Sheet Metal Bend Calculator

Enter the sheet thickness, inside bend radius, bend angle and the two outside flange lengths. The calculator gives the bend allowance, bend deduction and the length of flat blank to cut.

Inputs

The bend angle is how far the sheet is bent, so 90° makes an L shape. Flange lengths are measured on the outside, to where the outer faces would meet.

Results

Flat blank length:

K-factor used
Bend allowance (BA)
Outside setback (OSSB)
Bend deduction (BD)
Bend line from flange 1 end

BA = π × A ÷ 180 × (R + K × T). OSSB = tan(A ÷ 2) × (R + T). BD = 2 × OSSB − BA. Flat length = flange 1 + flange 2 − BD. For more bends, subtract one bend deduction per bend.

K-factor depends on material, tooling and the forming method. The automatic value is a common starting rule: 0.33 below R/T of 1, 0.40 up to 3, and 0.50 above. Confirm with a test bend before cutting a batch.

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