Tap Drill Sizes
Tap drill sizes for inch and metric threads, with adjustable thread engagement percentage.
Unified (inch)
| Thread size | Threads per inch | Tap drill ″ | Same drill mm | Nearest drill |
|---|---|---|---|---|
| #4-40 | 40 | 0.089 | 2.26 | #43 |
| #6-32 | 32 | 0.1065 | 2.71 | #36 |
| #8-32 | 32 | 0.136 | 3.45 | #29 |
| #10-24 | 24 | 0.1495 | 3.8 | #25 |
| #12-24 | 24 | 0.177 | 4.5 | #16 |
| 1/4-20 | 20 | 0.201 | 5.11 | #7 |
| 5/16-18 | 18 | 0.257 | 6.53 | F |
| 3/8-16 | 16 | 0.3125 | 7.94 | 5/16 |
| 7/16-14 | 14 | 0.368 | 9.35 | U |
| 1/2-13 | 13 | 0.4219 | 10.7 | 27/64 |
| 9/16-12 | 12 | 0.4844 | 12.3 | 31/64 |
| 5/8-11 | 11 | 0.5312 | 13.5 | 17/32 |
| 3/4-10 | 10 | 0.6562 | 16.7 | 21/32 |
| 7/8-9 | 9 | 0.7656 | 19.4 | 49/64 |
| 1-8 | 8 | 0.875 | 22.2 | 7/8 |
| #4-48 | 48 | 0.0935 | 2.37 | #42 |
| #6-40 | 40 | 0.113 | 2.87 | #33 |
| #8-36 | 36 | 0.136 | 3.45 | #29 |
| #10-32 | 32 | 0.159 | 4.04 | #21 |
| 1/4-28 | 28 | 0.213 | 5.41 | #3 |
| 5/16-24 | 24 | 0.272 | 6.91 | I |
| 3/8-24 | 24 | 0.332 | 8.43 | Q |
| 7/16-20 | 20 | 0.3906 | 9.92 | 25/64 |
| 1/2-20 | 20 | 0.4531 | 11.5 | 29/64 |
| 9/16-18 | 18 | 0.5156 | 13.1 | 33/64 |
| 5/8-18 | 18 | 0.5781 | 14.7 | 37/64 |
| 3/4-16 | 16 | 0.6875 | 17.5 | 11/16 |
| 7/8-14 | 14 | 0.8125 | 20.6 | 13/16 |
| 1-12 | 12 | 0.9219 | 23.4 | 59/64 |
Metric
| Thread size | Pitch | Tap drill mm | Same drill ″ |
|---|---|---|---|
| M3 | 0.5 | 2.5 | 0.0984 |
| M4 | 0.7 | 3.3 | 0.13 |
| M5 | 0.8 | 4.2 | 0.165 |
| M6 | 1 | 5 | 0.197 |
| M8 | 1.25 | 6.8 | 0.268 |
| M10 | 1.5 | 8.5 | 0.335 |
| M12 | 1.75 | 10.2 | 0.402 |
| M14 | 2 | 12 | 0.472 |
| M16 | 2 | 14 | 0.551 |
| M18 | 2.5 | 15.5 | 0.61 |
| M20 | 2.5 | 17.5 | 0.689 |
| M22 | 2.5 | 19.5 | 0.768 |
| M24 | 3 | 21 | 0.827 |
| M27 | 3 | 24 | 0.945 |
| M30 | 3.5 | 26.5 | 1.04 |
| M8x1.0 | 1 | 7 | 0.276 |
| M10x1.0 | 1 | 9 | 0.354 |
| M10x1.25 | 1.25 | 8.8 | 0.346 |
| M12x1.25 | 1.25 | 10.8 | 0.425 |
| M12x1.5 | 1.5 | 10.5 | 0.413 |
| M14x1.5 | 1.5 | 12.5 | 0.492 |
| M16x1.5 | 1.5 | 14.5 | 0.571 |
| M18x1.5 | 1.5 | 16.5 | 0.65 |
| M20x1.5 | 1.5 | 18.5 | 0.728 |
| M24x2.0 | 2 | 22 | 0.866 |
The chart above is 75% thread engagement, the general-purpose default. Open any size to set your own percentage — 60% cuts tapping torque hard and costs little strength in steel.
One page per size
Each size has its own page with the drill in both units, the nearest letter or number drill, and a calculator for any engagement percentage.