Single Bend Flat Length Calculator
Calculate neutral-axis bend allowance and flat length from entered outside flange dimensions and K factor.
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Result
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Calculation steps
Work through one step at a time or reveal the complete calculation. The steps use your current inputs.
How to calculate
Calculate neutral-axis arc length, outside setback and bend deduction. Subtract the deduction from the sum of outside flange dimensions.
BA=angle_rad×(inside radius+K×thickness); setback=(radius+thickness)tan(angle/2); flat=A+B−2×setback+BA
Worked example
For thickness 1, radius 0, K 0.5, direction change 90° and outside flanges 10+10, allowance is π/4 and flat length is about 18.7853982 in the same length unit.
Assumptions and input details
A single ideal bend using an entered empirical K factor; material/process prediction and minimum-radius selection are excluded. Angle 0 means flat and 90 means a right-angle direction change. Outside flanges must reach their tangent setbacks. No springback, tooling clearance, multiple-bend interference or manufacturing guarantee.
References: Autodesk: K-factor sheet rules · Autodesk: unfold equations
Unit definitions
Unit selection is independent of language. Each selector contains only units for its physical quantity. Calculations use defined base units internally.
Choose from 23 length definitions, including explicitly labelled regional measures. Area conversions square the length factor; geometric volumes cube it.
Regional measures are not interchangeable merely because their names look similar. This is a documented selection, not a claim to include every historical unit.
NIST measurement tables · Japanese traditional units · Mainland China and Hong Kong unit distinctions
Using this calculator
Can I enter my own problem?
Yes. Replace the example values with your own inputs. The result, calculation steps, tables and applicable diagrams update from those inputs. Blank or invalid values clear the result; example values are never silently substituted for missing inputs.
Are the results exact?
Results use floating-point arithmetic and displayed rounding. Read the formula, assumptions and any stated data precision before interpreting the result.
Is my input uploaded?
The calculation runs in your browser. No account, file upload or external AI service is required. Inputs are not saved between page reloads.
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