K-Factor Calculator (Reverse)
The practical way to get a K-factor is to reverse it from a real bend: measure the two outside flange lengths and the flat, and this tool solves for the K that your tooling actually produced. Enter the outside dimensions, thickness, inside radius and bend angle, and it returns bend deduction, bend allowance and the implied K.
Measure A and B to the outside mould lines (the theoretical sharp corner), not to the tangent points. The implied K is the value your tooling actually produced — use it to unfold the next part with the same die, thickness and radius, and it will come out right the first time.
Questions about the K-factor
BD = A + B − flat; BA = 2 × tan(θ/2) × (R + t) − BD; K = (BA ÷ (θ·π/180) − R) ÷ t.
Why reverse a K-factor instead of looking it up?
Because tables give you a starting value, and your tooling gives you the truth. A K reversed from a real bend on the actual die, thickness and radius will unfold the next part with that setup correctly the first time — a table value is an estimate until it is confirmed against a bend.
What if the implied K comes out above 0.5 or below 0.25?
Check the measurement first: dimensions must be to the outside mould lines, and the flat must be from the same bend. A K above 0.5 usually means the flat was measured long or the radius is larger than assumed; below 0.25 usually means a much sharper inside radius than entered.
Is this the same K your press brakes use?
Our brakes are programmed with tooling-specific values from the same kind of test bends. When we quote, the flat pattern is unfolded with the value for the die and material that will run the part — which is why the flat you approve matches the part that arrives.
Keep going
Calculators — enter dimensions, get a number
Sheet Metal Weight CalculatorWeight per piece and per batch from L × W × t, with real alloy densities.Bend Allowance CalculatorThe neutral-axis length through a bend, from thickness, radius, angle and K-factor.Sheet Metal Cost CalculatorWhere a part’s cost actually sits — material, cutting, forming, finishing and setup.Press Brake Tonnage CalculatorBending force in kN and tons from thickness, material and bend length, with a 20% margin.Hole-to-Bend Distance CalculatorMinimum hole-to-bend and hole-to-edge clearances from thickness and inside radius.Charts and checklists — read, print, work through
Sheet Metal Gauge to mm ChartSteel (MSG) and aluminium (B&S) gauge dimensions, and why we quote in mm.Sheet Metal DFM ChecklistThe 24 checks we run on a drawing before we quote it, grouped and explained.Sheet Metal RFQ ChecklistThe 12 items that make an RFQ quotable in one round, with the reason each matters.Sheet Metal Supplier Audit Checklist13 remote-verifiable checks for a sheet metal supplier, in four passes.Reverse your K — we unfold with ours
Upload the part and our engineers unfold it with the tooling-specific K programmed for the press brake that will run it, then flag anything that will not come out flat the first time.
Quote within 24h · Engineer reply in 24h