Tap Drill Chart
Standard tap drill sizes for about 75% thread, which is right for most cut taps in steel and aluminum. Form (roll) taps need a larger drill - check the tap maker's chart.
Inch - UNC / UNF
| Tap | Drill | Decimal (in) |
|---|---|---|
| #4-40 UNC | #43 | .0890 |
| #6-32 UNC | #36 | .1065 |
| #8-32 UNC | #29 | .1360 |
| #10-24 UNC | #25 | .1495 |
| #10-32 UNF | #21 | .1590 |
| 1/4-20 UNC | #7 | .2010 |
| 1/4-28 UNF | #3 | .2130 |
| 5/16-18 UNC | F | .2570 |
| 5/16-24 UNF | I | .2720 |
| 3/8-16 UNC | 5/16 | .3125 |
| 3/8-24 UNF | Q | .3320 |
| 7/16-14 UNC | U | .3680 |
| 7/16-20 UNF | 25/64 | .3906 |
| 1/2-13 UNC | 27/64 | .4219 |
| 1/2-20 UNF | 29/64 | .4531 |
| 9/16-12 UNC | 31/64 | .4844 |
| 9/16-18 UNF | 33/64 | .5156 |
| 5/8-11 UNC | 17/32 | .5312 |
| 5/8-18 UNF | 37/64 | .5781 |
| 3/4-10 UNC | 21/32 | .6562 |
| 3/4-16 UNF | 11/16 | .6875 |
| 7/8-9 UNC | 49/64 | .7656 |
| 7/8-14 UNF | 13/16 | .8125 |
| 1-8 UNC | 7/8 | .8750 |
| 1-12 UNF | 59/64 | .9219 |
Metric coarse
| Tap | Drill (mm) | Decimal (in) |
|---|---|---|
| M3 x 0.5 | 2.5 | .0984 |
| M4 x 0.7 | 3.3 | .1299 |
| M5 x 0.8 | 4.2 | .1654 |
| M6 x 1.0 | 5.0 | .1969 |
| M8 x 1.25 | 6.8 | .2677 |
| M10 x 1.5 | 8.5 | .3346 |
| M12 x 1.75 | 10.2 | .4016 |
| M14 x 2.0 | 12.0 | .4724 |
| M16 x 2.0 | 14.0 | .5512 |
| M20 x 2.5 | 17.5 | .6890 |
Metric rule of thumb: tap drill = major diameter - pitch.
M8 x 1.25 → 6.75, use a 6.8 mm drill.
Common questions
What drill for a 1/4-20 tap? #7 (.201").
5/16-18? F (.257").
3/8-16? 5/16 (.3125").
M6 x 1.0? 5.0 mm.
Printable PDF version - Tap Drill Chart
Clean letter-size sheet for the toolbox or shop wall. Instant download, $3.49.
Clean letter-size sheet for the toolbox or shop wall. Instant download, $3.49.