K Factor For Bending Calculator

Work out k factor for bending instantly with clear inputs, formula shown and shareable results.

About K Factor For Bending Calculator

K-factor is derived by working the bend allowance formula backwards. Dividing measured allowance by the bend angle in radians gives the neutral axis radius; subtracting the inside radius and dividing by thickness gives K as the fraction of thickness at which the neutral axis sits. The Y-factor used by some CAD systems is simply K times pi over two.

Formulas

K-factor

K = (BA / angle in radians - R) / T

Y-factor

Y = K x pi / 2

Worked example

With the default values below, K Factor For Bending Calculator returns K-factor of 0.0000. Change any input above and every figure here is recalculated in your browser.

Inputs used

Measured bend allowanceminimum 0.01 mm: 4.5 mm
Bend angleaccepts 1–179 °: 90 °
Inside bend radiusminimum 0.1 mm: 3 mm
Material thicknessminimum 0.1 mm: 2 mm

Results

K-factor: 0.0000
Neutral axis radius: 2.865 mm
Neutral axis offset from inside: -0.135 mm
Y-factor: 0.0000

Step by step

1Values used
2K-factor
3Y-factor
4K-factor= 0.0000
5Neutral axis radius= 2.865 mm
6Neutral axis offset from inside= -0.135 mm
7Y-factor= 0.0000

Assumptions and limits

The result is derived only from the 4 inputs listed above. Anything not among them is not part of the calculation.
In particular, this calculator does not take inflation, tax, fees or charges or compounding frequency into account.
Figures are rounded for display to 4 decimal places, so totals built from several rounded parts can differ slightly from the unrounded arithmetic.

How these calculators are built and tested is described on the Methodology page. If a figure looks wrong, please report it.

Frequently Asked Questions

How is the K Factor For Bending figure worked out?

K = (BA / angle in radians - R) / T. K-factor is derived by working the bend allowance formula backwards.

How do I get a measured bend allowance?

Bend a test piece, measure the two outside flanges and the overall flat length, then BA = flat length - (flange A + flange B - 2 x setback). One test per material and tooling combination is enough.

What values do I need to enter?

This calculator takes 4 inputs: Measured bend allowance, Bend angle, Inside bend radius, Material thickness. The pre-filled defaults are a realistic worked example — replace them with your own site or project figures.