M24 bolt torque specifications (8.8, 10.9, 12.9)
An M24 x 3 class 8.8 bolt takes 562 ft-lb (762 N·m) dry, and class 10.9 takes 778 ft-lb (1,055 N·m). Both are for plain steel, dry threads (K 0.20) tightened to a clamp load of 75% of proof load.
Contents14 sections
Key takeaways
- Class 8.8 dry: 562 ft-lb (762 N·m); class 10.9 dry: 778 ft-lb (1,055 N·m).
- Class 8.8 at M24 uses the over-16 mm proof stress of 600 MPa 1.
- M24 x 2 fine carries about 9% more clamp load than M24 x 3.
- An M24 class 8.8 takes about 13% less torque than a 1-8 Grade 5.
Quick facts
| Coarse thread | M24 x 3 (353 mm²) |
|---|---|
| Fine thread | M24 x 2 (384 mm²) |
| Wrench, ISO 4014/4017 | 36 mm |
| Wrench, DIN 931/933 | 36 mm (same) |
M24 bolt specifications
| Thread | Pitch | Tensile stress area |
|---|---|---|
| M24 x 3 (coarse) | 3 mm pitch | 353.0 mm² |
| M24 x 2 (fine) | 2 mm pitch | 384.0 mm² |
| Wrench, ISO 4014/4017 | 36 mm2 | |
Stress areas from ISO 898-1 Table 41.
M24 torque by grade
| Grade | Plain, dry K 0.202 | Lubricated K 0.152 | Clamp load |
|---|---|---|---|
| Class 4.6 | 211 ft-lb286 N·m | 158 ft-lb214 N·m | 59.6 kN |
| Class 8.8 | 562 ft-lb762 N·m | 422 ft-lb572 N·m | 158.9 kN |
| Class 10.9 | 778 ft-lb1,055 N·m | 583 ft-lb791 N·m | 219.7 kN |
| Class 12.9 | 909 ft-lb1,233 N·m | 682 ft-lb925 N·m | 256.8 kN |
Calculated with T = K × D × F, where F is 75% of the bolt’s proof load2 and K is the nut factor for each condition. Real preload from a torque wrench scatters by about ±25%3. When the equipment maker gives a torque, use theirs. How these numbers are made.
M24 4.6 torque
Proof 225 MPa · yield 240 MPa · tensile 400 MPa1. Clamp load at 75% of proof: 59.6 kN (M24 x 3).
| Condition | K | M24 x 3 | M24 x 2 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 211 ft-lb286 N·m | 229 ft-lb311 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 190 ft-lb257 N·m | 206 ft-lb280 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 158 ft-lb214 N·m | 172 ft-lb233 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 169 ft-lb229 N·m | 184 ft-lb249 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 116 ft-lb157 N·m | 126 ft-lb171 N·m |
M24 8.8 torque
Proof 600 MPa · yield 660 MPa · tensile 830 MPa1. Clamp load at 75% of proof: 158.9 kN (M24 x 3).
| Condition | K | M24 x 3 | M24 x 2 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 562 ft-lb762 N·m | 612 ft-lb829 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 506 ft-lb686 N·m | 551 ft-lb746 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 422 ft-lb572 N·m | 459 ft-lb622 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 450 ft-lb610 N·m | 489 ft-lb664 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 309 ft-lb419 N·m | 336 ft-lb456 N·m |
M24 10.9 torque
Proof 830 MPa · yield 940 MPa · tensile 1040 MPa1. Clamp load at 75% of proof: 219.7 kN (M24 x 3).
| Condition | K | M24 x 3 | M24 x 2 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 778 ft-lb1,055 N·m | 846 ft-lb1,147 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 700 ft-lb949 N·m | 762 ft-lb1,033 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 583 ft-lb791 N·m | 635 ft-lb861 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 622 ft-lb844 N·m | 677 ft-lb918 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 428 ft-lb580 N·m | 465 ft-lb631 N·m |
M24 12.9 torque
Proof 970 MPa · yield 1100 MPa · tensile 1220 MPa1. Clamp load at 75% of proof: 256.8 kN (M24 x 3).
| Condition | K | M24 x 3 | M24 x 2 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.202 | 909 ft-lb1,233 N·m | 989 ft-lb1,341 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.182 | 818 ft-lb1,109 N·m | 890 ft-lb1,207 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.152 | 682 ft-lb925 N·m | 742 ft-lb1,006 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 727 ft-lb986 N·m | 791 ft-lb1,073 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 500 ft-lb678 N·m | 544 ft-lb738 N·m |
Coarse or fine pitch
M24 x 3 coarse has 353 mm² of stress area 1; M24 x 2 fine has 384 mm² 2, about 8.8% more. In class 8.8 dry the fine thread takes 612 ft-lb instead of 562 ft-lb and clamps 172.8 kN instead of 158.8 kN.
Class 8.8 above and below M16
M24 is well into the upper class 8.8 band: 600 MPa proof stress and 830 MPa minimum tensile strength above 16 mm, against 580 and 800 MPa up to 16 mm 1. The clamp load at 75% of proof is 158.9 kN (about 35,710 lbf) in 8.8 and 219.7 kN (about 49,400 lbf) in 10.9. Class 10.9 is about 38% above 8.8 at this size, and 12.9 dry is 909 ft-lb (1,233 N·m).
From M20 to M24 the class 8.8 torque rises about 1.7 times; from M24 to M30 it doubles.
M24 next to 1 inch
M24 (24 mm) is smaller than 1 in (25.4 mm). On the same basis an M24 class 8.8 takes about 13% less torque than a 1-8 Grade 5 and clamps about 8% less. Using the 1 in figure on an M24 would push its clamp load to about 86% of proof instead of 75%.
Wrench size
M24 heads are 36 mm across the flats in both ISO 4014/4017 and DIN 931/933 2. One size down, M22 differs: 34 mm ISO, 32 mm DIN 2.
Which class you have
The class symbol and the maker’s mark are on the head 1; see the bolt grades page. A class 4.6 M24 takes only 211 ft-lb (286 N·m) dry, well under half the 8.8 value, so an unidentified bolt should not get the 8.8 figure.
When the chart does not apply
The chart uses 75% of proof load, Fastenal’s basis for standard bolts; Fastenal uses 90% for special applications such as structural bolts 2. On a 90% basis an M24 class 8.8 dry would be about 675 ft-lb, so do not mix the two kinds of table.
For structural joints, RCSC warns that the torque-to-pretension ratio can vary by as much as ±40% unless it is established for each bolt lot, diameter and surface condition 6; see structural bolts. On machinery, check what is on the threads: copper or metal-free anti-seize (K 0.16) 4 brings class 8.8 M24 down to 450 ft-lb, and oil (K 0.15) 2 to 422 ft-lb. See dry vs lubricated torque.
Sources
- 1
- 2
- 3
- 4
- 5Henkel Corporation (LOCTITE), LOCTITE LB 8012 Moly Paste TDS, April 2015Checked 21 Oct 2026
- 6
Spotted a value that doesn’t match its source? Report an error
Related
- M20M20 x 2.5 bolt torque: 325 ft-lb (441 N·m) for class 8.8 and 450 ft-lb (610 N·m) for 10.9 dry, plus 12.9, M20 x 1.5 fine, zinc and oiled values.
- M30M30 x 3.5 bolt torque: 1,117 ft-lb (1,515 N·m) for class 8.8 and 1,545 ft-lb (2,095 N·m) for 10.9 dry, plus 12.9, M30 x 2 fine and lubricated values.
- 1 in1-8 Grade 5 bolt torque is 644 ft-lb dry and Grade 8 is 909 ft-lb. Charts for 1-8 and 1-12 in Grade 2, 5 and 8, dry, zinc-plated and oiled.
- Class 8.8Class 8.8 bolt torque from M3 to M30, dry, zinc-plated and lubricated, with the ISO 898-1 proof stress step from 580 MPa to 600 MPa above M16.
- Class 10.9Class 10.9 bolt torque from M3 to M30, dry, zinc-plated and lubricated, with ISO 898-1 strength (830 MPa proof) and how it compares with 8.8 and 12.9.
- Bolt torque calculatorBolt torque calculator for SAE and metric bolts by size, thread, grade and lubrication, using T = K × D × F with the proof loads from SAE J429 and ISO 898-1.
- Dry vs lubricated torqueWhy oiled bolts need less torque than dry ones for the same clamp load, with nut factor K values from Fastenal, NASA and Henkel for oil, zinc, anti-seize and moly.
- StructuralA325 and A490 structural bolts under RCSC 2020: snug-tight, pretensioned and slip-critical joints, the five pretensioning methods, and why table torque is not used.