// Torque Calculator — size · class · lubrication
Coarse thread, new uncoated fastener, steel joint. Stainless values already assume µ ≈ 0.20 (MoS₂ option ≈ anti-seize). Classes 4.6/5.8 are derived from the 8.8 base by yield ratio (240/400 vs 640 MPa). Titanium Gr5: conservative guide equal to class 8.8 preload — always assemble with anti-seize. Brass: guide value ≈ 0.4× class 8.8 — verify on soft joints. Safety-critical joints: verify per VDI 2230 or the equipment manual.
Torque Chart — Coarse Thread, Classes 8.8 / 10.9 / 12.9
Values in newton-metres (Nm) for new, uncoated bolts with a steel nut or steel tapped hole, thread and head bearing surface lightly oiled (µtotal = 0.14), preload at 90% of yield per the VDI 2230 convention. If your bolts are lubricated or fully degreased, apply the correction factors below.
| Size | Class 8.8 | Class 10.9 | Class 12.9 |
|---|---|---|---|
| M3 | 1.3 12 in-lb | 2.0 18 in-lb | 2.3 20 in-lb |
| M4 | 2.9 26 in-lb | 4.3 38 in-lb | 5.0 44 in-lb |
| M5 | 5.8 51 in-lb | 8.4 74 in-lb | 9.9 88 in-lb |
| M6 | 9.9 88 in-lb | 14.5 11 ft-lb | 17 13 ft-lb |
| M8 | 24 18 ft-lb | 35 26 ft-lb | 41 30 ft-lb |
| M10 | 47 35 ft-lb | 69 51 ft-lb | 81 60 ft-lb |
| M12 | 81 60 ft-lb | 119 88 ft-lb | 139 103 ft-lb |
| M14 | 129 95 ft-lb | 190 140 ft-lb | 222 164 ft-lb |
| M16 | 198 146 ft-lb | 291 215 ft-lb | 341 252 ft-lb |
| M18 | 283 209 ft-lb | 402 296 ft-lb | 471 347 ft-lb |
| M20 | 402 296 ft-lb | 570 420 ft-lb | 667 492 ft-lb |
| M22 | 552 407 ft-lb | 783 578 ft-lb | 917 676 ft-lb |
| M24 | 691 510 ft-lb | 981 724 ft-lb | 1148 847 ft-lb |
| M27 | 1022 754 ft-lb | 1452 1071 ft-lb | 1700 1254 ft-lb |
| M30 | 1387 1023 ft-lb | 1969 1452 ft-lb | 2305 1700 ft-lb |
| M33 | 1884 1390 ft-lb | 2676 1974 ft-lb | 3132 2310 ft-lb |
| M36 | 2418 1783 ft-lb | 3435 2534 ft-lb | 4020 2965 ft-lb |
Where this chart stops applying — and what we machine instead
These figures assume a standard bolt with a full shank cross-section. Change the shank and the torque has to be recalculated on the section that actually carries the load, not on the thread. EKINSUN LTD is a custom parts manufacturer in Guangdong, China and makes those non-catalogue fasteners from one piece, quoted within 12 hours.
| Your case | Stocked? | How we make it |
|---|---|---|
| A standard bolt in a catalogue size and class | Yes, off the shelf | Buy it from a distributor — cheaper and faster than anything machined. Honest recommendation |
| Reduced or waisted shank, so the shank is thinner than the thread | Rare, a handful of sizes | Turned to drawing; torque referenced to the shank area, which is now the weakest section, not the thread stress area |
| Hollow or cross-drilled bolt | Only as a banjo bolt | Bore diameter free; the load-bearing area and its torque limit are stated in the quotation |
| A grip length that must land exactly, thread clear of the shear plane | Catalogues jump in 5 or 10 mm steps | Cut to the exact grip so the shank carries the shear — a thread across a shear plane is a different, lower rating |
| A fine pitch combination nobody lists | Common pitches only | Single-point cut to any pitch; the larger stress area raises the torque figure accordingly |
| Class 10.9 or 12.9 that also needs corrosion protection | Electroplated zinc is a risk | Zinc flake instead of electroplating, to avoid hydrogen embrittlement under ISO 4042 |
Reading the units: every cell carries the imperial equivalent under the N·m figure. Above 10 ft-lb that second line is in ft-lb; below it the value switches to in-lb, because that is the range US torque wrenches are actually graduated in — an M4 at 2.9 N·m is 26 in-lb, and a wrench asking for "2.1 ft-lb" is not a wrench you can set. Conversions used: 1 N·m = 0.7376 ft-lb = 8.851 in-lb.
Reading the classes: the first figure is tensile strength in hundreds of MPa, and the product of both figures is yield in tens of MPa — so 8.8 = 800 MPa tensile / 640 MPa yield, 10.9 = 1000/900, 12.9 = 1200/1080. Same size, higher class, higher preload, higher torque. If your bolt head carries no class marking, treat it as 4.6/5.8 commercial hardware and do not use this table's values.
Stainless Steel A2 / A4 Torque Chart (Classes 70 & 80)
Stainless bolts are weaker than 8.8 (class 70 yields ≈450 MPa) and gall easily, so they get their own table — commonly published for µtotal ≈ 0.20 with anti-seize recommended. A2 (≈304 chemistry) and A4 (≈316, marine) share the same property classes, so torque values are identical; only corrosion resistance differs.
| Size | Class 70 (A2-70 / A4-70) | Class 80 (A2-80 / A4-80) |
|---|---|---|
| M3 | 1.1 9.7 in-lb | 1.5 13 in-lb |
| M4 | 2.6 23 in-lb | 3.4 30 in-lb |
| M5 | 5.1 45 in-lb | 6.8 60 in-lb |
| M6 | 8.8 78 in-lb | 11.7 104 in-lb |
| M8 | 21 15 ft-lb | 29 21 ft-lb |
| M10 | 44 32 ft-lb | 58 43 ft-lb |
| M12 | 74 55 ft-lb | 99 73 ft-lb |
| M14 | 119 88 ft-lb | 158 117 ft-lb |
| M16 | 183 135 ft-lb | 244 180 ft-lb |
| M18 | 259 191 ft-lb | 345 254 ft-lb |
| M20 | 364 268 ft-lb | 485 358 ft-lb |
| M22 | 495 365 ft-lb | 660 487 ft-lb |
| M24 | 630 465 ft-lb | 840 620 ft-lb |
| M27 | 920 679 ft-lb | 1225 904 ft-lb |
| M30 | 1246 919 ft-lb | 1660 1224 ft-lb |
Ordering stainless hardware in non-catalog dimensions? We machine custom stainless bolts in A2/304 and A4/316 to drawing, from single pieces.
Fine Pitch Torque Chart
Fine threads have a larger tensile stress area than coarse threads of the same nominal size, so preload and torque run slightly higher. Don't approximate — use the dedicated values:
| Thread | Class 8.8 | Class 10.9 | Class 12.9 |
|---|---|---|---|
| M8 × 1 | 26 19 ft-lb | 38 28 ft-lb | 44 32 ft-lb |
| M10 × 1.25 | 49 36 ft-lb | 72 53 ft-lb | 84 62 ft-lb |
| M12 × 1.25 | 88 65 ft-lb | 129 95 ft-lb | 151 111 ft-lb |
| M12 × 1.5 | 86 63 ft-lb | 126 93 ft-lb | 148 109 ft-lb |
| M14 × 1.5 | 138 102 ft-lb | 203 150 ft-lb | 237 175 ft-lb |
| M16 × 1.5 | 210 155 ft-lb | 308 227 ft-lb | 360 266 ft-lb |
| M18 × 1.5 | 308 227 ft-lb | 438 323 ft-lb | 513 378 ft-lb |
| M20 × 1.5 | 431 318 ft-lb | 615 454 ft-lb | 719 530 ft-lb |
| M22 × 1.5 | 580 428 ft-lb | 826 609 ft-lb | 966 712 ft-lb |
| M24 × 2 | 731 539 ft-lb | 1044 770 ft-lb | 1221 901 ft-lb |
Dry vs Lubricated: the Correction Most Charts Skip
Tightening torque mostly fights friction — only a small share becomes bolt tension. Change the friction and the "right" torque changes with it, which is why quoting one number per size without stating the thread condition is meaningless:
- Lightly oiled, as-delivered (µ ≈ 0.14): use the table values above — this is the standard assumption.
- MoS₂ paste, assembly grease, wax (µ ≈ 0.10): multiply by ≈0.82. Applying dry-table torque to well-lubricated threads can stretch the bolt past yield.
- Degreased, bone-dry threads (µ ≈ 0.20): multiply by ≈1.25 to reach the same preload.
- Threads into aluminum (6061, 7075): the tapped hole strips before the bolt fails — cut torque substantially, use ≥1.5–2×d engagement, or fit a threaded insert. Details in our stainless-in-aluminum guide.
Quick Answers by Size
M5 bolt torque
Coarse M5: 5.8 Nm · 51 in-lb (8.8), 8.4 Nm · 74 in-lb (10.9), 9.9 Nm · 88 in-lb (12.9); stainless A2/A4-70 ≈ 5.1 Nm. Small screws are torn off easily by power tools — use a torque-limiting driver near these values.
M6 bolt torque
Coarse M6: 9.9 Nm · 88 in-lb (8.8), 14.5 Nm · 11 ft-lb (10.9), 17 Nm · 13 ft-lb (12.9); A2/A4-70 ≈ 8.8 Nm. M6 into tapped aluminum housings is the classic stripped-thread case — drop the torque or spec an insert.
M8 bolt torque
Coarse M8: 24 Nm · 18 ft-lb (8.8), 35 Nm · 26 ft-lb (10.9), 41 Nm · 30 ft-lb (12.9); fine M8×1: 26/38/44 Nm (19/28/32 ft-lb); stainless 70/80: 21/29 Nm (15/21 ft-lb). The most-asked size on this chart — and the answer changes ±20% with lubrication, so check the thread condition first.
M10 bolt torque
Coarse M10: 47 Nm · 35 ft-lb (8.8), 69 Nm · 51 ft-lb (10.9), 81 Nm · 60 ft-lb (12.9); fine M10×1.25: 49/72/84 Nm (36/53/62 ft-lb); stainless 70/80: 44/58 Nm (32/43 ft-lb).
M12 bolt torque
Coarse M12: 81 Nm · 60 ft-lb (8.8), 119 Nm · 88 ft-lb (10.9), 139 Nm · 103 ft-lb (12.9). Automotive fine pitches are common here — M12×1.25 runs 88/129/151 Nm (65/95/111 ft-lb) and M12×1.5 runs 86/126/148 Nm (63/93/109 ft-lb).
M14 bolt torque
Coarse M14: 129 Nm · 95 ft-lb (8.8), 190 Nm · 140 ft-lb (10.9), 222 Nm · 164 ft-lb (12.9); M14×1.5: 138/203/237 Nm (102/150/175 ft-lb); stainless 70/80: 119/158 Nm (88/117 ft-lb).
M16 bolt torque
Coarse M16: 198 Nm · 146 ft-lb (8.8), 291 Nm · 215 ft-lb (10.9), 341 Nm · 252 ft-lb (12.9); M16×1.5: 210/308/360 Nm (155/227/266 ft-lb). From M16 up, verify with a calibrated wrench — hand feel is hopeless at these levels.
M18 bolt torque
Coarse M18: 283 Nm · 209 ft-lb (8.8), 402 Nm · 296 ft-lb (10.9), 471 Nm · 347 ft-lb (12.9); M18×1.5: 308/438/513 Nm (227/323/378 ft-lb).
M20 bolt torque
Coarse M20: 402 Nm · 296 ft-lb (8.8), 570 Nm · 420 ft-lb (10.9), 667 Nm · 492 ft-lb (12.9); stainless 70/80: 364/485 Nm (268/358 ft-lb). Structural M20 connections normally follow the joint spec (e.g. EN 1090 preloading), not a generic chart.
M24 bolt torque
Coarse M24: 691 Nm · 510 ft-lb (8.8), 981 Nm · 724 ft-lb (10.9), 1148 Nm · 847 ft-lb (12.9); M24×2: 731/1044/1221 Nm (539/770/901 ft-lb); stainless 70/80: 630/840 Nm (465/620 ft-lb). At this size, thread condition swings the number by hundreds of Nm — state it on the drawing. Large and oversize bolts beyond catalog ranges are our specialty: see large custom bolts.
When this chart doesn't apply: non-standard threads, oversize or repaired threads, special materials (titanium, brass), reused or coated bolts, and any safety-critical joint. Those need a per-joint calculation — and if the bolt itself can't be bought, we machine non-standard thread bolts and replacement bolts from a sample, from one piece, with the torque guidance included.
When this chart stops being enough: A torque figure is only valid while the bolt is the weakest thing in the joint. It stops being valid when: the female thread is in aluminium or a casting and will strip long before the bolt yields, so the bolt class is the wrong limit entirely; the bolt is stainless going into aluminium, where galling seizes the thread before the wrench reaches the number; the grade looks stronger than it is - A4-80 reads like a big number but its 800 MPa tensile is below a plain 8.8 above M16; the pitch is fine or non-standard, so the tension for a given torque is not what the coarse table says; or the fastener simply is not made in that length, hand or head. That last one is most of our work. We machine the part that the table cannot describe — special screws and bolts cut to your size, double-end studs with two different threads, or when the thread in the part is the thing that failed. From one piece, quoted within 12 hours.
Torque Chart FAQ
24 Nm / 18 ft-lb (8.8), 35 Nm / 26 ft-lb (10.9), 41 Nm / 30 ft-lb (12.9) — coarse thread, lightly oiled. Stainless A2/A4: 21 Nm / 15 ft-lb (70) or 29 Nm / 21 ft-lb (80).
18 ft-lb for class 8.8, 26 ft-lb for 10.9 and 30 ft-lb for 12.9 — coarse thread, lightly oiled. Every table on this page carries the ft-lb figure under the N·m value, so you never have to convert by hand. Below roughly 10 ft-lb the numbers are given in in-lb instead, because that is the range most US torque wrenches are actually graduated in: an M4 at 2.9 N·m reads 26 in-lb, not 2.1 ft-lb.
Multiply N·m by 0.7376 for ft-lb, or by 8.851 for in-lb. Going the other way, multiply ft-lb by 1.3558. A rough field check: ft-lb ≈ three quarters of the N·m figure.
Strength classes: first figure = tensile in hundreds of MPa, product of both = yield in tens of MPa. 8.8 → 800/640 MPa; 10.9 → 1000/900; 12.9 → 1200/1080.
Yes — with MoS₂ or assembly paste apply ≈0.82× the table value; degreased dry threads need ≈1.25×. Torque is mostly friction, so the thread condition decides the number.
No — A2/A4 class 70 is markedly weaker than 8.8 and galls without anti-seize. Use the dedicated stainless table above.
Slightly, yes: fine threads have a larger stress area — e.g. M12×1.25 takes 88 Nm (8.8) vs 81 Nm coarse. Use the fine-pitch table.
Tapped 6061/7075 strips before the bolt yields. Reduce torque substantially, use 1.5–2×d thread engagement, or spec a threaded insert. Drilling or tapping the hole yourself? See the metric clearance hole & tap drill chart.
Bolts tightened to these near-yield values may be reused only if the joint spec allows and they're undamaged; torque-to-yield and stretch bolts are single-use. When in doubt, replace — the bolt is the cheapest part of the joint.
Yes — download the free PDF with all three tables and the lubrication corrections. No email required.
Yes — A2/A4 class 70 yields around 450 MPa versus 640 MPa for 8.8, so torques are lower, and stainless galls easily so friction is higher and anti-seize is recommended. Use the dedicated A2/A4 table, not the carbon-steel one.
Fine-pitch threads have a larger stress area, so they carry slightly higher preload and torque — for example M12×1.25 at 88 Nm (8.8) versus 81 Nm for coarse M12. Use the fine-pitch table for fine threads rather than approximating from coarse values.
Standard tables assume a steel nut or steel tapped hole. Threads tapped directly into aluminum such as 6061 or 7075 strip long before the bolt yields — reduce torque substantially (often to roughly 60% or per joint calculation), increase engagement length to at least 1.5–2×d, or use a threaded insert.
Free PDF Chart
All three tables + lubrication factors on one printable sheet.
Download PDF ↓Bolt You Can't Buy?
Non-standard thread, oversize, obsolete or worn sample — we machine custom bolts from 1 piece. Send a drawing, sketch or photo.