K-factor chart.

The Look up a bend panel at the top of the chart gives the K-factor, inside radius and flat length for one bend in one material. It opens on the example below.

1. Material. Pick the grade you are ordering. Grades we only cut flat are still listed, marked Flat only.
2. Thickness. Pick the gauge. K and R change from gauge to gauge because each thickness bends on its own die.
3. Bend angle. How far the flange turns, from 30° to 135°. A square L-bracket is 90°.
4. Outside legs A and B. Each flange measured on the outside, from its edge to the virtual sharp — the point where the two outside faces would meet if the corner were square. Most drawings dimension bends this way.
5. Read the result. K, inside radius, neutral radius, bend allowance, bend deduction, outside setback, minimum flange and punch, ending with Flat length A + B − BD: the blank we cut.

If a leg is shorter than the die's minimum flange, the panel warns you: the bend will not form reliably. Compare materials adds more grades to the same bend, so you can see how the flat length moves when you change material. Switch to mm at the top right, or to Table for every gauge at once.

We modelled the same bracket as a test part in Onshape to show where each number goes, then measured its flat pattern against the calculator.

Onshape keeps thickness, bend radius and K-factor together in one Sheet metal model feature, so the flat pattern updates as soon as you change them. A new model does not know your material: ours opened at a default K of 0.25 and a 0.020″ radius. Always replace both with the row for your grade and gauge.