The ranges shown are typical figures from workshop practice for each material family, not a laboratory measurement of your specific coil or sheet. The real figure depends on the exact chemical composition, the rolling temper and even the temperature of the material on the day. For a short run, press a test piece, measure the angle with a protractor or a gauge, and adjust the die depth from that measurement rather than the typical figure alone.
Does the calculator use the full DIN 6935 bend allowance formula?
No. DIN 6935 publishes minimum bend radius values for cold formed structural steel by thickness and rolling direction, and those inform the material limit shown here. The developed length itself is worked out with the classical K-factor method, where the K-factor places the neutral axis as a fraction of the thickness, rather than the full angle dependent formula in the standard, because that formula is not something the calculator can confirm directly from the published text of the standard.
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