Metric Bolt Torque Chart, ISO 898-1 Classes 8.8, 10.9 and 12.9 (M3 to M36)
Published . Last checked . Part of the bolt torque chart set; for any other size, friction or preload use the bolt torque calculator.
Most metric torque charts print one torque per size and class and leave you to guess the friction behind it. This one shows three. Two use the short form T = K F d, where T is the torque, K the nut factor, F the preload and d the nominal diameter. They take K = 0.20 for dry or zinc-plated steel as received and K = 0.15 for lightly oiled parts. The third is the VDI 2230 thread-geometry torque with thread and bearing friction of 0.12. The spread between the columns is the real uncertainty in a torque value, so pick the column that matches your parts, not the smallest number.
Every value is computed from ISO 898-1:2013. The stress area comes from the thread formula As = π/4 × ((d2 + d3)/2)², where d2 is the pitch diameter and d3 the minor diameter of the bolt thread. It reproduces the rounded ISO 898-1 Table 4 values within 0.4 %. Proof stresses are from ISO 898-1 Table 3: 830 MPa for 10.9 and 970 MPa for 12.9. Class 8.8 is 580 MPa up to M16 and 600 MPa above, which is the step you see between M16 and M18.
Because As comes from the formula rather than the rounded Table 4 values, the proof loads can differ from ISO 898-1 Table 5 by up to about 0.4 %. For example, M12 class 10.9 is 69.9 kN here and 70.0 kN in the table, and M16 class 8.8 is 90.9 kN against 91.0 kN. The difference is well inside torque scatter. The M12 class 8.8 row is the worked example in the bolt torque calculator.
What the columns assume
| Column | Basis |
|---|---|
| Thread | ISO 261 coarse pitch. |
| As | Tensile stress area, π/4 × ((d2 + d3)/2)², mm², within 0.4 % of the rounded ISO 898-1 Table 4 values. |
| Proof load | Proof stress S_p × As (ISO 898-1:2013 Table 3). |
| Preload 75 % | 0.75 × proof load, a common target for reusable joints. |
| Torque K 0.20 and K 0.15 | T = K F d with the 75 % preload. |
| Torque VDI 2230, μ 0.12 | T = F (0.16 P + 0.58 d2 μ_th + D_km/2 μ_b), μ_th = μ_b = 0.12, ISO 4017 hex head washer face and ISO 273 fine clearance hole. |
| Calculate | Opens the calculator with that row loaded, so you can change the friction, preload or hole. |
Torque chart, ISO 898-1 classes 8.8, 10.9 and 12.9
| Thread | Class | Torque K 0.20 (N·m) | Torque K 0.15 (N·m) | Torque VDI 2230, μ 0.12 (N·m) | Preload 75 % (kN) | As (mm²) | Proof stress (MPa) | Proof load (kN) | Calculator |
|---|---|---|---|---|---|---|---|---|---|
| M3 × 0.5 | 8.8 | 1.31 | 0.98 | 1.09 | 2.2 | 5.0 | 580 | 2.9 | Calculate |
| M3 × 0.5 | 10.9 | 1.88 | 1.41 | 1.57 | 3.1 | 5.0 | 830 | 4.2 | Calculate |
| M3 × 0.5 | 12.9 | 2.20 | 1.65 | 1.83 | 3.7 | 5.0 | 970 | 4.9 | Calculate |
| M4 × 0.7 | 8.8 | 3.05 | 2.29 | 2.54 | 3.8 | 8.8 | 580 | 5.1 | Calculate |
| M4 × 0.7 | 10.9 | 4.37 | 3.28 | 3.63 | 5.5 | 8.8 | 830 | 7.3 | Calculate |
| M4 × 0.7 | 12.9 | 5.11 | 3.83 | 4.25 | 6.4 | 8.8 | 970 | 8.5 | Calculate |
| M5 × 0.8 | 8.8 | 6.17 | 4.63 | 4.97 | 6.2 | 14.2 | 580 | 8.2 | Calculate |
| M5 × 0.8 | 10.9 | 8.83 | 6.62 | 7.11 | 8.8 | 14.2 | 830 | 11.8 | Calculate |
| M5 × 0.8 | 12.9 | 10.3 | 7.74 | 8.31 | 10.3 | 14.2 | 970 | 13.8 | Calculate |
| M6 × 1 | 8.8 | 10.5 | 7.88 | 8.68 | 8.8 | 20.1 | 580 | 11.7 | Calculate |
| M6 × 1 | 10.9 | 15.0 | 11.3 | 12.4 | 12.5 | 20.1 | 830 | 16.7 | Calculate |
| M6 × 1 | 12.9 | 17.6 | 13.2 | 14.5 | 14.6 | 20.1 | 970 | 19.5 | Calculate |
| M8 × 1.25 | 8.8 | 25.5 | 19.1 | 20.7 | 15.9 | 36.6 | 580 | 21.2 | Calculate |
| M8 × 1.25 | 10.9 | 36.5 | 27.3 | 29.6 | 22.8 | 36.6 | 830 | 30.4 | Calculate |
| M8 × 1.25 | 12.9 | 42.6 | 32.0 | 34.6 | 26.6 | 36.6 | 970 | 35.5 | Calculate |
| M10 × 1.5 | 8.8 | 50.5 | 37.8 | 40.9 | 25.2 | 58.0 | 580 | 33.6 | Calculate |
| M10 × 1.5 | 10.9 | 72.2 | 54.1 | 58.5 | 36.1 | 58.0 | 830 | 48.1 | Calculate |
| M10 × 1.5 | 12.9 | 84.4 | 63.3 | 68.4 | 42.2 | 58.0 | 970 | 56.2 | Calculate |
| M12 × 1.75 | 8.8 | 88.0 | 66.0 | 70.5 | 36.7 | 84.3 | 580 | 48.9 | Calculate |
| M12 × 1.75 | 10.9 | 125.9 | 94.4 | 100.9 | 52.5 | 84.3 | 830 | 69.9 | Calculate |
| M12 × 1.75 | 12.9 | 147.1 | 110.3 | 118.0 | 61.3 | 84.3 | 970 | 81.7 | Calculate |
| M14 × 2 | 8.8 | 140.6 | 105.5 | 112.6 | 50.2 | 115.4 | 580 | 67.0 | Calculate |
| M14 × 2 | 10.9 | 201.2 | 150.9 | 161.1 | 71.9 | 115.4 | 830 | 95.8 | Calculate |
| M14 × 2 | 12.9 | 235.1 | 176.4 | 188.3 | 84.0 | 115.4 | 970 | 112.0 | Calculate |
| M16 × 2 | 8.8 | 218.1 | 163.6 | 172.3 | 68.2 | 156.7 | 580 | 90.9 | Calculate |
| M16 × 2 | 10.9 | 312.1 | 234.1 | 246.6 | 97.5 | 156.7 | 830 | 130.0 | Calculate |
| M16 × 2 | 12.9 | 364.7 | 273.5 | 288.2 | 114.0 | 156.7 | 970 | 152.0 | Calculate |
| M18 × 2.5 | 8.8 | 311.8 | 233.9 | 248.5 | 86.6 | 192.5 | 600 | 115.5 | Calculate |
| M18 × 2.5 | 10.9 | 431.3 | 323.5 | 343.7 | 119.8 | 192.5 | 830 | 159.8 | Calculate |
| M18 × 2.5 | 12.9 | 504.1 | 378.1 | 401.7 | 140.0 | 192.5 | 970 | 186.7 | Calculate |
| M20 × 2.5 | 8.8 | 440.6 | 330.5 | 347.5 | 110.2 | 244.8 | 600 | 146.9 | Calculate |
| M20 × 2.5 | 10.9 | 609.5 | 457.2 | 480.8 | 152.4 | 244.8 | 830 | 203.2 | Calculate |
| M20 × 2.5 | 12.9 | 712.4 | 534.3 | 561.9 | 178.1 | 244.8 | 970 | 237.5 | Calculate |
| M22 × 2.5 | 8.8 | 600.7 | 450.5 | 472.3 | 136.5 | 303.4 | 600 | 182.0 | Calculate |
| M22 × 2.5 | 10.9 | 831.0 | 623.3 | 653.3 | 188.9 | 303.4 | 830 | 251.8 | Calculate |
| M22 × 2.5 | 12.9 | 971.2 | 728.4 | 763.5 | 220.7 | 303.4 | 970 | 294.3 | Calculate |
| M24 × 3 | 8.8 | 761.4 | 571.1 | 598.5 | 158.6 | 352.5 | 600 | 211.5 | Calculate |
| M24 × 3 | 10.9 | 1053.3 | 790.0 | 827.9 | 219.4 | 352.5 | 830 | 292.6 | Calculate |
| M24 × 3 | 12.9 | 1230.9 | 923.2 | 967.5 | 256.4 | 352.5 | 970 | 341.9 | Calculate |
| M27 × 3 | 8.8 | 1116.4 | 837.3 | 869.0 | 206.7 | 459.4 | 600 | 275.6 | Calculate |
| M27 × 3 | 10.9 | 1544.3 | 1158.2 | 1202.1 | 286.0 | 459.4 | 830 | 381.3 | Calculate |
| M27 × 3 | 12.9 | 1804.8 | 1353.6 | 1404.9 | 334.2 | 459.4 | 970 | 445.6 | Calculate |
| M30 × 3.5 | 8.8 | 1513.6 | 1135.2 | 1186.6 | 252.3 | 560.6 | 600 | 336.4 | Calculate |
| M30 × 3.5 | 10.9 | 2093.8 | 1570.3 | 1641.5 | 349.0 | 560.6 | 830 | 465.3 | Calculate |
| M30 × 3.5 | 12.9 | 2447.0 | 1835.2 | 1918.3 | 407.8 | 560.6 | 970 | 543.8 | Calculate |
| M33 × 3.5 | 8.8 | 2059.9 | 1544.9 | 1596.9 | 312.1 | 693.6 | 600 | 416.1 | Calculate |
| M33 × 3.5 | 10.9 | 2849.5 | 2137.1 | 2209.0 | 431.7 | 693.6 | 830 | 575.6 | Calculate |
| M33 × 3.5 | 12.9 | 3330.1 | 2497.6 | 2581.6 | 504.6 | 693.6 | 970 | 672.7 | Calculate |
| M36 × 4 | 8.8 | 2646.2 | 1984.6 | 2061.0 | 367.5 | 816.7 | 600 | 490.0 | Calculate |
| M36 × 4 | 10.9 | 3660.6 | 2745.4 | 2851.0 | 508.4 | 816.7 | 830 | 677.9 | Calculate |
| M36 × 4 | 12.9 | 4278.0 | 3208.5 | 3331.9 | 594.2 | 816.7 | 970 | 792.2 | Calculate |
Source: ISO 898-1:2013, Table 3 (proof stress) and the stress area formula of ISO 898-1; Tables 4 and 5 agree within about 0.4 %; VDI 2230 Part 1:2015 for the thread-geometry torque. Torque values are estimates; with a torque wrench the preload typically scatters by ±25 %.
Notes
- No joint stiffness or external load is considered. The chart sets the assembly preload only.
- K 0.20 and μ 0.12 are not the same friction: K 0.20 corresponds to μ of about 0.16 on a coarse thread, so the VDI 2230 column is lower.
- Stainless A2-70 and A4-80, fine pitches and other preload targets are in the calculator.
- For inch fasteners see the SAE J429 chart; for structural bolts the ASTM F3125 chart.