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