M24 bolt torque

An M24 x 3 bolt takes 762 N·m in class 8.8, 1,055 in 10.9 and 1,233 in 12.9, dry, at 75% of proof load (562, 778 and 909 ft-lb). Fine pitches take a little more. Oiled threads take a quarter less.

Sources checked

Torque at 75% of proof load.

Units
ThreadClassDryK 0.20Zinc platedK 0.20OiledK 0.15WaxedK 0.10Clamp load
M24 x 3coarseClass 4.621128621128615821410514313,392 lbf59.6 kN
Class 8.856276256276242257228138135,711 lbf158.8 kN
Class 10.97781,0557781,05558379138952749,400 lbf219.7 kN
Class 12.99091,2339091,23368292545561657,733 lbf256.8 kN
M24 x 2fineClass 4.622931122931117223311515614,568 lbf64.8 kN
Class 8.861282961282945962230641538,847 lbf172.8 kN
Class 10.98461,1478461,14763586142357453,738 lbf239.0 kN
Class 12.99891,3419891,3417421,00649567062,803 lbf279.4 kN

Work out M24 torque

Change grade, threads or preload

Bolt standard

As received, nothing added. K 0.20 (Portland Bolt, Fastenal).

% of proof load

The published charts use 75%.

M24 x 3 Class 8.8, dry, plain steel

562ft-lb762N·m

020040060080004008001200ft-lbN·m
Clamp load
35,711 lbf (158.8 kN)
Proof load
211.8 kN

The working

  1. Tensile stress area. A = π/4 × (d − 0.9382 × P)² = π/4 × (24 − 0.9382 × 3)² = 353 mm²
  2. Proof load. Class 8.8 proof stress is 600 MPa, so A × stress = 211,800 N.
  3. Clamp load. 75% of proof load = 158,850 N.
  4. Torque. T = K × D × F = 0.2 × 24 mm × 158.85 kN = 762 N·m (562 ft-lb).

Where the M24 x 3 numbers come from

The M24 x 3 coarse thread has a tensile stress area of 353 mm². A Class 10.9 bolt’s proof stress is 830 MPa, so its proof load is 292,990 N, and 75% of that is a clamp load of 219,743 N.

Torque = K × D × F = 0.20 × 24 mm × 219.74 kN = 1,055 N·m (778 ft-lb) dry. With oil (K 0.15) it’s 791 N·m (583 ft-lb).

Other sizes

All sizes on one page: the metric bolt torque chart.

Questions

What torque for an M24 x 3 Class 10.9 bolt?

1,055 N·m (778 ft-lb) dry and 791 N·m (583 ft-lb) oiled, at 75% of proof load. That clamps the joint with 49,400 lbf (219.7 kN).

What torque for an M24 x 3 Class 8.8 bolt?

762 N·m (562 ft-lb) dry, at 75% of proof load; a quarter less with oiled threads.

Coarse or fine thread?

Use whichever the bolt has. The fine M24 x 2 thread has a bigger stress area than the coarse one, so it takes slightly more torque for the same clamp. A thread gauge settles it.

Does this apply to wheel nuts or engine bolts?

No. Use the vehicle maker’s value for those: see lug nut torque by vehicle. These numbers are for general-purpose steel bolts where no spec exists.

Sources

  1. Fastenal: Mechanical properties per ISO 898-1 (externally threaded fasteners): proof stress by property class (checked October 14, 2026)
  2. Engineering Toolbox: Metric bolts: minimum ultimate tensile and proof loads, with ISO 898-1 stress areas (checked October 14, 2026)
  3. Engineering Toolbox: ISO 724 metric threads: coarse and fine pitches with tensile stress areas (checked October 14, 2026)
  4. Engineering Toolbox: Threaded bolts: tensile stress area formulas for unified and ISO metric threads (checked October 14, 2026)
  5. Fastenal: Torque–tension relationship for metric fasteners, property classes 4.6, 8.8, 10.9 and 12.9 (checked October 14, 2026)
  6. Portland Bolt: Bolt torque chart: T = KDP at 75% of proof load, with K for plain, waxed and galvanized bolts (checked October 14, 2026)

Spotted a number that doesn’t match your manual or a source? Tell us; corrections are logged on the sources page.