M16 bolt torque

An M16 x 2 bolt takes 219 N·m in class 8.8, 313 in 10.9 and 365 in 12.9, dry, at 75% of proof load (161, 231 and 270 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
M16 x 2coarseClass 4.662.584.862.584.846.963.631.342.45,956 lbf26.5 kN
Class 8.816121916121912116480.610915,353 lbf68.3 kN
Class 10.923131323131317323511515621,971 lbf97.7 kN
Class 12.927036527036520227413518325,677 lbf114.2 kN
M16 x 1.5fineClass 4.666.590.266.590.249.967.633.345.16,335 lbf28.2 kN
Class 8.817123217123212917485.711616,331 lbf72.6 kN
Class 10.924533324533318424912316623,371 lbf104.0 kN
Class 12.928738928738921529214319427,313 lbf121.5 kN

Work out M16 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%.

M16 x 2 Class 8.8, dry, plain steel

161ft-lb219N·m

0501001502000100200300ft-lbN·m
Clamp load
15,353 lbf (68.3 kN)
Proof load
91.1 kN

The working

  1. Tensile stress area. A = π/4 × (d − 0.9382 × P)² = π/4 × (16 − 0.9382 × 2)² = 157 mm²
  2. Proof load. Class 8.8 proof stress is 580 MPa, so A × stress = 91,060 N.
  3. Clamp load. 75% of proof load = 68,295 N.
  4. Torque. T = K × D × F = 0.2 × 16 mm × 68.30 kN = 219 N·m (161 ft-lb).

Where the M16 x 2 numbers come from

The M16 x 2 coarse thread has a tensile stress area of 157 mm². A Class 10.9 bolt’s proof stress is 830 MPa, so its proof load is 130,310 N, and 75% of that is a clamp load of 97,733 N.

Torque = K × D × F = 0.20 × 16 mm × 97.73 kN = 313 N·m (231 ft-lb) dry. With oil (K 0.15) it’s 235 N·m (173 ft-lb).

Other sizes

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

Questions

What torque for an M16 x 2 Class 10.9 bolt?

313 N·m (231 ft-lb) dry and 235 N·m (173 ft-lb) oiled, at 75% of proof load. That clamps the joint with 21,971 lbf (97.7 kN).

What torque for an M16 x 2 Class 8.8 bolt?

219 N·m (161 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 M16 x 1.5 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.