| Tap / thread size* | Basic major diameter | Tap drill size** |
|---|---|---|
| M1.6 x 0.35 | 0.063 | 1.25mm or #55 |
| M2 x 0.4 | 0.0787 | 1.60mm or #52 |
| M2.5 x 0.45 | 0.0984 | 2.05mm or #46 |
| M3 x 0.5 | 0.1181 | 2.50mm or #39 |
| M3.5 x 0.6 | 0.1378 | 2.90mm or #32 |
| M4 x 0.7 | 0.1575 | 3.30mm or #30 |
| M5 x 0.8 | 0.1969 | 4.20mm or #19 |
| M6 x 1 | 0.2362 | 5.00mm or #8 |
| M8 x 1.25 | 0.315 | 6.80mm or H |
| M8 x 1 | 0.315 | 7.00mm or J |
| M10 x 1.5 | 0.3937 | 8.50mm or R |
| M10 x 1.25 | 0.3937 | 8.80mm or 11/32 |
| M12 x 1.75 | 0.4724 | 10.20mm or 13/32 |
| M12 x 1.25 | 0.4724 | 10.80mm or 27/64 |
| M14 x 2 | 0.5512 | 12.00mm or 15/32 |
| M14 x 1.5 | 0.5512 | 12.50mm or 1/2 |
| M16 x 2 | 0.6299 | 14.00mm or 35/64 |
| M16 x 1.5 | 0.6299 | 14.50mm or 37/64 |
| M18 x 2.5 | 0.7087 | 15.50mm or 39/64 |
| M18 x 1.5 | 0.7087 | 16.50mm or 21/32 |
| M20 x 2.5 | 0.7874 | 17.50mm or 11/16 |
| M20 x 1.5 | 0.7874 | 18.50mm or 47/64 |
| M22 x 2.5 | 0.8661 | 19.50mm or 49/64 |
| M22 x 1.5 | 0.8661 | 20.50mm or 13/16 |
| M24 x 3 | 0.9449 | 21.00mm or 53/64 |
| M24 x 2 | 0.9449 | 22.00mm or 7/8 |
| M27 x 3 | 1.063 | 24.00mm or 15/16 |
| M27 x 2 | 1.063 | 25.00mm or 1 |