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Bend Allowance Calculator (Online & Free)

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Key takeaways:

1. The bend allowance is a critical parameter in sheet metal fabrication that determines the length of the flat sheet required to achieve the desired dimensions after bending; it varies with material properties, sheet thickness, bending angle, and die used, reflecting the accumulated wisdom and empirical data from experienced mold designers.

2. The article provides practical tools, such as the bend allowance calculator and detailed charts for different materials and thicknesses, to simplify the complex task of calculating flat length for press brake operators, enhancing their efficiency and accuracy in the bending process.

3. Understanding and utilizing the correct bend allowance formula or chart is essential for achieving precise results in sheet metal fabrication, as it compensates for the material stretch and deformation during the bending process, which is vital for the fit and function of the final product.

I. Bend Allowance Calculator

For new press brake operators who may not know how to calculate the bend allowance, a bend allowance calculator has been created to help make their daily work easier.

Related calculator:

Further reading:

II. What Is Bend Allowance?

The bending allowance is a value used to determine the length of the sheet metal after bending.

It varies based on the material, thickness of the sheet, and type of bending die used.

The bending allowance is a statistical value that is derived from the experience and repeated verification of experienced mold designers over the years.

Mold designers can use the calculation formula directly to obtain the unfolding plate size of the bent structure, which is based on the bending allowance data.

III. Bend Allowance Formula

Bend allowance and bend deduction calculations are methods that can be used to determine the length of sheet metal raw materials in the flat form, so as to obtain the desired size of the bending part.

Bend allowance calculation method:

The following equation is used to determine the total flattening length when the bending allowance value is used:

Lt = A + B + BA

Wherein:
·Lt is the total flat length
·A and B are shown in the figure
·BA is the bending allowance value

Bend deduction calculation method:

The following equation is used to determine the total flattening length when using the bend deduction value:

Lt = A + B – BD

Wherein:
·Lt is the total flat length
·A and B are shown in the figure
·BD is the bending deduction value

Other calculation methods for determining the flat length of sheet metal raw materials include using a bending allowance chart, the K-factor, and bending calculations.

IV. Bend Allowance Chart

1. Bend allowance chart for SPCC (mild steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SPCC0.590V40.50.95
1000.73
1350.3
1750.03
  
SPCC0.590V50.51.03
1000.79
1350.33
1750.03
  
SPCC0.590V60.51.1
1000.85
1350.35
1750.03
  
SPCC0.690V40.51.08
1000.83
1350.35
1750.03
  
SPCC0.690V50.51.15
1000.89
1350.37
1750.03
  
SPCC0.690V60.51.23
1000.95
1350.39
1750.03
  
SPCC0.890V60.51.49
1200.73
1350.47
1500.25
  
SPCC0.890V801.64
1200.81
1350.52
1500.27
  
SPCC0.890V1001.79
1200.88
1350.57
1500.3
  
SPCC190V1002.05
1001.58
1201.01
1350.62
1750.06
SPCC190V801.9
1001.47
1200.93
1350.6
1750.05
SPCC190V601.74
1001.35
1200.86
1350.56
1750.05
SPCC1.290V101.42.31
1001.78
1201.13
1350.73
1750.06
SPCC1.290V81.42.15
1001.66
1201.06
1350.69
1750.06
SPCC1.290V61.42
1001.55
1200.98
1350.64
1750.05
SPCC1.590V61.72.36
1001.82
1201.16
1350.75
1750.06
SPCC1.590V121.72.8
1002.17
1201.38
1350.89
1750.08
SPCC1.590V101.72.65
1002.05
1201.31
1350.85
1750.07
SPCC1.590V81.72.5
1001.94
1201.23
1350.8
1750.07
SPCC290V1023.29
1002.54
1201.62
1351.05
1750.09
SPCC290V1223.44
1002.66
1201.69
1351.1
1750.09
SPCC2.590V183.034.6
1003.56
1202.26
1351.47
1750.12
SPCC2.590V123.034.15
1003.21
1202.04
1351.32
1750.11
SPCC2.590V103.034
1003.09
1201.97
1351.28
1750.11
SPCC390V183.133.135.22
1004.03
1202.57
1351.66
1750.14
SPCC390V123.134.78
1003.69
1202.35
1351.52
1750.13
SPCC390V103.134.63
1003.58
1202.28
1351.48
1750.13

2. Bend allowance chart for SUS (stainless steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SUS0.59040.61.04
1000.79
1200.48
1350.3
1750.04
SUS0.59050.61.15
1000.88
1200.54
1350.33
1750.04
SUS0.59060.61.27
1001.13
1200.59
1350.37
1750.04
SUS0.69040.61.16
1000.88
1200.54
1350.34
1750.04
SUS0.69050.61.27
1000.97
1200.59
1350.37
1750.04
SUS0.69060.61.38
1001.05
1200.64
1350.4
1750.05
SUS0.89041.11.4
1001.06
1200.65
1350.4
1750.05
SUS0.89051.11.51
1001.15
1200.7
1350.44
1750.05
SUS0.89061.11.62
1001.23
1200.75
1350.47
1750.06
SUS19061.91.87
1001.42
1200.87
1350.54
1750.07
SUS19081.92.1
1001.6
1200.98
1350.61
1750.07
SUS1.29061.62.1
1001.59
1200.97
1350.61
1750.07
SUS1.29081.62.32
1001.76
1201.08
1350.67
1750.08
SUS1.290101.62.54
1001.93
1201.18
1350.74
1750.09
SUS1.59082.12.68
1002.03
1201.24
1350.77
1750.09
SUS1.590102.12.9
1002.2
1201.35
1350.84
1750.1
SUS29010 3.49
1002.65
1201.62
1351.01
1750.12
SUS29012 3.7
1002.82
1201.72
1351.07
1750.13

3. Bend allowance chart for SPHC (stainless steel)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SPHC190V101.862.05
1001.58
1201.01
1350.62
1750.06
SPHC190V81.861.9
1001.47
1200.93
1350.6
1750.05
SPHC190V61.861.74
1001.35
1200.86
1350.56
1750.05
SPHC1.290V101.442.31
1001.78
1201.13
1350.73
1750.06
SPHC1.290V81.442.15
1001.66
1201.06
1350.69
1750.06
SPHC1.290V61.442
1001.55
1200.98
1350.64
1750.05
SPHC1.590V121.742.8
1002.17
1201.38
1350.89
1750.08
SPHC1.590V101.742.65
1002.05
1201.31
1350.85
1750.07
SPHC1.590V81.742.5
1001.94
1201.23
1350.8
1750.07
SPHC290V122.013.44
1002.66
1201.69
1351.1
1750.09
SPHC290V102.013.29
1002.54
1201.62
1351.05
1750.09
SPHC2.590V1834.6
1003.25
1202.26
1351.47
1750.12
SPHC2.590V1234.15
1003.21
1202.04
1351.32
1750.11
SPHC2.590V1034
1003.09
1201.97
1351.28
1750.11
SPHC390V183.15.22
1004.03
1202.57
1351.66
1750.14
SPHC390V123.14.78
1003.69
1202.35
1351.52
1750.13
SPHC390V103.14.63
1003.58
1202.28
1351.48
1750.13

4. Bend allowance chart for SECC (galvanized steel sheet)

MaterialThicknessBending angleV openingInner radiusBends Allowance
SECC190V101.92.05
1001.58
1201.01
1350.62
1750.06
SECC190V81.91.9
1001.47
1200.93
1350.6
1750.05
SECC190V61.91.74
1001.35
1200.86
1350.56
1750.05
SECC1.290V101.42.31
1001.78
1201.13
1350.73
1750.06
SECC1.290V81.42.15
1001.66
1201.06
1350.69
1750.06
SECC1.290V61.42
1001.55
1200.98
1350.64
1750.05
SECC1.590V121.72.8
1002.17
1201.38
1350.89
1750.08
SECC1.590V101.72.65
1002.05
1201.31
1350.85
1750.07
SECC1.590V81.72.5
1001.94
1201.23
1350.8
1750.07
SECC290V1223.44
1002.66
1201.69
1351.1
1750.09
SECC290V1023.29
1002.54
1201.62
1351.05
1750.09
SECC2.590V183.034.6
1003.56
1202.26
1351.47
1750.12
SECC2.590V123.034.15
1003.21
1202.01
1351.32
1750.11
SECC2.590V103.034
1003.09
1201.97
1351.28
1750.11
SECC390V183.135.22
1004.03
1202.57
1351.66
1750.14
SECC390V123.131.78
1003.69
1202.35
1351.52
1750.13
SECC390V103.134.63
1003.58
1202.28
1351.48
1750.13

5. Bend allowance chart for aluminum plate

MaterialThicknessBending angleV openingInner radiusBends Allowance
AL0.89040.61.15
1000.81
1200.5
1350.36
1750.03
AL0.89050.61.2
1000.85
1200.52
1350.37
1750.03
AL0.89060.61.25
1000.88
1200.54
1350.39
1750.03
AL19060.61.49
1001.05
1206.5
1350.46
1750.04
AL19080.61.59
1001.13
1200.69
1350.5
1750.04
AL1.29060.91.73
1001.22
1200.75
1350.54
1750.04
AL1.29080.91.82
1001.29
1200.79
1350.57
1750.05
AL1.59081.22.18
1001.54
1200.95
1350.68
1750.06
AL1.590101.22.28
1001.61
1200.99
1350.71
1750.06
AL1.590121.22.38
1001.68
1201.03
1350.74
1750.06
AL290141.63.07
1002.17
1201.3
1350.93
1750.08
AL290121.62.98
1002.11
1201.34
1350.95
1750.08
AL290181.63.25
1002.3
1201.42
1351.01
1750.08
AL2.590182.43.89
1002.75
1201.7
1351.21
1750.1
AL390182.54.5
1003.18
1201.96
1351.4
1750.1
AL3.290182.54.74
1003.35
1202.06
1351.47
1750.12
AL490404.66.77
1004.79
1202.95
1352.11
1750.17
AL6.8908009.412.09
1008.55
1205.27
1353.76
1750.31

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