Bolt torque chart: SAE Grade 2, 5 and 8

At 75% of proof load, a 3/8-16 bolt takes 20 ft-lb in Grade 2, 31 ft-lb in Grade 5 and 44 ft-lb in Grade 8, dry; oiled threads take a quarter less. The chart covers 1/4" to 1-1/2" in coarse (UNC) and fine (UNF) thread.

Sources checked

Torque at 75% of proof load. Dry: K 0.20. Oiled: K 0.15.

Units
ThreadGrade 2Grade 5Grade 8
DryOiledDryOiledDryOiled
1/4-20coarse5.57.44.15.68.411.56.38.611.916.28.912.1
1/4-28fine6.38.54.76.49.713.17.39.813.718.510.213.9
5/16-18coarse11.315.38.411.417.423.613.017.724.633.318.425.0
5/16-24fine12.516.99.412.719.326.214.519.627.236.920.427.7
3/8-16coarse20.027.115.020.330.941.923.231.443.659.132.744.3
3/8-24fine22.630.717.023.035.047.426.235.649.467.037.050.2
7/16-14coarse32.043.324.032.549.467.037.150.269.894.652.370.9
7/16-20fine35.748.426.836.355.274.841.456.177.910658.479.2
1/2-13coarse48.866.136.649.675.410256.576.710614479.8108
1/2-20fine55.074.641.355.985.011563.886.412016390.0122
9/16-12coarse70.495.452.871.610914781.6111154208115156
9/16-18fine78.510658.979.812116491.0123171232128174
5/8-11coarse97.113272.898.7150203113153212287159215
5/8-18fine11014982.5112170230128173240325180244
3/4-10coarse172233129175266361200271376509282382
3/4-16fine192261144196297403223302420569315427
7/8-9coarse167226125170430582322437606822455617
7/8-14fine184249138187473642355481668906501679
1-8coarse2503391872546448734836559091,232682924
1-12fine2733712052787049555287169951,3487461,011
1-1/8-7coarse3544802663607941,0775958071,2881,7469661,309
1-1/8-12fine3975392984048911,2086689061,4451,9581,0831,469
1-1/4-7coarse5006773755081,1201,5198401,1391,8172,4631,3631,848
1-1/4-12fine5537504155631,2411,6829301,2622,0122,7281,5092,046
1-3/8-6coarse6558884916661,4691,9921,1021,4942,3823,2301,7872,422
1-3/8-12fine7461,0115597581,6732,2681,2541,7012,7123,6772,0342,758
1-1/2-6coarse8691,1796528841,9492,6431,4621,9823,1614,2862,3713,215
1-1/2-12fine9781,3267349952,1942,9741,6452,2313,5574,8232,6683,617

Grade 2 proof stress is 55,000 psi up to 3/4" and 33,000 psi above. The 1/4"–3/4" values apply to bolts 6" long or shorter; longer ones are held to the lower Grade 1 values. Grade 5 proof stress is 85,000 psi up to 1" and 74,000 psi above. Open a size for zinc-plated and waxed values and clamp loads:

How to read the chart

Find the bolt’s diameter and threads per inch on the left, then its grade across the top: no marks on the head is Grade 2, three radial lines is Grade 5, six is Grade 8 (bolt grade markings). Take the dry value for clean, unlubricated threads and the oiled value when the threads and nut face are oiled.

Every value is the torque that clamps the bolt to 75% of its proof load, worked out with T = K × D × F: K 0.20 dry and 0.15 oiled, D the nominal diameter in inches, F the clamp load in pounds. Those are the same assumptions as Fastenal’s published chart, and the numbers match it. To change any of them, use the bolt torque calculator.

Where these numbers stop

A maker’s spec beats the chart

Engine, brake, suspension and wheel fasteners have specs of their own, often for a joint or gasket that needs less clamp than a bare bolt could take. Use the chart for general-purpose steel bolts where no spec exists.

The grades here are SAE J429. Stainless, brass and aluminum bolts aren’t covered, and neither are torque-to-yield bolts, which are tightened by angle to the maker’s procedure.

Questions

How much torque does a Grade 8 bolt need?

At 75% of proof load, dry: 44 ft-lb for 3/8-16, 106 ft-lb for 1/2-13 and 212 ft-lb for 5/8-11. Oiled threads take a quarter less. Grade 8 has a proof stress of 120,000 psi at every size up to 1-1/2".

Why does a 7/8" Grade 2 bolt get less torque than a 3/4" one?

SAE J429 drops Grade 2’s proof stress from 55,000 psi to 33,000 psi above 3/4", so the bigger bolt is allowed less stress. The chart follows the standard; it isn’t a typo.

Is fine thread torque higher?

Slightly. A fine thread has a larger stress area, so it carries a higher clamp load for the same grade, and the torque rises with it: a 3/8-24 Grade 5 bolt takes 35 ft-lb dry against 31 for 3/8-16.

What about zinc-plated or waxed bolts?

Zinc-plated bolts are close to dry (K 0.17–0.22). Waxed nuts, as supplied with some high-strength nuts, take about half the dry torque (K 0.10). Each size page lists those too.

Sources

  1. Portland Bolt: SAE J429: proof load, yield and tensile strength for Grades 2, 5 and 8 (checked October 14, 2026)
  2. Portland Bolt: Thread pitch chart: UNC and UNF threads per inch and tensile stress areas (checked October 14, 2026)
  3. Fastenal: Mechanical properties of inch fasteners, with UNC and UNF tensile stress areas (checked October 14, 2026)
  4. Fastenal: Torque–tension relationship for A307 A, Grade 5, 8 and 9 coarse thread bolts (75% of proof load; K 0.15 and 0.20) (checked October 14, 2026)
  5. Portland Bolt: Bolt torque chart: T = KDP at 75% of proof load, with K for plain, waxed and galvanized bolts (checked October 14, 2026)
  6. Fastenal: Bolted joint design: nut factor (K) by finish and how much preload varies at a given torque (checked October 14, 2026)
  7. Bolt Depot: Bolt grade markings and strength chart (checked October 14, 2026)

Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.