Sheet Metal Bend Allowance (BA), Outside Setback & Bend Deduction Calculator

Develop accurate press-brake flat patterns using K-Factor, radius, and thickness.

Bend Allowance (BA)
5.31 mm
Bend Deduction (BD = 2·OSSB − BA) 3.69 mm
Outside Setback (OSSB) 4.5 mm
Neutral Axis Radius (R + K·T) 3.38 mm
Inputs
mm
Sheet metal thickness (T) in millimeters.
mm
Press brake inside bend radius (R) in millimeters.
deg
Included bend angle in degrees (90° for a right-angle flange).
K
Neutral axis K-Factor (0.33 air bend soft, 0.44 standard mild steel).
Results & Graph
Bend Allowance (BA)
5.31 mm
Bend Deduction (BD = 2·OSSB − BA)
3.69 mm
Outside Setback (OSSB)
4.5 mm
Neutral Axis Radius (R + K·T)
3.38 mm

Bend Allowance (BA)

Graph 1 • Material Thickness Mm Sensitivity Recalculates the domain equation across 50% to 150% of the primary input while holding other parameters constant.
0 mm 3.2 mm 6.5 mm 50%: 4.62 mm 4.6 50% 75%: 4.96 mm 5.0 75% 100%: 5.31 mm 5.3 100% 125%: 5.65 mm 5.7 125% 150%: 6 mm 6 150%
Graph 2 • Primary & Supporting Metric Comparison Compares the primary output alongside supporting domain benchmarks.
Bend Allowance (BA) 5.31 mm Bend Deduction (BD = 2·OSSB − BA) 3.69 mm Outside Setback (OSSB) 4.5 mm Neutral Axis Radius (R + K·T) 3.38 mm
Graph 3 • Exact Output Table & Units Displays each calculated output in its exact domain unit.
Bend Allowance (BA)5.31 mmBend Deduction (BD = 2·OSSB − BA)3.69 mmOutside Setback (OSSB)4.5 mmNeutral Axis Radius (R + K·T)3.38 mm
Summary: For 2 mm sheet metal bent 90° over R=2.5 mm (K=0.44), Bend Allowance is 5.309 mm, Outside Setback is 4.5 mm, and Bend Deduction is 3.691 mm.
Summary: For 2 mm sheet metal bent 90° over R=2.5 mm (K=0.44), Bend Allowance is 5.309 mm, Outside Setback is 4.5 mm, and Bend Deduction is 3.691 mm.
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Formula & Mathematical Methodology: Sheet Metal Bend Allowance Formula

BA = (π / 180) × Angledeg × (InsideRadius + K × Thickness)
OSSB = tan(Angle/2) × (InsideRadius + Thickness)
BD = 2·OSSB − BA
BA = (π / 180) × Angle_deg × (InsideRadius + K × Thickness); OSSB = tan(Angle/2) × (InsideRadius + Thickness); BD = 2·OSSB − BA
  • materialThicknessMm: Material Thickness Mm (mm)
  • insideBendRadiusMm: Inside Bend Radius Mm (mm)
  • bendAngleDeg: Bend Angle Deg (deg)
  • kFactorNeutralAxis: K Factor Neutral Axis (K)

Rounding: Physical package counts round up where appropriate; continuous measurements round to 2 decimal places.

Worked Example: Practical Benchmark: Sheet Metal Bend Allowance

Develop accurate press-brake flat patterns using K-Factor, radius, and thickness.

  1. Enter your project dimensions, machining speeds, or recipe weights.
  2. Compute the governing equation: BA = (π / 180) × Angle_deg × (InsideRadius + K × Thickness); OSSB = tan(Angle/2) × (InsideRadius + Thickness); BD = 2·OSSB − BA.
  3. Review the primary result, supporting dimensions, and 3 SVG visualizations.
Result: Computes Sheet Metal Bend Allowance via BA = (π / 180) × Angle_deg × (InsideRadius + K × Thickness); OSSB = tan(Angle/2) × (InsideRadius + Thickness); BD = 2·OSSB − BA.

Frequently Asked Questions

How does the Sheet Metal Bend Allowance (BA), Outside Setback & Bend Deduction Calculator calculate results?

It evaluates BA = (π / 180) × Angle_deg × (InsideRadius + K × Thickness); OSSB = tan(Angle/2) × (InsideRadius + Thickness); BD = 2·OSSB − BA directly in your browser and plots three custom SVG visualizations.

Can I compare different material dimensions or batch sizes side by side?

Yes. Click "Compare (0/3)" in the results toolbar to pin up to 3 scenarios side by side.

Can I print a clean shop or kitchen reference sheet?

Yes. Click the Print button in the results toolbar for a distraction-free worksheet.

Science & Engineering · Mechanical & Shop Engineering

Sheet Metal Bend Allowance (BA), Outside Setback & Bend Deduction Calculator: inputs, method, and how to read the result

Develop accurate press-brake flat patterns using K-Factor, radius, and thickness.

Choose inputs for the case you are checking

The defaults are illustrative. Replace them with values for your case and keep the units shown beside each field.

  • Material Thickness Mm: Sheet metal thickness (T) in millimeters.
  • Inside Bend Radius Mm: Press brake inside bend radius (R) in millimeters.
  • Bend Angle Deg: Included bend angle in degrees (90° for a right-angle flange).
  • K Factor Neutral Axis: Neutral axis K-Factor (0.33 air bend soft, 0.44 standard mild steel).

What the calculation includes

With the default values shown, Bend Allowance (BA) is 5.31 mm. The calculation follows Sheet Metal Bend Allowance Formula; the formula and variable definitions above show how the inputs combine.

One-input check: With the other defaults held constant, changing Material Thickness Mm from 2 mm to 3 mm changes Bend Allowance (BA) from 5.31 mm to 6 mm. This is a comparison inside the calculator's stated model, not a prediction.

Where to use caution

  • Uses standard North American & metric trade dimensions, Machinery’s Handbook formulas, and culinary weight ratios.
  • Verify local municipal building codes, tool manufacturer limits, and food-safety time/temperature tables before execution.

Scope: Trade, Shop & Culinary Science Reference Standard Check the assumptions and limitations against your situation before relying on the estimate.

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