Technically reviewed by Vincent, Founder at HEXVARO
Last reviewed
Quick answer
Quick answer: common bolt torque values
An M12 grade 8.8 bolt takes about 88 Nm dry. An M16 grade 8.8 bolt takes about 218 Nm, and an M20 grade 10.9 bolt about 610 Nm. These are calculated starting values for plain or zinc plated threads, not limits for a specific joint.
| Size | Grade 8.8 (Nm) | Grade 10.9 (Nm) | Grade 12.9 (Nm) | Inquiry |
|---|---|---|---|---|
| M8 | 25 | 36 | 43 | Quote this size |
| M10 | 50 | 72 | 84 | Quote this size |
| M12 | 88 | 126 | 147 | Quote this size |
| M16 | 218 | 312 | 365 | Quote this size |
| M20 | 441 | 610 | 712 | Quote this size |
| M24 | 761 | 1,053 | 1,231 | Quote this size |
Sourcing these sizes? DIN 933 full-thread hex bolts Hex bolt supplier
Bolt torque calculator
Choose the size, grade and thread condition to get proof load, preload and tightening torque.
- Torque (Nm)
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- Torque (lb-ft)
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- Preload
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- Proof load
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Metric bolt torque chart (Nm)
Coarse thread, K = 0.20, target preload 75 % of proof load. Values are rounded to the nearest whole Nm.
| Size | Stress area (mm²) | Grade 8.8 (Nm) | Grade 10.9 (Nm) | Grade 12.9 (Nm) | Inquiry |
|---|---|---|---|---|---|
| M6 | 20.1 | 11 | 15 | 18 | Quote this size |
| M8 | 36.6 | 25 | 36 | 43 | Quote this size |
| M10 | 58.0 | 50 | 72 | 84 | Quote this size |
| M12 | 84.3 | 88 | 126 | 147 | Quote this size |
| M14 | 115.4 | 141 | 201 | 235 | Quote this size |
| M16 | 156.7 | 218 | 312 | 365 | Quote this size |
| M18 | 192.5 | 312 | 431 | 504 | Quote this size |
| M20 | 244.8 | 441 | 610 | 712 | Quote this size |
| M22 | 303.4 | 601 | 831 | 971 | Quote this size |
| M24 | 352.5 | 761 | 1,053 | 1,231 | Quote this size |
| M27 | 459.4 | 1,116 | 1,544 | 1,805 | Quote this size |
| M30 | 560.6 | 1,514 | 2,094 | 2,447 | Quote this size |
| M33 | 693.6 | 2,060 | 2,849 | 3,330 | Quote this size |
| M36 | 816.7 | 2,646 | 3,661 | 4,278 | Quote this size |
How these torque values are calculated
Torque comes from the short formula T = K × F × d. T is torque, K is the nut factor, F is the target preload and d is the nominal diameter.
Worked example for M12 grade 8.8: the stress area is 84.3 mm² and the proof stress is 580 MPa, so proof load is 48.9 kN. Preload at 75 % is 36.7 kN. Torque is 0.20 × 36.7 kN × 12 mm = 88 Nm.
Proof stress follows ISO 898-1: 580 MPa for class 8.8 up to M16, 600 MPa for class 8.8 above M16, 830 MPa for class 10.9 and 970 MPa for class 12.9.
Target preload by size (kN)
Preload is the clamp force the joint actually needs. These figures are 75 % of proof load, so they do not depend on the nut factor.
| Size | Grade 8.8 (kN) | Grade 10.9 (kN) | Grade 12.9 (kN) | Inquiry |
|---|---|---|---|---|
| M6 | 8.8 | 12.5 | 14.6 | Quote this size |
| M8 | 15.9 | 22.8 | 26.6 | Quote this size |
| M10 | 25.2 | 36.1 | 42.2 | Quote this size |
| M12 | 36.7 | 52.5 | 61.3 | Quote this size |
| M14 | 50.2 | 71.9 | 84.0 | Quote this size |
| M16 | 68.2 | 97.5 | 114.0 | Quote this size |
| M18 | 86.6 | 119.8 | 140.0 | Quote this size |
| M20 | 110.2 | 152.4 | 178.1 | Quote this size |
| M22 | 136.5 | 188.9 | 220.7 | Quote this size |
| M24 | 158.6 | 219.4 | 256.4 | Quote this size |
| M27 | 206.7 | 286.0 | 334.2 | Quote this size |
| M30 | 252.3 | 349.0 | 407.8 | Quote this size |
| M33 | 312.1 | 431.7 | 504.6 | Quote this size |
| M36 | 367.5 | 508.4 | 594.2 | Quote this size |
How finish and lubrication change torque
The same torque gives very different preload on a slippery thread and a dry one. Multiply the chart value by the factor for your condition, or measure K on real parts for critical joints.
- Clean, dry plain or zinc plated thread: chart value (K about 0.20).
- Hot-dip galvanized: multiply by about 1.25 (K about 0.25).
- Lightly oiled thread: multiply by about 0.75 (K about 0.15).
- Copper anti-seize or MoS2 paste: multiply by about 0.65 (K about 0.13).
- Zinc flake or PTFE coating: ask the coating supplier for the friction value.
When not to use a general torque chart
Use the torque or tightening method in the design documents for structural, lifting, pressure and safety-critical joints. Structural bolting standards often set their own method, such as turn-of-nut. Torque tools also scatter, so a torque value does not guarantee an exact preload.
What to state in a bolt RFQ
- Standard, size, length and property class, for example DIN 933 M12 × 60 class 8.8.
- Finish, and any friction coefficient range your assembly process needs.
- Mating nut class and washer, which must suit the bolt grade.
- Quantity per size. MOQ is 500 pcs per specification.
Order these sizes from HEXVARO
Send your size list with grade, finish and quantity — we reply within 2 working hours with price, lead time and shipping terms.
- Reply: within 2 working hours
- MOQ: 500 pcs per specification
- Lead time: 10–15 days stock items
- Payment: T/T · L/C · PayPal
- Shipping ports: Tianjin · Ningbo · Shanghai · Shenzhen
- Incoterms: EXW · FOB · CFR · CIF · DAP
- Experience: Founder with 10+ years in the fastener industry
Frequently asked questions
What is the torque for an M12 8.8 bolt?
About 88 Nm with dry threads, using K = 0.20 and a preload of 75 % of proof load.
What is the torque for an M16 8.8 bolt?
About 218 Nm with dry threads. A grade 10.9 bolt of the same size takes about 312 Nm.
What is the torque for an M10 10.9 bolt?
About 72 Nm with dry threads.
Should lubricated bolts get less torque?
Yes. Lubrication lowers friction, so the same torque creates more preload. Reduce the torque, often to about 65 to 75 % of the dry value.
Does this chart apply to stainless steel bolts?
No. A2 and A4 fasteners have different strength and friction values, so use a chart made for stainless steel.
How do I convert Nm to lb-ft?
Multiply Nm by 0.7376. For example, 88 Nm is about 65 lb-ft.
Does HEXVARO supply these bolts?
Yes. We supply hex bolts in grades 8.8, 10.9 and 12.9 with a MOQ of 500 pcs per specification. Send the size list for a quotation.
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