When sheet metal is bend, the inside bending surface is compressed. Whereas the outer surface is stretched. As a result, overall sheet length increases. This change in sheet length depends on the position of neutral axis or k-factor. Best way to calculate k factor in sheet metal is by reverse engineering. You can use this K-Factor calculator to calculate k factor using reverse engineering method. Cad tools use k-factor to calculate sheet-metal blank size. You can also use our flat pattern calculator for blank size calculation.

We suggest you also read this article on k-factor and flat pattern calculations. 

How to use This K-Factor Calculator in Sheet Metal

(Reverse Engineering Approach)

Step-1 : Cut a sample sheet and measure it’s total flat length and sheet thickness in mm. Strip width is not very critical.

Step-2 : Bend the sheet to 90 degrees and measure length A and B.

(Please note the bending of sample part is done in the same manner as we are planning for production. Because different machines and bending tools give different k factor values.)

Step-3 : Value of inside bend radius depends on bending tool and die. Generally it is considered equal to sheet thickness.

K Factor Calculator

Facts about K-Factor
  • Inside compression in sheet metal cannot exceed the outside tension. Therefore k-factor value can not exceed “0.5” .
  • Neutral axis cannot go beyond the middle of the sheet thickness.
  • K factor Value is inversely proportional to sheet thickness. Increase in thickness, decreases k-factor value.
  • K-factor value is inversely proportional to material hardness. Therefore with Increase in hardness, K factor value decreases .


To sum up, This calculator can be used to calculate sheet metal K-Factor using reverse engineering method. This k factor is used to calculate sheet metal flat length. 

Got Questions?  We will be happy to help.

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