Physics

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Bend Allowance Calculator.

Calculate sheet-metal bend allowance with an explicit K-factor.

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Set your values

Results update as you type.

02 / ANSWER

Material thickness

Inside bend radius

Bend angle

K-factor

bendAllowance

0.000000

neutralRadius

0.000000

Use Cases

Flat pattern development for sheet metal parts

Determine the required flat blank length before bending, ensuring accurate final dimensions after forming.

Example: For a 2 mm thick steel plate with a 3 mm inside radius and 90° bend, using K=0.44, the bend allowance is calculated.

Comparing K-factor values for different materials

Evaluate how different K-factors affect the bend allowance for the same geometry, helping select the right material or process.

Example: Change K-factor from 0.3 to 0.5 and observe the change in bend allowance for a given thickness and radius.

Frequently Asked Questions

What is bend allowance in sheet metal?: Bend allowance is the length of the neutral axis of the material that is consumed by the bend. It is used to calculate the flat pattern length needed to produce a bent part with the desired dimensions.
How do I determine the K-factor for my material?: The K-factor is the ratio of the neutral axis location to the material thickness. It depends on material type, thickness, bend radius, and bending method. Common values range from 0.3 to 0.5. For precise results, consult material data or perform test bends.
What units does this calculator use?: This calculator uses millimeters for material thickness and inside bend radius, and degrees for the bend angle. The K-factor is a dimensionless number between 0 and 1.

Tips & Common Mistakes

Tips

Ensure material thickness and inside bend radius are in millimeters for consistent results.
Use a K-factor value that matches your material and bending process; typical values are 0.3 to 0.5.
For bend angles greater than 90 degrees, the bend allowance increases; verify with test bends.
Always double-check your input values for accuracy, as small errors can affect the flat pattern length.

Common Mistakes to Avoid

Using the outside bend radius instead of the inside bend radius.
Entering the bend angle in radians instead of degrees.
Assuming a fixed K-factor for all materials without verification.

Last updated: August 13, 2026

Use Cases

Flat pattern development for sheet metal parts

Determine the required flat blank length before bending, ensuring accurate final dimensions after forming.

Example: For a 2 mm thick steel plate with a 3 mm inside radius and 90° bend, using K=0.44, the bend allowance is calculated.

Comparing K-factor values for different materials

Evaluate how different K-factors affect the bend allowance for the same geometry, helping select the right material or process.

Example: Change K-factor from 0.3 to 0.5 and observe the change in bend allowance for a given thickness and radius.

Frequently Asked Questions

What is bend allowance in sheet metal?

Bend allowance is the length of the neutral axis of the material that is consumed by the bend. It is used to calculate the flat pattern length needed to produce a bent part with the desired dimensions.

How do I determine the K-factor for my material?

The K-factor is the ratio of the neutral axis location to the material thickness. It depends on material type, thickness, bend radius, and bending method. Common values range from 0.3 to 0.5. For precise results, consult material data or perform test bends.

What units does this calculator use?

This calculator uses millimeters for material thickness and inside bend radius, and degrees for the bend angle. The K-factor is a dimensionless number between 0 and 1.

Tips & Common Mistakes

Tips

Ensure material thickness and inside bend radius are in millimeters for consistent results.
Use a K-factor value that matches your material and bending process; typical values are 0.3 to 0.5.
For bend angles greater than 90 degrees, the bend allowance increases; verify with test bends.
Always double-check your input values for accuracy, as small errors can affect the flat pattern length.

Common Mistakes to Avoid

Using the outside bend radius instead of the inside bend radius.
Entering the bend angle in radians instead of degrees.
Assuming a fixed K-factor for all materials without verification.

Use Cases

Flat pattern development for sheet metal parts

Determine the required flat blank length before bending, ensuring accurate final dimensions after forming.

Example: For a 2 mm thick steel plate with a 3 mm inside radius and 90° bend, using K=0.44, the bend allowance is calculated.

Comparing K-factor values for different materials

Evaluate how different K-factors affect the bend allowance for the same geometry, helping select the right material or process.

Example: Change K-factor from 0.3 to 0.5 and observe the change in bend allowance for a given thickness and radius.

Frequently Asked Questions

What is bend allowance in sheet metal?

How do I determine the K-factor for my material?

What units does this calculator use?

This calculator uses millimeters for material thickness and inside bend radius, and degrees for the bend angle. The K-factor is a dimensionless number between 0 and 1.

Tips & Common Mistakes

Tips

Ensure material thickness and inside bend radius are in millimeters for consistent results.
Use a K-factor value that matches your material and bending process; typical values are 0.3 to 0.5.
For bend angles greater than 90 degrees, the bend allowance increases; verify with test bends.
Always double-check your input values for accuracy, as small errors can affect the flat pattern length.

Common Mistakes to Avoid

Using the outside bend radius instead of the inside bend radius.
Entering the bend angle in radians instead of degrees.
Assuming a fixed K-factor for all materials without verification.