Bolt Thread Lengths

Standard Thread Length for Bolts | Inch / Imperial
Bolt Diameter 6" and Shorter Longer Than 6" A325 Thread Length
1/4 0.75 1  
5/16 0.875 1.125  
3/8 1 1.25  
7/16 1.125 1.375  
1/2 1.25 1.5 1
9/16 1.375 1.625  
5/8 1.5 1.75 1.25
3/4 1.75 2 1.375
7/8 2 2.25 1.5
1 2.25 2.5 1.75
1 1/8 2.5 2.75 2
1 1/4 2.75 3 2
1 3/8 3 3.25 2.25
1 1/2 3.25 3.5 2.25
1 3/4 3.75 4  
2 4.25 4.5  
2 1/4 4.75 5  
2 1/2 5.25 5.5  
2 3/4 5.75 6  
3 6.25 6.5  
3 1/4 6.75 7  
3 1/2 7.25 7.5  
3 3/4 7.75 8  
4 8.25 8.5  
*All thread lengths are indicted in inches
Standard Thread Length for Bolts | Metric
Bolt Diameter 125mm and Shorter Longer Than 125mm
M3 12
M4 14
M5 16 22
M6 18 24
M7 20 26
M8 22 28
M10 26 32
M12 30 36
M14 34 40
M16 38 44
M18 42 48
M20 46 52
*All thread lengths are indicated in millimeters

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