Metric Bolts — Complete Size Reference

Complete reference for metric coarse bolts from M2 to M30. Wrench sizes, thread pitch, tap drills, torque specifications, and applications.

M24 mm wrench · 0.4 mm pitch · 0.5 Nm M2.55 mm wrench · 0.45 mm pitch · 0.9 Nm M35.5 mm wrench · 0.5 mm pitch · 1.6 Nm M47 mm wrench · 0.7 mm pitch · 3.5 Nm M58 mm wrench · 0.8 mm pitch · 7 Nm M610 mm wrench · 1.0 mm pitch · 12 Nm M813 mm wrench · 1.25 mm pitch · 25 Nm M1017 mm wrench · 1.5 mm pitch · 50 Nm M1219 mm wrench · 1.75 mm pitch · 85 Nm M1422 mm wrench · 2.0 mm pitch · 130 Nm M1624 mm wrench · 2.0 mm pitch · 180 Nm M1827 mm wrench · 2.5 mm pitch · 260 Nm M2030 mm wrench · 2.5 mm pitch · 350 Nm M2232 mm wrench · 2.5 mm pitch · 450 Nm M2436 mm wrench · 3.0 mm pitch · 550 Nm M2741 mm wrench · 3.0 mm pitch · 750 Nm M3046 mm wrench · 3.5 mm pitch · 950 Nm

About metric bolts

Metric bolts are designated by their nominal diameter in millimeters (e.g., M8 = 8mm diameter). The most common thread type is metric coarse, defined in ISO 261.

Metric bolt designation

A metric bolt is designated as: M[diameter]×[pitch]

M8 = 8mm nominal diameter
M8×1.25 = 8mm diameter with 1.25mm thread pitch (coarse)
M8×1.0 = 8mm diameter with 1.0mm thread pitch (fine)

Common metric bolt sizes

The most commonly used metric bolt sizes are M3, M4, M5, M6, M8, M10, and M12. These sizes cover the majority of general machinery, automotive, and structural applications.

Metric bolt property classes

Metric bolts are graded by property class:

4.6, 4.8: Low carbon steel, low strength
5.6, 5.8: Low/medium carbon steel, medium strength
8.8: Medium carbon steel, quenched and tempered (most common)
10.9: Alloy steel, quenched and tempered (high strength)
12.9: Alloy steel, quenched and tempered (very high strength)