This page also includes a link to a on line sheet metal bend allowance calculator.
Bend allowance formula in sheet metal.
Lf l1 l2 ba.
Most sheet metal materials will conform to the calculations.
Ba bend allowance.
The bend allowance region is shown in green in my diagram this is a region wherein theory all deformation occurs during the bending process.
The bend allowance formula takes into account the geometries of bending and the properties of your metal to determine the bend allowance.
The material thickness will be measured in decimal form not by the gauge number.
Where ba is bending allowance.
The following illustration shows the equation calculation for determining the bend allowance when forming sheet metal.
If you have a sheet metal bending product as shown in above picture with two legs of length x and y and you unbend it you will see that total length of the unbend sheet will not x y rather the length will be x y ba.