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Bolt Torque Chart
Quick answer: A 1/2-13 Grade 5 bolt takes about 75 lb-ft clean and dry. Grade 2 is roughly half that, Grade 8 about 40% more. Lubricated bolts take about 25% less torque — the oil cuts friction, so the same torque overstretches the bolt.
Dry and lubricated torque values for Grade 2, 5 and 8 fasteners in both lb-ft and newton-metres, how to identify a grade from the head marking, and when a chart is the wrong tool.
Bolt torque chart (dry, plain finish)
Torque is a proxy. What actually holds a joint together is clamping force — the tension stretched into the bolt. Torque is simply the most practical way to get there in the field, which is why lubrication, plating and thread condition change the number so much.
| Size | Grade 2 (lb-ft) | Grade 5 (lb-ft) | Grade 8 (lb-ft) | Gr 5 lubricated | Gr 5 (N·m) |
|---|---|---|---|---|---|
| 1/4-20 | 4 | 8 | 12 | 6 | 11 |
| 1/4-28 | 5 | 10 | 14 | 8 | 14 |
| 5/16-18 | 9 | 17 | 24 | 13 | 23 |
| 5/16-24 | 10 | 19 | 27 | 14 | 26 |
| 3/8-16 | 15 | 30 | 45 | 22 | 41 |
| 3/8-24 | 17 | 35 | 50 | 26 | 47 |
| 7/16-14 | 24 | 50 | 70 | 38 | 68 |
| 7/16-20 | 27 | 55 | 78 | 41 | 75 |
| 1/2-13 | 37 | 75 | 105 | 56 | 102 |
| 1/2-20 | 41 | 85 | 120 | 64 | 115 |
| 9/16-12 | 53 | 110 | 155 | 82 | 149 |
| 5/8-11 | 73 | 150 | 210 | 112 | 203 |
| 3/4-10 | 125 | 265 | 375 | 199 | 359 |
| 7/8-9 | 129 | 420 | 605 | 315 | 570 |
| 1-8 | 188 | 640 | 910 | 480 | 868 |
Values are for clean, dry, plain-finish fasteners at roughly 75% of proof load. The lubricated column applies a 0.75 factor — oil, anti-seize and zinc plating all cut friction, so the same torque produces more tension and can snap the bolt.
Identifying the grade
| Grade | Head marking | Tensile strength | Typical use |
|---|---|---|---|
| Grade 2 | No marks | 74,000 psi (to 3/4″) | Low-stress general assembly |
| Grade 5 | Three radial lines | 120,000 psi | Automotive, machinery, most structural |
| Grade 8 | Six radial lines | 150,000 psi | Suspension, high-stress connections |
| Class 8.8 | “8.8” stamped | ~120,000 psi | Metric equivalent of Grade 5 |
| Class 10.9 | “10.9” stamped | ~150,000 psi | Metric equivalent of Grade 8 |
| 18-8 stainless | Often “18-8” or nothing | ~70,000–90,000 psi | Corrosion resistance, not strength |
Stainless is the trap. It looks premium and costs more, but 18-8 stainless is weaker than Grade 5 and prone to galling. Use it where corrosion is the problem, not where load is.
Where torque figures come from
The working relation is T = K × D × F, where T is torque, D is nominal bolt diameter, F is the target clamp load, and K is a friction coefficient — about 0.20 dry, 0.15 lubricated, 0.10 with a good anti-seize. Because K sits as a multiplier, a change in thread condition scales the whole result.
The clamp load target is normally 75% of the bolt’s proof load. That leaves margin below yield while putting enough tension in the joint to stop it working loose.
When not to use a chart
- The manufacturer gave a spec. Their number accounts for the joint materials, gasket compression and thread condition. It wins.
- Soft or brittle materials. Bolting into aluminium, plastic or cast iron, the material fails long before the bolt does. Torque to the material, not the fastener.
- Torque-to-yield bolts. Common in engines. They are torqued to a value then turned a further specified angle, and are single-use.
- Structural steel connections. Governed by RCSC procedures — turn-of-nut, tension-indicating washers or calibrated wrenches, not a generic chart.
Frequently asked questions
How much torque for a 1/2-13 bolt?
About 75 lb-ft for a Grade 5 bolt, clean and dry. Grade 2 takes roughly 37 lb-ft and Grade 8 about 105 lb-ft. Lubricated, reduce the Grade 5 figure to around 56 lb-ft.
How do I know what grade a bolt is?
Look at the head. No marks means Grade 2, three radial lines means Grade 5, six radial lines means Grade 8. Metric bolts carry a stamped number instead — 8.8 is roughly equivalent to Grade 5 and 10.9 to Grade 8.
Should I torque bolts dry or lubricated?
Match whatever the torque spec assumes. Standard charts including this one are dry values. Applying a dry figure to a lubricated bolt over-tightens it by about 25 to 30% because the oil cuts thread friction, so the same torque puts far more tension in the bolt.
Is stainless steel stronger than Grade 5?
No. Common 18-8 stainless runs around 70,000 to 90,000 psi tensile against 120,000 psi for Grade 5. Stainless is chosen for corrosion resistance, not strength, and it galls readily under torque.