The **K factor** is the most important and elusive variable of bending, because it varies both as a function of the material and according to parameters such as angle and tooling. The K factor is defined as the **ratio between the material thickness (T) and the neutral fibre axis (t)**, i.e. the part of the material that bends without being compressed nor elongated.

**Bend allowance** is a fundamental parameter to calculate sheet elongation. This is defined as the **length of the neutral fibre** from the beginning to the end of the arc generated by the bend.

** calculate the bend allowance, the K factor** and the derived coefficient called the Y factor, insert the thickness and initial length of the sheet into the cells on the left. After bending the sheet, insert the inner radius, and flanges A and B. Bending angle is 90°.

Thickness T [mm]:

Flat length L [mm]:

internal radius R [mm]:

Flange A [mm]:

Flange B [mm]:

Flat length L [mm]:

internal radius R [mm]:

Flange A [mm]:

Flange B [mm]: