Bend Deduction Calculator

Bend allowance is the length of material consumed along the neutral axis during the bend. Bend deduction is what you subtract from the sum of the two flange (leg) lengths to get the correct flat pattern length before bending.

K-factor is the ratio of the neutral axis position to the material thickness, and it depends on the material and bending method. Typical values are about 0.33 for mild steel, 0.38 for stainless steel, and 0.40 for aluminum — softer, more ductile materials generally have a higher K-factor.

Flat pattern length = sum of all flange lengths (measured to the outside edges) minus the bend deduction for each bend. This tells you how much flat material to cut before forming.

A tighter bend radius concentrates more stretching in a smaller area, which changes both the bend allowance and bend deduction. Always use the actual tooling radius you'll be bending with, not an assumed value.