**Table of Contents**show

## Bend Allowance Formula

At the very beginning of the post, I would like to get straight to the point.

**The bend allowance formula is: BA = A* π/180*(R+K*T)**

- BA – Bend Allowance
- A – bend angle in deg
- R – inside bend radius in m
- K – constant
- T – material thickness in m

## What is bend allowance?

The explanation of bending allowance is as follows: a formed sheet metal bending has three dimensions: two outline dimensions and one thickness dimension. Two outline dimensions are defined as L1 and L2, and the thickness dimension is T.

We all know that L1 + L2 is greater than the unfolding length L, and **their difference is the bending allowance**. I define it as K, then the unfolding dimension of a bend L = L1 + L2-K.

**Why is bend allowance important?**

Through the bending coefficient, we can deeply analyze the sheet metal bending conditions of different materials, different bending angles and different bending radii, and we can accurately calculate the unfolded length of various sheet metal bending.

This is very important for sheet metal processing.

## What is bend allowance formula?

Bending allowance and bending deduction calculation are the methods you can choose to use to determine the flattening length of sheet metal raw materials, so as to obtain the required bending part size.

Other methods include bending allowance table, K-factor and bending calculation.

**Further reading:**

## Bend allowance calculation formula

How the formula for bend allowance was created? And how do you calculate bend allowance?

To calculate this bending allowance, you can use the following formula:

**Bending Allowance = A*π/180*(R+K*T)**

This formula considers the different geometries and properties of the parts to be formed.

The most important aspects of this calculation are the material thickness (T), bending angle (A), inner bending radius (R) and K factor of the material to be bent.

It can be seen from the above formula that the bending allowance formula is very simple.

You can get the bending allowance value by substituting the above values into the formula. If the bending angle is 90 °, the bend allowance formula can be simplified to:

*Bending Allowance = π/2(R+K*T)*

Note: for most standard materials and thicknesses, the K factor is usually between 0 and 0.5.

You can use the following K-factor calculator to accurately calculate the value of K-factor.

To facilitate the calculation, you can also scroll down to find the bending allowance calculator to make the calculation.

### Bend allowance formula for aluminum

The bending allowance of aluminum plate is 1.6 times of subtracting a material thickness.

The actual calculation formula of aluminum plate bending: L = L1 + L2-1.6T, in which 1.6T is the bending allowance, which is the empirical value summarized in production.

T is the thickness of aluminum plate, and L1 and L2 are the two bending lengths.

**That is:** subtract 1.6 times the material thickness from the sum of the two bending lengths, which is the expanded size of the aluminum plate.

It should be noted that this formula is only applicable to the bending of aluminum plate whose bending opening is 6 times the thickness of aluminum plate.

## Bend allowance calculator

You can easily get the bending allowance value by using the following bending allowance calculator.

## Bend allowance charts for **steel, aluminum and copper**

The bending allowance table is a table that makes the thickness, bending radius, bending angle, bending allowance or bending deduction value of common materials into a table and saves it in a specified position. It can be easily selected when used.

**Further reading:**

The following tables list the bending allowance of iron, aluminum and copper respectively for reference. You can clearly get the bend allowances required for different material thickness.

### Bending allowance chart for cold rolled steel sheet SPCC (electro galvanized sheet SECC)

TV | Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |

V4 | 90 | 0.9 | 1.4 | 2.8 | ||||||||||

V4 | 120 | 0.7 | ||||||||||||

V4 | 150 | 0.2 | ||||||||||||

V6 | 90 | 1.5 | 1.7 | 2.15 | 4.5 | |||||||||

V6 | 120 | 0.7 | 0.86 | 1 | ||||||||||

V6 | 150 | 0.2 | 0.3 | 0.4 | ||||||||||

V7 | 90 | 1.6 | 1.8 | 2.1 | 2.4 | 5 | ||||||||

V7 | 120 | 0.8 | 0.9 | 1 | ||||||||||

V7 | 150 | 0.3 | 0.3 | 0.3 | ||||||||||

V8 | 90 | 1.6 | 1.9 | 2.2 | 2.5 | 5.5 | ||||||||

V8 | 30 | 0.3 | 0.34 | 0.4 | 0.5 | |||||||||

V8 | 45 | 0.6 | 0.7 | 0.8 | 1 | |||||||||

V8 | 60 | 1 | 1.1 | 1.3 | 1.5 | |||||||||

V8 | 120 | 0.8 | 0.9 | 1.1 | 1.3 | |||||||||

V8 | 150 | 0.3 | 0.3 | 0.2 | 0.5 | |||||||||

V10 | 90 | 2.7 | 3.2 | 7 | ||||||||||

V10 | 120 | 1.3 | 1.6 | |||||||||||

V10 | 150 | 0.5 | 0.5 | |||||||||||

V12 | 90 | 2.8 | 3.65 | 4.5 | 8.5 | |||||||||

V12 | 30 | 0.5 | 0.6 | 0.7 | ||||||||||

V12 | 45 | 1 | 1.3 | 1.5 | ||||||||||

V12 | 60 | 1.7 | 2 | 2.4 | ||||||||||

V12 | 120 | 1.4 | 1.7 | 2 | ||||||||||

V12 | 150 | 0.5 | 0.6 | 0.7 | ||||||||||

V14 | 90 | 4.3 | 10 | |||||||||||

V14 | 120 | 2.1 | ||||||||||||

V14 | 150 | 0.7 | ||||||||||||

V16 | 90 | 4.5 | 5 | 11 | ||||||||||

V16 | 120 | 2.2 | ||||||||||||

V16 | 150 | 0.8 | ||||||||||||

V18 | 90 | 4.6 | 13 | |||||||||||

V18 | 120 | 2.3 | ||||||||||||

V18 | 150 | 0.8 | ||||||||||||

V20 | 90 | 4.8 | 5.1 | 6.6 | 14 | |||||||||

V20 | 120 | 2.3 | 3.3 | |||||||||||

V20 | 150 | 0.8 | 1.1 | |||||||||||

V25 | 90 | 5.7 | 6.4 | 7 | 17.5 | |||||||||

V25 | 120 | 2.8 | 3.1 | 3.4 | ||||||||||

V25 | 150 | 1 | 1 | 1.2 | ||||||||||

V32 | 90 | 7.5 | 8.2 | 22 | ||||||||||

V32 | 120 | 4 | ||||||||||||

V32 | 150 | 1.4 | ||||||||||||

V40 | 90 | 8.7 | 9.4 | 28 | ||||||||||

V40 | 120 | 4.3 | 4.6 | |||||||||||

V40 | 150 | 1.5 | 1.6 |

### Bending allowance chart for aluminum plate

TV | Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |

V4 | 1.4 | 2.8 | ||||||||||||

V6 | 1.6 | 4.5 | ||||||||||||

V7 | 1.6 | 1.8 | 5 | |||||||||||

V8 | 1.8 | 2.4 | 3.1 | 5.5 | ||||||||||

V10 | 2.4 | 3.2 | 7 | |||||||||||

V12 | 2.4 | 3.2 | 8.5 | |||||||||||

V14 | 3.2 | 10 | ||||||||||||

V16 | 3.2 | 4 | 4.8 | 11 | ||||||||||

V18 | 4.8 | 13 | ||||||||||||

V20 | 4.8 | 14 | ||||||||||||

V25 | 4.8 | 5.4 | 6 | 17.5 | ||||||||||

V32 | 6.3 | 6.9 | 22 |

### Bending allowance chart for copper plate

TV | Angle | 0.6 | 0.8 | 1 | 1.2 | 1.5 | 2 | 2.5 | 3 | 3.5 | 4 | 4.5 | 5 | Shortest size |

90 | 3.6 | 5.2 | 6.8 | 8.4 | 28 | |||||||||

120 | ||||||||||||||

150 |

**Note:**

- The V12 coefficient for 2mm C profile is 3.65 and that for other 2mm plates is 3.5). The edge folding bend allowance for 2mm plate is 1.4;
- The bend allowance for 6mm copper plate is 10.3;
- The bend allowance for 8mm copper plate is12.5;
- The bend allowance for 10mm copper plate is 15;
- The bend allowance for 12mm copper plate is 17;
- The bend allowance for 3.0 stainless steel with V25 die is 6;
- The bend allowance for 3.0 stainless steel with V20 die is 5.5;
- (The copper bars exceeding 6mm all use the bending allowance of V40 lower die)