Bolt Torque Spec Chart (Metric, Class 8.8 / 10.9 / 12.9)

These torques come from a target preload, not a lookup: T = K·d·F, where F = 0.75 · proof strength · tensile stress area (75% of proof load) and K ≈ 0.20 for dry, as-received bolts. Because most of the torque is spent on friction, the value is friction-dominated — treat the chart as a guide and follow the joint's engineering spec.

Rows

Columns

Basis

ISO 898-1 / VDI 2230 (K·d·F model)

Reviewed

June 1, 2026

The nut factor K depends on lubrication and plating: ≈0.20 dry or as-received zinc-plated, dropping to ≈0.15 lubricated and ≈0.10 with anti-seize — so a lubed bolt needs roughly 15–25% less torque for the same clamp force. These values target 75% of proof load, a typical reusable-joint preload; permanent or critical joints are sometimes taken to 90% of proof. Never exceed the bolt's proof load — past it the fastener yields and the preload becomes unpredictable.

Dry tightening torque to 75% of proof load, by metric size and property class.

Size

Pitch (mm)

Stress area At (mm²)

8.8 torque (N·m)

10.9 torque (N·m)

12.9 torque (N·m)

0.8

14.2

6.38

8.83

10.3

20.1

10.9

17.6

1.25

36.6

26.4

36.5

42.6

M10

1.5

52.2

72.2

84.4

M12

1.75

84.3

126

147

M14

115

145

201

235

M16

157

226

312

365

M20

2.5

245

441

610

712

M24

353

761

1,050

1,230