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Every dimension, torque value, and thread specification for the M16 metric bolt in one reference card. M16 Bolt Specifications M16 is one of the most common metric fastener sizes in UK engineering, used across heavy structural and high-load joints.
| Property |
Value |
Standard |
| Nominal diameter |
16.0 mm |
ISO 261 |
| Coarse pitch |
2.0 mm |
ISO 261 |
| Fine pitch |
1.5 mm |
ISO 261 |
| Tap drill (coarse, 75% engagement) |
14.0 mm |
ISO 2306 |
| Tap drill (fine) |
14.5 mm |
ISO 2306 |
| Clearance hole - close |
17.0 mm |
ISO 273 |
| Clearance hole - medium |
17.5 mm |
ISO 273 |
| Clearance hole - coarse |
18.5 mm |
ISO 273 |
| Hex head A/F (spanner size) |
24.0 mm |
ISO 4014 |
| Hex head height |
10.0 mm |
ISO 4014 |
| Socket head cap screw head dia |
24.0 mm |
ISO 4762 |
| Socket head hex key size |
14.0 mm |
ISO 4762 |
| Tensile stress area |
157 mm^2 |
ISO 898-1 |
| Minimum tensile strength 8.8 |
800 MPa |
ISO 898-1 |
| Minimum tensile strength 10.9 |
1040 MPa |
ISO 898-1 |
| Proof load 8.8 |
91.1 kN |
ISO 898-1 |
| Proof load 10.9 |
130.3 kN |
ISO 898-1 |
| Torque dry, class 8.8 |
210 Nm |
VDI 2230 |
| Torque dry, class 10.9 |
295 Nm |
VDI 2230 |
| Torque dry, class 12.9 |
345 Nm |
VDI 2230 |
M16 thread pitch
Standard M16 bolts use a 2.0 mm coarse pitch. Fine pitch M16 x 1.5 is used where vibration resistance matters or in thin-wall components. Coarse pitch is the default - if a drawing says M16 with no pitch specified, it means M16 x 2.0 coarse.
M16 tap drill size
For M16 x 2.0 coarse pitch with 75% thread engagement, drill 14.0 mm. For fine pitch, drill 14.5 mm. Smaller drills give more engagement but increase tap breakage risk without meaningful strength gain.
M16 clearance hole
For a clearance hole where the bolt passes through, use 17.0 mm (close fit), 17.5 mm (medium), or 18.5 mm (coarse) per ISO 273.
M16 torque values
Dry M16 property class 8.8: torque to 210 Nm. Class 10.9: 295 Nm. Class 12.9: 345 Nm. These values target 90% proof load with K=0.20 dry thread friction. If threads are oiled or coated, reduce by 20-25%. For critical joints, always verify against the fastener manufacturer's datasheet.
M16 spanner and hex key
An M16 hex head bolt (ISO 4014) has 24.0 mm across flats, so you need a 24.0 mm spanner or socket. M16 socket head cap screws (ISO 4762) have 24.0 mm head diameter and need a 14.0 mm hex key (Allen key).
Related standards
- ISO 261 - ISO general-purpose metric screw threads
- ISO 273 - Fasteners: clearance holes for bolts and screws
- ISO 898-1 - Mechanical properties of carbon steel fasteners
- ISO 4014 - Hexagon head bolts, product grades A and B
- ISO 4762 - Hexagon socket head cap screws
- VDI 2230 - Systematic calculation of bolted joints
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Frequently Asked Questions
What is the thread pitch of an M16 bolt?
A standard M16 bolt has a coarse thread pitch of 2.0 mm per ISO 261. The fine pitch version is M16 x 1.5. If a drawing says M16 with no pitch specified, it means M16 x 2.0 coarse.
What is the tap drill size for M16?
For M16 x 2.0 coarse pitch with 75% thread engagement, drill 14.0 mm. For fine pitch, drill 14.5 mm. These values give a good balance of thread strength and tapping ease.
What torque is an M16 bolt rated for?
For a dry M16 property class 8.8 bolt, the standard torque is 210 Nm. Class 10.9 takes 295 Nm, class 12.9 takes 345 Nm. Values are per VDI 2230 at 90% proof load with nut factor K=0.20. Reduce by 20-25% if threads are lubricated.
What spanner size fits an M16 bolt?
An M16 hex head bolt (ISO 4014) has a 24.0 mm across-flats (A/F) dimension, so you need a 24.0 mm spanner or socket. An M16 socket head cap screw uses a 14.0 mm hex key (Allen key).
What is the M16 standard pitch?
The M16 standard pitch is 2.0 mm, the ISO 261 coarse pitch used by default. If a drawing specifies M16 with no pitch, it means M16 x 2.0 coarse. The fine pitch option for the M16 thread is 1.5 mm, used where vibration resistance matters or in thin-wall components.
What is the M16 pitch?
The M16 pitch is 2.0 mm for the standard coarse thread per ISO 261, meaning the threads sit 2.0 mm apart. A fine pitch M16 x 1.5 is also available. To tap an M16 x 2.0 thread at 75 percent engagement, drill 14.0 mm per ISO 2306; for the fine pitch use 14.5 mm.
What is the M16 clearance hole?
An M16 clearance hole, where the bolt passes straight through, is 17.0 mm for a close fit, 17.5 mm for medium, or 18.5 mm for coarse, all per ISO 273. Use the close 17.0 mm hole where alignment matters and the larger sizes where assembly tolerance is needed. This differs from the 14.0 mm tap drill used for a threaded M16 hole.
What is the M16 hole size?
The M16 hole size depends on the job. For a clearance hole the bolt passes through, use 17.0 mm close, 17.5 mm medium or 18.5 mm coarse per ISO 273. For a tapped thread, drill 14.0 mm at 75 percent engagement per ISO 2306. The M16 itself is a 16.0 mm nominal diameter bolt per ISO 261.
What are the M16 bolt dimensions?
The M16 bolt has a 16.0 mm nominal diameter and a 2.0 mm coarse pitch per ISO 261. The hex head is 24.0 mm across flats with a 10.0 mm head height per ISO 4014. The tensile stress area of an M16 thread is 157 mm squared per ISO 898-1, and the clearance hole ranges from 17.0 mm close to 18.5 mm coarse per ISO 273.