ISO metric thread drill sizes for coarse and fine thread forms. Tap drill sizes shown are for approximately 75% thread engagement. Based on ISO 68-1 standard.
Coarse Thread Sizes
| Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) |
|---|---|---|---|---|---|---|---|
| M1 × 0.25 | 0.75 | M3.5 × 0.6 | 2.90 | M12 × 1.75 | 10.20 | M36 × 4 | 32.00 |
| M1.1 × 0.25 | 0.85 | M4 × 0.7 | 3.30 | M14 × 2 | 12.00 | M39 × 4 | 35.00 |
| M1.2 × 0.25 | 0.95 | M4.5 × 0.75 | 3.70 | M16 × 2 | 14.00 | M42 × 4.5 | 37.50 |
| M1.4 × 0.3 | 1.10 | M5 × 0.8 | 4.20 | M18 × 2.5 | 15.50 | M45 × 4.5 | 40.50 |
| M1.6 × 0.35 | 1.25 | M6 × 1 | 5.00 | M20 × 2.5 | 17.50 | M48 × 5 | 43.00 |
| M1.8 × 0.35 | 1.45 | M7 × 1 | 6.00 | M22 × 2.5 | 19.50 | M52 × 5 | 47.00 |
| M2 × 0.4 | 1.60 | M8 × 1.25 | 6.80 | M24 × 3 | 21.00 | M56 × 5.5 | 50.50 |
| M2.2 × 0.45 | 1.75 | M9 × 1.25 | 7.80 | M27 × 3 | 24.00 | M60 × 5.5 | 54.50 |
| M2.5 × 0.45 | 2.05 | M10 × 1.5 | 8.50 | M30 × 3.5 | 26.50 | M64 × 6 | 58.00 |
| M3 × 0.5 | 2.50 | M11 × 1.5 | 9.50 | M33 × 3.5 | 29.50 | M68 × 6 | 62.00 |
Fine Thread Sizes
| Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) | Thread Size | Tap Drill (mm) |
|---|---|---|---|---|---|---|---|
| M4 × 0.35 | 3.60 | M10 × 0.75 | 9.25 | M16 × 1 | 15.0 | M24 × 1.5 | 22.5 |
| M4 × 0.5 | 3.50 | M10 × 1 | 9.0 | M16 × 1.5 | 15.0 | M24 × 2 | 22.0 |
| M5 × 0.5 | 4.50 | M10 × 1.25 | 8.8 | M18 × 1 | 17.0 | M26 × 1.5 | 24.5 |
| M6 × 0.5 | 5.50 | M11 × 1 | 10.0 | M18 × 2 | 16.0 | M27 × 1.5 | 25.5 |
| M6 × 0.75 | 5.25 | M12 × 0.75 | 11.25 | M20 × 1 | 19.0 | M27 × 2 | 25.0 |
| M7 × 0.75 | 6.25 | M12 × 1 | 11.0 | M20 × 1.5 | 18.5 | M28 × 1.5 | 26.5 |
| M8 × 0.5 | 7.00 | M12 × 1.5 | 10.5 | M20 × 2 | 18.0 | M30 × 1.5 | 28.5 |
| M8 × 0.75 | 7.25 | M14 × 1 | 13.0 | M22 × 1 | 21.0 | M30 × 2 | 28.0 |
| M8 × 1 | 7.50 | M14 × 1.25 | 12.8 | M22 × 1.5 | 20.5 | M33 × 2 | 31.0 |
| M9 × 1 | 8.00 | M14 × 1.5 | 12.5 | M22 × 2 | 20.0 | M36 × 3 | 36.0 |
Basic ISO Thread Profile
The design principles of ISO general-purpose metric screw threads ("M" series threads) are defined in international standard ISO 68-1. Each thread is characterised by its major diameter D and its pitch P.
ISO metric threads consist of a symmetric V-shaped thread. In the plane of the thread axis, the flanks of the V have an angle of 60° to each other.
The outermost 1/8 and the innermost 1/4 of the height H of the V-shape are cut off from the profile.
Tap drill size formula: Drill = Major Diameter − Pitch
e.g. M10 × 1.5 → 10 − 1.5 = 8.5mm drill
ISO 68-1 metric thread profile
→ Also see Preferred Metric Thread Sizes → Imperial Thread Data