Bend Allowance Calculator

Written by Great Medico

Updated September 25, 2026 •2 min read

Share Print Save

A calculator can remove arithmetic without removing judgment. For bend allowance, in solid mechanics, units and geometry often enter with squared, cubed, or fourth-power terms, which makes small input errors unusually costly. Use the result as a transparent model of the fields on this page, not as a substitute for knowing what those fields mean.

What this calculator does

The Bend Allowance Calculator is a focused solver for bend allowance using Bend angle (θ), Inside radius (r), Material thickness (T). Its job is to make the active equation and the quantities feeding it easy to inspect rather than model every possible real-world effect.

How to use it

Begin with Bend angle (θ), Inside radius (r), Material thickness (T), K-factor. Do not strip the units from those values when copying them from a datasheet or measurement. Once calculated, vary the most influential input slightly and confirm that the response agrees with the equation before using the number elsewhere.

How the calculation works

Bend allowance is BA = θ(r+Kt), with bend angle θ in radians, inside radius r, thickness t, and K-factor K. The page also uses setback = tan(θ/2)(r+t) and bend deduction = 2·setback − BA.

Example

Using the default example on the page (Bend angle (θ) = 90 deg; Inside radius (r) = 2 mm; Material thickness (T) = 1 mm; K-factor = 0.33), the calculator returns bend allowance of 0.00366 m. Use the default result as a hand-check point, then test one input at a time so an inverted ratio or unit mistake becomes obvious.

How to interpret the result

Use the bend allowance as a mechanics result tied to the stated load and geometry. If the number feeds a design check, preserve the unit and distinguish calculated nominal/equivalent values from local peaks, test hardness, or code-allowable quantities.

Limitations and notes

Material properties can vary with alloy, processing, temperature, loading rate, direction, and test method; geometric idealizations also matter whenever the real part differs from the entered shape. For this page, verify Bend angle (θ), Inside radius (r) first; a wrong unit or convention there can outweigh any benefit from extra decimal precision. Critical design or acceptance work should still be checked against the applicable standard and measured data.