​Bolts by Grade and Torque

​Reference page for using the right bolt based on grade


​​​One of the biggest mistakes in automotive work, is using the wrong kind of bolt. All automotive manufacturers use grade 8 or higher nuts and bolts on their vehicles. There are many that do not understand bolts by grade and torque specifications. Don't make the mistake thinking that a bolt is a bolt, because they aren't.


I have seen engine brackets break or even rear trailer hitches break off from using the wrong bolts. It is even more common with shock absorbers. I have seen many of shocks come loose because an inferior bolt was used. I have seen head gaskets blow out because a low grade bolt was used to replace a missing factory one. Lower grade bolts can't ​with​stand the torque that higher grades can.


All heads of bolts, have markings and indicators to specify the grade of the bolt. ​It is crucial to use the right kind of bolt per application. Always pay close attention to the head of a bolt to ensure it is the right strength bolt.

​Bolt Grade Markings

US Bolts

bolts by grade and torque

​Metric Bolts

bolts by grade and torque

US Recommended Torque by Grade

Bolt SizeGrade 2 CoarseGrade 2 FineGrade 5 CoarseGrade 5 FineGrade 8 CoarseGrade 8 Fine18-8 S/S Coarse18-8 S/S Fine
1/4"44.76.37.39106.37.8
5/16"89131418201111.8
3/8"1517232633372022
7/16"2427374152583133
1/2"3741576480904345
9/16"535982911151295763
5/8"738311212815918093104
3/4"125138200223282315128124
7/8"129144322355454501194193
1"188210483541682764287289

The above values are in Ft-Lbs

Metric Recommended Torque by Grade

Bolt SizeGrade 8.8Grade 10.9Grade 12.9
M56.99.411.2
M611.715.919.1
M828.438.746.4
M1056.37792
M1298134160
M16244332397
M20476647776
M2482211191342
M30163422232667
M36285538854660

The above values are in ​Nm

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