Bend Allowance Calculator

Your details

Selecting a preset fills in a standard K-factor for that material. Choose "Custom" to enter your own.
The stock thickness of the sheet metal measured perpendicular to the surface.
mm
Distance from the inside face of the sheet to the centre of the bend arc. A larger radius produces less deformation and a more accurate K-factor.
mm
The included bend angle (the final angle between the two legs after bending). A 90-degree bend forms a right angle. Enter values between 1 and 179 degrees.
degrees
The flat length of the first flange, measured from the outer mould line to the end of the part. Used to calculate total flat blank length.
mm
The flat length of the second flange. Used together with Leg 1 and the bend allowance to compute the total flat blank length.
mm
Bend allowance (BA)
6.0947mm

Arc length of the neutral axis through the bend zone

Bend deduction (BD)3.9053mm
Outside setback (OSSB)5mm
Flat blank length106.0947mm
K-factor used0.44
Neutral axis radius3.88mm
Bend allowance6.0947
Outside setback5
Bend deduction3.9053

Bend allowance is 6.0947 mm for a 90-degree bend.

  • Inside radius is 1.50x the thickness, a comfortable ratio for most materials and tooling.
  • Bend deduction is 3.9053 mm: subtract this from the sum of your outer mould line dimensions to get the correct flat blank length.
  • K = 0.44 is in the common fabrication range for most steels and aluminium alloys.

Next stepYour flat blank should be 106.0947 mm long. Cut to this length, mark the bend tangent lines, and clamp to your press brake die.

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