Sheet Metal Bend Allowance Calculator
Estimate bend allowance from bend angle, inside radius, material thickness and an explicit K-factor assumption before comparing fabrication quotes or CAM flat patterns.
Results
Engineering method
Bend allowance is the arc length of the neutral axis. The neutral-axis radius is modeled as inside radius plus K-factor multiplied by thickness. K-factor depends on material, tooling and bend process and should come from validated shop data for production work.
BA = (π/180) × bend angle × (inside radius + K × thickness).
Professional references
These references establish the standards, technical framework or authoritative engineering context used for this page. Vendor commercial terms are not used as engineering evidence.
- BIPM SI Brochure, 9th edition, updated 2026 — Primary international reference for SI units and unit expression.
- NIST Special Publication 811, Guide for the Use of the International System of Units — U.S. NIST guidance for SI use and unit conversions.
- NIST Digital Thread for Manufacturing — NIST program on standards, conformance testing and trustworthy product-definition data across manufacturing lifecycles.
Commercial independence
PROFENG may display a separately disclosed approved partner after the engineering content. Partner status never changes formulas, conversion factors, procurement criteria, technical references or calculation results. Pending and unapproved programs remain hidden.