About Bend Allowance and Developed Length

Bend allowance is a method used to calculate the (developed) length of flat sheet metal required to make a bend of a specific radius and angle. The calculation accounts for the thickness of the sheet metal, bend radii, bend angles, and other material properties (like Y- and K-factors).

The developed length calculation also compensates for stretching in the area of a bend. Typically, when you bend or form a piece of sheet metal, the material on the outside of the neutral bend axis stretches while the material on the inside of the neutral bend axis compresses. You can automatically account for this material behavior by establishing appropriate material descriptions and formulae for accurately calculating developed length.

Accurate developed length calculations enable you to capture your design intent in the solid model while also developing a precise flattened model that manufacturers can use when developing the actual product. Make it a practice to determine, in advance, how you calculate developed length.

Use one of the following to calculate the developed length in your designs:

If you do not assign a customized bend table to your part, the following equation is used to calculate developed length:

L = (Π/2 x R + Y factor x T) Θ/90


Where:       L =

Developed length

Π =


R =

Inside radius

    Y factor =

The default Y factor = 0.50

T =

Material thickness

Θ =

Bend angle in degrees (░)

Note: If your developed length calculation is inaccurate, you can override the inaccurate value by directly modifying the value or by assigning a unique bend table to your design.

See Also