01 / ALLOWANCEBA
Account for the bend.
Add the length along the neutral axis to the straight sections of your flat pattern.
Open toolSHEET METAL, FIGURED OUT
Know your bend.
Before you cut.
Bend allowance, deductions, and the numbers in between. A clearer way to work from sheet to shape.
Free to calculate. No account needed.
01 /Formulas you can follow
02 /Millimeters or inches
03 /Calculated on your device
LESS GUESSWORK. MORE CLARITY.YOUR WORKBENCH
A good fit starts here.
Adjust the inputs. See the relationship.
Keep the calculation.
02 / THE GEOMETRY
Neutral axisCross-section · not to scale
03 / YOUR RESULT
Bend allowance BA
The flat length through the bend.
Bend deduction BD3.602mm
Outside setback OSSB4.000mm
THE FORMULA
BA = α × (R + K × T)Understand the calculation ONE BEND AT A TIMEα is the bend angle in radians. Illustration range: 15–150°. Results depend on your material and tooling inputs.
THE ESSENTIALS, CONNECTED
Different numbers.
The same piece
of metal.
Understand what each value tells you, and where it belongs in the job.
Work through an example02 / DEDUCTIONBD
Work from the outside.
Relate properly defined outside dimensions to the length of the unfolded part.
Open tool03 / CALIBRATIONK
Use your shop’s numbers.
A K-factor is tied to a process. A measured test bend gives it real context.
Open tool04 / THICKNESSGA
Know the sheet.
Gauge is a nominal reference. Measured thickness is the better calculation input.
Open toolTHE METHOD MATTERS
A number is only
as good as
its assumptions.
Keep the geometry visible.
Keep the inputs accountable.
01Allowance adds. Deduction subtracts.
For a single bend, allowance is the length through the curved section. Deduction is subtracted from the sum of the two outside mold-line dimensions.
BA = α × (R + K × T)BD = 2 × OSSB − BA02Your K-factor needs context.
Material, thickness, radius, and tooling all matter. The example uses K = 0.4 to explain the relationship. It is not a recommended production setting.
Use a value from a measured test bend under the same process conditions.
03Check the process, not just the decimal.
More decimal places do not make an unknown input more reliable. Confirm your dimensions, angle convention, and material data, then check against a test piece and your drawing’s tolerance.