ISO metric threads. The pitch is the distance in millimeters from one thread to the next. Coarse is the standard thread when no pitch is given. The coarse tap drill is the diameter minus the pitch.
| Size | Coarse pitch | Coarse tap drill | Fine pitch | Extra fine pitch | Ultra fine pitch |
|---|---|---|---|---|---|
| M1 | 0.25 | 0.75 mm | 0.2 | ||
| M1.2 | 0.25 | 0.95 mm | 0.2 | ||
| M1.4 | 0.3 | 1.1 mm | 0.2 | ||
| M1.6 | 0.35 | 1.25 mm | 0.2 | ||
| M1.7 | 0.35 | 1.35 mm | |||
| M1.8 | 0.35 | 1.45 mm | 0.2 | ||
| M2 | 0.4 | 1.6 mm | 0.25 | ||
| M2.2 | 0.45 | 1.75 mm | 0.25 | ||
| M2.3 | 0.4 | 1.9 mm | |||
| M2.5 | 0.45 | 2.05 mm | 0.35 | ||
| M2.6 | 0.45 | 2.15 mm | |||
| M3 | 0.5 | 2.5 mm | 0.35 | ||
| M3.5 | 0.6 | 2.9 mm | 0.35 | ||
| M4 | 0.7 | 3.3 mm | 0.5 | ||
| M5 | 0.8 | 4.2 mm | 0.5 | ||
| M6 | 1 | 5 mm | 0.75 | ||
| M7 | 1 | 6 mm | 0.75 | ||
| M8 | 1.25 | 6.75 mm | 1 | 0.75 | |
| M9 | 1.25 | 7.75 mm | 1 | 0.75 | |
| M10 | 1.5 | 8.5 mm | 1.25 | 1 | 0.75 |
| M11 | 1.5 | 9.5 mm | 1 | 0.75 | |
| M12 | 1.75 | 10.25 mm | 1.5 | 1.25 | 1 |
| M14 | 2 | 12 mm | 1.5 | 1.25 | 1 |
| M16 | 2 | 14 mm | 1.5 | 1 | |
| M18 | 2.5 | 15.5 mm | 2 | 1.5 | 1 |
| M20 | 2.5 | 17.5 mm | 2 | 1.5 | 1 |
| M22 | 2.5 | 19.5 mm | 2 | 1.5 | 1 |
| M24 | 3 | 21 mm | 2 | 1.5 | 1 |
| M27 | 3 | 24 mm | 2 | 1.5 | 1 |
| M30 | 3.5 | 26.5 mm | 3 | 2 | 1.5 |
| M33 | 3.5 | 29.5 mm | 3 | 2 | 1.5 |
| M36 | 4 | 32 mm | 3 | 2 | 1.5 |
| M39 | 4 | 35 mm | 3 | 2 | 1.5 |
| M42 | 4.5 | 37.5 mm | 4 | 3 | 2 |
| M45 | 4.5 | 40.5 mm | 4 | 3 | 2 |
| M48 | 5 | 43 mm | 4 | 3 | 2 |
| M52 | 5 | 47 mm | 4 | 3 | 2 |
| M56 | 5.5 | 50.5 mm | 4 | 3 | 2 |
| M60 | 5.5 | 54.5 mm | 4 | 3 | 2 |
| M64 | 6 | 58 mm | 4 | 3 | 2 |
| M68 | 6 | 62 mm | 4 | 3 | 2 |
| M72 | 6 | 66 mm | 4 | 3 | 2 |
| M80 | 6 | 74 mm | 4 | 3 | 2 |
| M90 | 6 | 84 mm | 4 | 3 | 2 |
| M100 | 6 | 94 mm | 4 | 3 | 2 |
Reading metric sizes
A size like M12-1.75 x 50 means 12 mm diameter, 1.75 mm pitch, 50 mm long. In Metro part numbers, -F is fine, -X or -Y is extra fine and -Z is ultra fine thread; no suffix is coarse.