What size wrench or spanner fits M16?

M16 bolt uses a 24 mm wrench or spanner, measured across the flats of the hex head.

What is the torque for M16?

A typical tightening torque for M16 bolt in 8.8 on dry threads is about 180 Nm (132.8 ft·lb). Always confirm against the manufacturer spec for important joints.

What thread pitch and tap drill does M16 use?

M16 bolt has a thread pitch of 2.0 mm and uses a 14 mm tap drill, with a 17.5 mm clearance hole.

What is M16 used for?

M16 is commonly used in structural steel, heavy machinery, automotive. It is one of the most popular sizes in its category.

What is the closest imperial size to M16?

The closest imperial size to M16 is approximately ~5/8 inch, though they are not exactly interchangeable.

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M16 bolt size

24 mm wrench

across-flats spanner / socket size for M16

M16 bolt — Structural steel, heavy machinery, automotive.

Full specification

System	Metric coarse
Nominal diameter	16 mm
Thread pitch	2.0 mm
Wrench / spanner (across flats)	24 mm
Tap drill	14 mm
Clearance hole	17.5 mm
Common grade / class	8.8
Typical torque	180 Nm (132.8 ft·lb)
Closest other-system size	~5/8 inch

🔧 Torque unit converter

Newton-metres (Nm) Foot-pounds (ft·lb) Inch-pounds (in·lb)

Pre-filled with the typical torque for M16 (8.8, dry). Edit any field to convert.

⚠️ Torque values here are general references for 8.8 on clean, dry threads. Lubrication, coatings, and the joint material change the figure significantly. For structural, automotive, or safety-critical work, always use the torque specified by the manufacturer or engineer.

About M16

Structural steel, heavy machinery, automotive.

A 14 mm tap drill is correct for M16 coarse thread. The standard clearance hole is 17.5 mm.

M16 is part of the ISO metric coarse thread series, defined in ISO 261. The wrench size 24 mm is measured across the flats of the hex head.

Common applications

M16 bolts are widely used in:

Structural steel, heavy machinery, automotive
General machinery and equipment assembly
Automotive components and repairs
Structural connections (when specified by engineer)
Furniture and fixture assembly

Material and grade information

The typical grade for M16 is 8.8. This indicates:

Property class 8.8: Medium carbon steel, quenched and tempered
Tensile strength: 800 MPa minimum
Yield strength: 640 MPa minimum (0.2% proof stress)
Common coatings: Zinc plated, hot-dip galvanized, or plain

Frequently asked questions

What size wrench or spanner fits M16?: M16 bolt uses a 24 mm wrench or spanner, measured across the flats of the hex head.
What is the torque for M16?: A typical tightening torque for M16 bolt in 8.8 on dry threads is about 180 Nm (132.8 ft·lb). Always confirm against the manufacturer spec for important joints.
What thread pitch and tap drill does M16 use?: M16 bolt has a thread pitch of 2.0 mm and uses a 14 mm tap drill, with a 17.5 mm clearance hole.
What is M16 used for?: M16 is commonly used in structural steel, heavy machinery, automotive. It is one of the most popular sizes in its category.
What is the closest imperial size to M16?: The closest imperial size to M16 is approximately ~5/8 inch, though they are not exactly interchangeable.