How Do You Calculate a Flat-Pattern Sheet Metal Layout?

To calculate a flat-pattern sheet metal layout, obtain the Bend Allowance with the following formula: Angle multiplied by Pi divided by 180 multiplied by the sum of the Radius and the K-factor multiplied by the Material Thickness. This yields the Bend Allowance.

There are also Bend Allowance calculators available online, on and There are also different mathematical formulas for determining Bend Allowance. One such formula is Bend Allowance equals Pi over 180 multiplied by Bend Angle, multiplied by the sum of the Inside Radius and the K-factor multiplied by Material Thickness.

To obtain the correct lengths for a flat-pattern sheet metal layout, add the Bend Allowance to each bend area. The flat length of the pattern is equal to the sum of the Bend Allowance and the flange lengths.

Depending on the angle, such as a 90-degree L-bracket, it is potentially easier to obtain the Bend Compensation or Bend Deduction. This entails subtracting two times the Material Thickness plus the bend area, with dimensions being equal to the intersection of the flanges, or the Mold Line.

Bend Deduction formulas require similar values that Bend Allowance formulas do, such as K-factor, Inside Radius, Bend Angle and Material Thickness. Familiarity with each formula provides a well-rounded intimacy with the various ways to calculate flat-pattern sheet metal layouts.