K-Factor Calculator
K-factor locates the neutral axis inside a sheet-metal bend. Use the working calculator to solve K from measured bend allowance or from a bent coupon, then carry that value into bend allowance, bend deduction and flat-pattern layouts.
K-factor formula
K-factor is the neutral-axis offset divided by material thickness. In the bend allowance equation, the same value places the neutral axis inside the bend radius.
BA = theta * (R + K * t)
Back-solving from bend allowance
If measured bend allowance is known, rearrange the formula and solve K directly from bend angle, inside radius and material thickness.
K = (BA / theta - R) / t
Worked example
A 90 degree bend in 2 mm sheet with 3 mm inside radius and measured bend allowance 5.749 mm gives K = (5.749 / 1.5708 - 3) / 2 = 0.330. Treat that as a measured setup value, not a universal material constant.
Frequently asked questions
Is this a different calculator from the sheet-metal K-factor calculator?
No. This is the short search path for the same working calculator at /sheet-metal-k-factor-calculator.
What inputs do I need?
Use bend angle, inside radius and material thickness. If you have a coupon, measure the outside leg lengths and the flat blank length.
Related pages
- K-factor for copper - material-specific notes for copper sheet and copper alloys.
- Sheet-metal K-factor calculator - back-solve K from a measured bend allowance or coupon.
- Bend allowance calculator - use a known K-factor to calculate bend allowance.
- Bend deduction calculator - convert between outside dimensions and flat length.
- What is K-factor? - neutral-axis explanation and formula context.