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Minimum Breaking Torque Calculator
Calculate the minimum breaking torque (MB,min) for metric bolts and screws per ISO 898-7. This is the minimum torque required to cause bolt failure in a torsion test — used for incoming quality inspection and fastener qualification.
Calculator
Quick Reference — Minimum Breaking Torque (N·m)
| Size | 4.8 | 5.8 | 8.8 | 10.9 | 12.9 |
|---|---|---|---|---|---|
| M5 | 6.0 | 7.4 | 11.4 | 14.8 | 17.3 |
| M6 | 10.1 | 12.5 | 19.3 | 25.1 | 29.4 |
| M8 | 24.6 | 30.5 | 46.8 | 60.9 | 71.4 |
| M10 | 48.7 | 60.3 | 92.8 | 120.6 | 141.5 |
| M12 | 85.0 | 105.2 | 161.9 | 210.4 | 246.8 |
| M14 | 135.2 | 167.4 | 257.6 | 334.9 | 392.8 |
| M16 | 211.0 | 261.2 | 401.9 | 522.5 | 612.9 |
| M18 | 290.3 | 359.4 | 553.0 | 718.8 | 843.3 |
| M20 | 411.6 | 509.6 | 784.0 | 1019.2 | 1195.6 |
| M22 | 559.9 | 693.3 | 1066.6 | 1386.5 | 1626.5 |
| M24 | 711.6 | 881.1 | 1355.5 | 1762.2 | 2067.2 |
| M27 | 1041.0 | 1288.9 | 1982.9 | 2577.7 | 3023.9 |
| M30 | 1413.7 | 1750.3 | 2692.8 | 3500.6 | 4106.5 |
| M33 | 1923.8 | 2381.8 | 3664.3 | 4763.6 | 5588.1 |
| M36 | 2470.6 | 3058.8 | 4705.9 | 6117.7 | 7176.5 |
Formula & Standards
Minimum Breaking Torque: MB,min = K × Fm × d
Where:
- K = Nut factor (torque coefficient), typically 0.20 for standard test conditions (ISO 898-7)
- Fm = Rm × As — minimum tensile force (N)
- Rm = Minimum tensile strength of bolt material (MPa)
- As = Tensile stress area of bolt thread (mm²)
- d = Nominal bolt diameter (mm)
Reference: ISO 898-7 (Mechanical properties of fasteners — Torsional test and minimum torques for bolts and screws), ISO 898-1 (Bolts, screws and studs — Property classes). Values are theoretical minimums. Actual values may vary with surface treatment and lubrication.