You will need to know your material thickness mt the bend angle b the inside radius ir and the k factor k.
Bend allowance formula in sheet metal.
Sheet metal calculator bend allowance equations and calculator.
This page also includes a link to a on line sheet metal bend allowance calculator.
Lf l1 l2 ba.
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.
Where ba is bending allowance.
The total length of the flatten sheet is equal to the sum of l1 that s the first length and l2 plus the bend allowance.
The following illustration shows the equation calculation for determining the bend allowance when forming sheet metal.
The bend allowance formula takes into account the geometries of bending and the properties of your metal to determine the bend allowance.