How to Calculate a Bolt Thread Length

How to calculate the thread length of a bolt

Missed our video? no problem, watch it again now

Posted by Arun Fastener Company Ltd on Wednesday, 16 October 2019

How to calculate a Bolt Thread Length

At Arun Fasteners we are often asked about the thread length on differing size Hex Head Bolts.  Below is a helpful guide.

NOTE: It is measured from UNDER the head

Bolt Thread Length 
0 to 125mm2 x Diameter + 6mm
125 to 200mm2 x Diameter + 12mm
200+mm2 x Diameter + 25mm

We’ve listed below a range of bolt sizes as an example:

Bolt SizeThread Length
M8 x 7022mm
M10 x 18024mm
M12 x 20049mm
M14 x 28053mm
M16 x 19044mm
M18 x 30061mm
M20 x 14065mm
M22 x 36069mm
M24 x 10054mm

Here are some examples of some Bolts we stock-

Metric Hex Bolt
Metric Hex Bolt

Roofing Bolt & Nut
Roofing Bolt & Nut

Metric Coach Bolt & Nut
Metric Coach Bolt & Nut

NOTE: It is measured from UNDER the head