M4 bolt torque specifications (8.8, 10.9, 12.9)
An M4 x 0.7 class 8.8 screw takes 27 in-lb (3.1 N·m) dry, and class 10.9 takes 39 in-lb (4.4 N·m). Both are for plain steel, dry threads (K 0.20) tightened to a clamp load of 75% of proof load.
Contents13 sections
Key takeaways
- Class 8.8 dry: 27 in-lb (3.1 N·m); class 10.9 dry: 39 in-lb (4.4 N·m).
- Zinc-plated 8.8 is 24 in-lb, about 10% below plain dry, because plated threads have a lower nut factor (K 0.18) 1.
- M4 x 0.5 fine carries about 12% more clamp load than M4 x 0.7 at the same torque basis.
- The torque roughly doubles from M4 to M5 and more than doubles from M3 to M4.
Quick facts
| Coarse thread | M4 x 0.7 (8.78 mm²) |
|---|---|
| Fine thread | M4 x 0.5 (9.8 mm²) |
| Wrench, ISO 4014/4017 | 7 mm |
| Wrench, DIN 931/933 | 7 mm (same) |
M4 bolt specifications
| Thread | Pitch | Tensile stress area |
|---|---|---|
| M4 x 0.7 (coarse) | 0.7 mm pitch | 8.8 mm² |
| M4 x 0.5 (fine) | 0.5 mm pitch | 9.8 mm² |
| Wrench, ISO 4014/4017 | 7 mm1 | |
Stress areas from ISO 898-1 Table 42.
M4 torque by grade
| Grade | Plain, dry K 0.201 | Lubricated K 0.151 | Clamp load |
|---|---|---|---|
| Class 4.6 | 10 in-lb1.2 N·m | 8 in-lb0.9 N·m | 1.5 kN |
| Class 8.8 | 27 in-lb3.1 N·m | 20 in-lb2.3 N·m | 3.8 kN |
| Class 10.9 | 39 in-lb4.4 N·m | 29 in-lb3.3 N·m | 5.5 kN |
| Class 12.9 | 45 in-lb5.1 N·m | 34 in-lb3.8 N·m | 6.4 kN |
Calculated with T = K × D × F, where F is 75% of the bolt’s proof load1 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.
M4 4.6 torque
Proof 225 MPa · yield 240 MPa · tensile 400 MPa2. Clamp load at 75% of proof: 1.5 kN (M4 x 0.7).
| Condition | K | M4 x 0.7 | M4 x 0.5 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 10 in-lb1.2 N·m | 12 in-lb1.3 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 9 in-lb1.1 N·m | 11 in-lb1.2 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 8 in-lb0.9 N·m | 9 in-lb1.0 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 8 in-lb0.9 N·m | 9 in-lb1.1 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 6 in-lb0.7 N·m | 6 in-lb0.7 N·m |
M4 8.8 torque
Proof 580 MPa · yield 640 MPa · tensile 800 MPa2. Clamp load at 75% of proof: 3.8 kN (M4 x 0.7).
| Condition | K | M4 x 0.7 | M4 x 0.5 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 27 in-lb3.1 N·m | 30 in-lb3.4 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 24 in-lb2.7 N·m | 27 in-lb3.1 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 20 in-lb2.3 N·m | 23 in-lb2.6 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 22 in-lb2.4 N·m | 24 in-lb2.7 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 15 in-lb1.7 N·m | 17 in-lb1.9 N·m |
M4 10.9 torque
Proof 830 MPa · yield 940 MPa · tensile 1040 MPa2. Clamp load at 75% of proof: 5.5 kN (M4 x 0.7).
| Condition | K | M4 x 0.7 | M4 x 0.5 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 39 in-lb4.4 N·m | 43 in-lb4.9 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 35 in-lb3.9 N·m | 39 in-lb4.4 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 29 in-lb3.3 N·m | 32 in-lb3.7 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 31 in-lb3.5 N·m | 35 in-lb3.9 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 21 in-lb2.4 N·m | 24 in-lb2.7 N·m |
M4 12.9 torque
Proof 970 MPa · yield 1100 MPa · tensile 1220 MPa2. Clamp load at 75% of proof: 6.4 kN (M4 x 0.7).
| Condition | K | M4 x 0.7 | M4 x 0.5 |
|---|---|---|---|
| Plain steel, dryAs-received black or plain finish, clean threads, no lubricant | 0.201 | 45 in-lb5.1 N·m | 50 in-lb5.7 N·m |
| Zinc-plated, dryClean zinc-plated threads, no added lubricant | 0.181 | 41 in-lb4.6 N·m | 45 in-lb5.1 N·m |
| Lubricated (oil or grease)Light oil or grease on the threads and under the nut or head | 0.151 | 34 in-lb3.8 N·m | 38 in-lb4.3 N·m |
| Copper or metal-free anti-seizeLoctite C5-A copper or N-7000 metal-free anti-seize | 0.164 | 36 in-lb4.1 N·m | 40 in-lb4.6 N·m |
| Moly pasteMolybdenum disulfide paste | 0.115 | 25 in-lb2.8 N·m | 28 in-lb3.1 N·m |
Coarse or fine pitch
M4 x 0.7 is the coarse thread used in the tables, with a stress area of 8.78 mm² 2. The fine pitch, M4 x 0.5, comes from the ISO 262 selected-sizes table 6 and has 9.8 mm², about 12% more. In class 8.8 the fine thread clamps 4.3 kN against 3.8 kN for the coarse one, and its dry torque rises from 27 to 30 in-lb. The two values are close enough that mixing them up does little harm; mixing up the screw size does.
Where M4 sits between M3 and M5
Class 8.8 dry torque steps from 12 in-lb at M3 to 27 in-lb at M4 and 55 in-lb at M5. Each step is two times or more, because the short-form torque grows with diameter times stress area. The clamp load in 8.8 at M4 is 3.8 kN, about 860 lbf; in 10.9 it is 5.5 kN, about 1,230 lbf.
All of these M4 values are well under 10 ft-lb, so they are given in in-lb. Class 12.9 dry, the highest in the chart, is 45 in-lb (5.1 N·m), or 3.8 ft-lb.
Wrench size
Hex-head M4 bolts take a 7 mm wrench in both ISO 4014/4017 and the older DIN 931/933 1, so there is no ISO/DIN mix-up at this size.
Which class you have
Look for the class number on the head: ISO 898-1 calls for the property class symbol and the maker’s identification mark 2. The bolt grades page shows the markings. Class 10.9 has a proof stress of 830 MPa against 580 MPa for 8.8 2, so the 10.9 torque is about 43% higher at every condition. Class 4.6, the lowest class in the table, is only 10 in-lb (1.2 N·m) dry.
When the chart does not apply
The dry row is for plain, as-received steel. Zinc-plated M4 screws use K 0.18 1, which gives 24 in-lb (2.7 N·m) for 8.8, and oiled threads use K 0.15 1 for 20 in-lb (2.3 N·m). Applying the plain dry 27 in-lb to an oiled M4 would give about a third more clamp load than intended. See dry vs lubricated torque. If the equipment maker lists a torque for the screw, use theirs.
Sources
- 1
- 2
- 3
- 4
- 5Henkel Corporation (LOCTITE), LOCTITE LB 8012 Moly Paste TDS, April 2015Checked 21 Oct 2026
- 6Wikipedia, Wikipedia: ISO metric screw thread (ISO 262 selected sizes table)Checked 21 Oct 2026
Spotted a value that doesn’t match its source? Report an error
Related
- M3M3 x 0.5 screw torque: 12 in-lb (1.3 N·m) for class 8.8 and 17 in-lb (1.9 N·m) for 10.9 dry, plus 12.9, fine pitch, zinc and oiled values.
- M5M5 x 0.8 bolt torque: 55 in-lb (6.2 N·m) for class 8.8 and 78 in-lb (8.8 N·m) for 10.9 dry, plus 12.9, M5 x 0.5 fine, oiled and moly paste.
- 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.