M36 bolt torque

An M36 x 4 bolt takes 2,647 N·m in class 8.8, 3,662 in 10.9 and 4,279 in 12.9, dry, at 75% of proof load (1952, 2701 and 3156 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
M36 x 4coarseClass 4.673299373299354974436649630,994 lbf137.9 kN
Class 8.81,9522,6471,9522,6471,4641,9859761,32482,651 lbf367.6 kN
Class 10.92,7013,6622,7013,6622,0262,7461,3501,831114,334 lbf508.6 kN
Class 12.93,1564,2793,1564,2792,3673,2101,5782,140133,619 lbf594.4 kN
M36 x 3fineClass 4.67751,0517751,05158178838852532,815 lbf146.0 kN
Class 8.82,0672,8032,0672,8031,5502,1021,0341,40187,507 lbf389.3 kN
Class 10.92,8593,8772,8593,8772,1452,9081,4301,938121,051 lbf538.5 kN
Class 12.93,3424,5313,3424,5312,5063,3981,6712,265141,469 lbf629.3 kN

Work out M36 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%.

M36 x 4 Class 8.8, dry, plain steel

1,952ft-lb2,647N·m

0100020000100020003000ft-lbN·m
Clamp load
82,651 lbf (367.6 kN)
Proof load
490.2 kN

The working

  1. Tensile stress area. A = π/4 × (d − 0.9382 × P)² = π/4 × (36 − 0.9382 × 4)² = 817 mm²
  2. Proof load. Class 8.8 proof stress is 600 MPa, so A × stress = 490,200 N.
  3. Clamp load. 75% of proof load = 367,650 N.
  4. Torque. T = K × D × F = 0.2 × 36 mm × 367.65 kN = 2,647 N·m (1,952 ft-lb).

Where the M36 x 4 numbers come from

The M36 x 4 coarse thread has a tensile stress area of 817 mm². A Class 10.9 bolt’s proof stress is 830 MPa, so its proof load is 678,110 N, and 75% of that is a clamp load of 508,583 N.

Torque = K × D × F = 0.20 × 36 mm × 508.58 kN = 3,662 N·m (2,701 ft-lb) dry. With oil (K 0.15) it’s 2,746 N·m (2,026 ft-lb).

Other sizes

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

Questions

What torque for an M36 x 4 Class 10.9 bolt?

3,662 N·m (2,701 ft-lb) dry and 2,746 N·m (2,026 ft-lb) oiled, at 75% of proof load. That clamps the joint with 114,334 lbf (508.6 kN).

What torque for an M36 x 4 Class 8.8 bolt?

2,647 N·m (1,952 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 M36 x 3 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.