Calculate the sheet metal K-factor from bend allowance, inside radius, thickness and angle, or find bend allowance from a K-factor such as Inventor’s 0.44.

Angle swept from flat (90ยฐ for an L bend), not the remaining inside opening angle.

Optional settings

Related Calculators

Inventor K Factor Formula

The following formula is used to calculate the K Factor in sheet metal bending:

K = ((BA) / (Aแตฃ) - R) / (T)

Variables:

  • BA is the bend allowance (any consistent length unit)
  • R is the inside bend radius (same length unit as BA)
  • T is the material thickness (same length unit as BA)
  • A is the swept bend angle from flat (degrees), not the remaining inside opening angle
  • A_r is the bend angle in radians (A_r = A \cdot \pi / 180)
  • K is the K Factor

To calculate the K Factor, convert the bend angle from degrees to radians, then apply the formula using the bend allowance, inside radius, and material thickness (using consistent length units).

What is a K Factor?

The K Factor is the neutral-axis distance from the inside bend surface divided by sheet thickness. It is used to estimate flat-pattern bend allowance, rather than to predict the full deformation of the material. Calibrate it with test coupons for the actual material, tooling, bend operation and machine setup.

How to Calculate K Factor?

The following steps outline how to calculate the K Factor:

  1. First, measure the bend allowance (BA).
  2. Next, measure the inside bend radius (R).
  3. Then, measure the material thickness (T).
  4. Measure the bend angle (A) in degrees and convert it to radians (A_r).
  5. Use the formula to calculate the K Factor (K).
  6. After inserting the variables and calculating the result, check your answer with the calculator above.

Example Problem:

Use the following variables as an example problem to test your knowledge.

bend allowance (BA) = 2.10 mm

inside bend radius (R) = 1.00 mm

material thickness (T) = 1.00 mm

bend angle (A) = 90 degrees