Quick-reference torque values for M8 bolts across all property classes. Values shown for dry/plain steel, coarse thread. Click any card for full details including all surface conditions.
These values assume dry/plain steel (K = 0.20) and coarse thread. Oiled, zinc-plated, or lubricated bolts require different torque. See full details →
For a typical M8 class 8.8 bolt the dry figure is 25.5 N·m (18.8 ft·lbs). If the threads are oiled, drop to 19.1 N·m — using the dry number on an oiled bolt would push it about 34% past the intended clamp load. Class 10.9 takes 36.5 N·m, 43% more than 8.8, and the fine M8×1.0 thread raises the 8.8 figure to 27.3 N·m because its stress area is 7% larger.
M8 sits in the range used for automotive, machinery and general fabrication work. Class 8.8 is the default high-strength choice here, with 10.9 used for engine internals, suspension and anything with significant fatigue or shock load. Every figure on this page is within the range of a normal 3/8" or 1/2" drive click wrench, so the main source of error is friction, not the tool: going from dry to oiled threads changes the required torque by about a quarter, nearly as much as stepping from class 8.8 to 10.9.
N·m. Coarse thread unless noted. Clamp load is the 75%-of-proof preload the torque is sized to produce.
| Coarse thread | M8×1.25 |
| Fine thread | M8×1.0 |
| Stress area (coarse / fine) | 36.61 / 39.17 mm² |
| Hex wrench size | 13 mm (ISO 4032) |
| Tap drill (coarse / fine) | 6.75 mm / 7 mm |
| Clearance hole (ISO 273 medium) | 9 mm |
Pitches per ISO 261/262; stress area per ISO 898-1; tap drill = nominal diameter minus pitch. M8 coarse vs fine →