M8 Screw Size Chart – Head Dimensions, Drive Sizes & Thread Pitch | Monster Bolts
M8 screw and bolt sizes are common in machinery, automotive, furniture, and fabrication. Use this chart to quickly find head height, head diameter, and drive size for popular M8 types. If you’re new to standards, DIN and ISO numbers are official identifiers that define dimensions (e.g., DIN 912, ISO 7380). Standard coarse thread for M8 is M8-1.25.
Metric M8-1.25 (Coarse) – Dimensions & Drive Sizes
| Type | DIN | ISO | Head Height | Head Diameter | Drive Size |
|---|---|---|---|---|---|
| M8 Hex Bolts (FT) | 933 | 4017 | 5.45 mm | 14.38 mm* | 13 mm WAF |
| M8 Hex Bolts (PT) | 931 | 4014 | 5.45 mm | 14.38 mm* | 13 mm WAF |
| M8 Socket Head Cap | 912 | 4762 | 8.0 mm | 13.27 mm | 6 mm hex |
| M8 Low Head Socket Cap | 7984 | — | 5.0 mm | 13.0 mm | 5 mm hex |
| M8 Button Head Socket | 9427 | 7380 | 4.4 mm | 14.0 mm | 5 mm hex |
| M8 Flat Head Socket | 7991 | 10642 | 4.96 mm | 17.92 mm | 5 mm hex |
| M8 Phillips Flat Head | 965 | — | 4.0 mm | 14.5 mm | #3 Phillips |
| M8 Phillips Pan Head | 7985 | 7045 | 6.15 mm | 16.0 mm | #4 Phillips |
All of these pair with matching M8 nuts and M8 washers.
Legend: PT = Partial Thread, FT = Full Thread. * = Width Across Flats (hex).
- Metric Thread Pitch Table • US TPI (comparison)
- How to Measure Length & Diameter • Printable Ruler (to scale)
- Shop all M8 fasteners — fast shipping from Milton, Florida.
M8 FAQs
What hex key fits an M8 socket head cap screw?
Typically a 6 mm hex key. Low-head and button socket styles commonly use a 5 mm hex.
What nut fits an M8 screw?
M8 screws pair with M8 nuts and M8 washers. Metric fasteners always match by nominal diameter.
What is the standard M8 thread pitch?
Standard coarse pitch is M8-1.25. Fine pitches like M8-1.0 or M8-0.75 exist—verify your tapped hole or nut.
Is an M8 the same as 5/16-18 or 5/16-24?
No. Although diameters are similar, metric and imperial threads are different systems and are not interchangeable.
What tap drill size is used for M8-1.25?
A common tap drill for M8-1.25 is 6.8 mm. Always confirm for your material and application.