Bolt Dimensions & Thread Sizes (Metric)
Comprehensive table of standard metric bolt sizes with diameters, thread pitch, tapping, and clearance information
Metric Bolt Size Chart
| Thread Size | Major Diameter (mm) | Minor Diameter (mm) | Thread Pitch (mm) | Pitch Diameter (mm) | Tapping Drill Diameter (mm) | Clearance Hole Diameter (mm) |
|---|---|---|---|---|---|---|
| M1 | 1.0 | 0.729 | 0.25 | 0.838 | 0.75 | 1.3 |
| M1.1 | 1.1 | 0.829 | 0.25 | 0.938 | 0.85 | 1.4 |
| M1.2 | 1.2 | 0.929 | 0.25 | 1.038 | 0.95 | 1.5 |
| M1.4 | 1.4 | 1.075 | 0.30 | 1.205 | 1.10 | 1.8 |
| M1.6 | 1.6 | 1.221 | 0.35 | 1.373 | 1.25 | 2.0 |
| M1.8 | 1.8 | 1.421 | 0.35 | 1.573 | 1.45 | 2.3 |
| M2 | 2.0 | 1.567 | 0.40 | 1.740 | 1.60 | 2.6 |
| M2.2 | 2.2 | 1.713 | 0.45 | 1.908 | 1.75 | 2.9 |
| M2.5 | 2.5 | 2.013 | 0.45 | 2.208 | 2.05 | 3.1 |
| M3 | 3.0 | 2.459 | 0.50 | 2.675 | 2.50 | 3.6 |
| M3.5 | 3.5 | 2.850 | 0.60 | 3.110 | 2.90 | 4.2 |
| M4 | 4.0 | 3.242 | 0.70 | 3.545 | 3.30 | 4.8 |
| M4.5 | 4.5 | 3.688 | 0.75 | 4.013 | 3.80 | 5.3 |
| M5 | 5.0 | 4.134 | 0.80 | 4.480 | 4.20 | 5.8 |
| M6 | 6.0 | 4.917 | 1.00 | 5.350 | 5.00 | 7.0 |
| M7 | 7.0 | 5.917 | 1.00 | 6.350 | 6.00 | 8.0 |
| M8 | 8.0 | 6.647 | 1.25 | 7.188 | 6.80 | 10.0 |
| M9 | 9.0 | 7.647 | 1.25 | 8.188 | 7.80 | 11.0 |
| M10 | 10.0 | 8.376 | 1.50 | 9.026 | 8.50 | 12.0 |
| M11 | 11.0 | 9.376 | 1.50 | 10.026 | 9.50 | 13.5 |
| M12 | 12.0 | 10.106 | 1.75 | 10.863 | 10.20 | 15.0 |
| M14 | 14.0 | 11.835 | 2.00 | 12.701 | 12.00 | 17.0 |
| M16 | 16.0 | 13.835 | 2.00 | 14.701 | 14.00 | 19.0 |
| M18 | 18.0 | 15.394 | 2.50 | 16.376 | 15.50 | 22.0 |
| M20 | 20.0 | 17.294 | 2.50 | 18.376 | 17.50 | 24.0 |
| M22 | 22.0 | 19.294 | 2.50 | 20.376 | 19.50 | 26.0 |
| M24 | 24.0 | 20.752 | 3.00 | 22.051 | 21.00 | 28.0 |
| M27 | 27.0 | 23.752 | 3.00 | 25.051 | 24.00 | 33.0 |
| M30 | 30.0 | 26.211 | 3.50 | 27.727 | 26.50 | 35.0 |
| M33 | 33.0 | 29.211 | 3.50 | 30.727 | 29.50 | 38.0 |
| M36 | 36.0 | 31.670 | 4.00 | 33.402 | 32.00 | 41.0 |
| M39 | 39.0 | 34.670 | 4.00 | 36.402 | 35.00 | 44.0 |
| M42 | 42.0 | 37.129 | 4.50 | 39.077 | 37.50 | 47.0 |
| M45 | 45.0 | 40.129 | 4.50 | 42.077 | 40.50 | 50.0 |
| M48 | 48.0 | 42.857 | 5.00 | 44.752 | 43.00 | 53.0 |
| M52 | 52.0 | 46.587 | 5.00 | 48.752 | 47.00 | 57.0 |
| M56 | 56.0 | 50.046 | 5.50 | 52.428 | 50.50 | 61.0 |
| M60 | 60.0 | 54.046 | 5.50 | 56.428 | 54.50 | 65.0 |
| M64 | 64.0 | 57.505 | 6.00 | 60.103 | 58.00 | 69.0 |
| M68 | 68.0 | 61.505 | 6.00 | 64.103 | 62.00 | 73.0 |
About Metric Bolt Dimensions & Thread Sizes
This detailed metric bolt dimensions and thread size reference provides standardized data for ISO and DIN metric bolts used across engineering, manufacturing, and mechanical design applications. The chart includes thread size, major and minor diameters, thread pitch, pitch diameter, tapping drill diameter, and clearance hole diameter—all essential parameters for accurate fastener selection and design validation.
Understanding these bolt dimension properties helps engineers ensure proper thread engagement, precise hole sizing, and optimal joint performance. By following ISO metric thread standards (ISO 68, ISO 261, ISO 965), this table supports accurate design, assembly, and maintenance of components requiring reliable threaded connections.
Metric Bolt Property Definitions
- Thread Size – Standard metric designation (e.g., M6, M12) defining the nominal diameter and pitch of the bolt thread.
- Major Diameter (mm) – The maximum external thread diameter; used for selecting compatible nuts and tapped holes.
- Minor Diameter (mm) – The root diameter at the base of threads; critical for determining tensile and shear strength.
- Thread Pitch (mm) – The distance between adjacent threads; ensures correct matching between male and female threads.
- Pitch Diameter (mm) – The diameter where thread width equals groove width; defines accurate thread fit and engagement.
- Tapping Drill Diameter (mm) – Recommended drill size for producing internal threads to correctly fit the specified bolt.
- Clearance Hole Diameter (mm) – Free-fit hole size allowing a bolt to pass through without thread contact, ensuring easy alignment during assembly.
Applications and Engineering Use
The metric bolt size chart is widely used in mechanical engineering, product design, manufacturing, automotive, and aerospace industries. It assists in selecting proper fasteners for components subjected to tension, shear, and dynamic loading, ensuring durability and reliability under service conditions.
Referencing this dataset allows engineers and designers to ensure compliance with ISO metric thread standards, maintain consistent assembly accuracy, and minimize dimensional errors in machinery, equipment, and structural designs. By applying the correct thread dimensions, you can achieve secure, efficient, and standardized fastening across global projects.
This page serves as a quick engineering reference for metric fasteners, offering easy access to bolt size, thread pitch, and clearance hole data used in precision design and high-quality manufacturing.