TAP DRILL CHART
Tap Drill Chart
Tap drill sizes for UNC, UNF and UNEF threads from #0 to 1 inch and ISO metric coarse and fine threads from M1.6 to M30, with the decimal drill size and the percent of thread each drill produces.
QUICK LOOKUP
What size drill for 1/4-20 UNC?
- Tap drill
- #7
- Decimal
- 0.2010 in
- mm
- 5.105
- Thread
- 75%
UNC · UNF · UNEF
Inch tap drill chart
| Thread | Series | Tap drill | Decimal in | mm | % thread |
|---|---|---|---|---|---|
| #0-80 | UNF | 3/64" | 0.0469 | 1.191 | 81% |
| #1-64 | UNC | #53 | 0.0595 | 1.511 | 67% |
| #1-72 | UNF | #53 | 0.0595 | 1.511 | 75% |
| #2-56 | UNC | #50 | 0.0700 | 1.778 | 69% |
| #2-64 | UNF | #50 | 0.0700 | 1.778 | 79% |
| #3-48 | UNC | #47 | 0.0785 | 1.994 | 76% |
| #3-56 | UNF | #45 | 0.0820 | 2.083 | 73% |
| #4-40 | UNC | #43 | 0.0890 | 2.261 | 71% |
| #4-48 | UNF | #42 | 0.0935 | 2.375 | 68% |
| #5-40 | UNC | #38 | 0.1015 | 2.578 | 72% |
| #5-44 | UNF | #37 | 0.1040 | 2.642 | 71% |
| #6-32 | UNC | #36 | 0.1065 | 2.705 | 78% |
| #6-40 | UNF | #33 | 0.1130 | 2.870 | 77% |
| #8-32 | UNC | #29 | 0.1360 | 3.454 | 69% |
| #8-36 | UNF | #29 | 0.1360 | 3.454 | 78% |
| #10-24 | UNC | #25 | 0.1495 | 3.797 | 75% |
| #10-32 | UNF | #21 | 0.1590 | 4.039 | 76% |
| #12-24 | UNC | #16 | 0.1770 | 4.496 | 72% |
| #12-28 | UNF | #14 | 0.1820 | 4.623 | 73% |
| #12-32 | UNEF | 3/16" | 0.1875 | 4.762 | 70% |
| 1/4-20 | UNC | #7 | 0.2010 | 5.105 | 75% |
| 1/4-28 | UNF | #3 | 0.2130 | 5.410 | 80% |
| 1/4-32 | UNEF | 7/32" | 0.2188 | 5.556 | 77% |
| 5/16-18 | UNC | F | 0.2570 | 6.528 | 77% |
| 5/16-24 | UNF | I | 0.2720 | 6.909 | 75% |
| 5/16-32 | UNEF | 9/32" | 0.2813 | 7.144 | 77% |
| 3/8-16 | UNC | 5/16" | 0.3125 | 7.938 | 77% |
| 3/8-24 | UNF | Q | 0.3320 | 8.433 | 79% |
| 3/8-32 | UNEF | 11/32" | 0.3438 | 8.731 | 77% |
| 7/16-14 | UNC | U | 0.3680 | 9.347 | 75% |
| 7/16-20 | UNF | 25/64" | 0.3906 | 9.922 | 72% |
| 7/16-28 | UNEF | Y | 0.4040 | 10.262 | 72% |
| 1/2-13 | UNC | 27/64" | 0.4219 | 10.716 | 78% |
| 1/2-20 | UNF | 29/64" | 0.4531 | 11.509 | 72% |
| 1/2-28 | UNEF | 15/32" | 0.4688 | 11.906 | 67% |
| 9/16-12 | UNC | 31/64" | 0.4844 | 12.303 | 72% |
| 9/16-18 | UNF | 1/2" | 0.5000 | 12.700 | 87% |
| 9/16-24 | UNEF | 33/64" | 0.5156 | 13.097 | 87% |
| 5/8-11 | UNC | 17/32" | 0.5313 | 13.494 | 79% |
| 5/8-18 | UNF | 9/16" | 0.5625 | 14.287 | 87% |
| 5/8-24 | UNEF | 37/64" | 0.5781 | 14.684 | 87% |
| 3/4-10 | UNC | 21/32" | 0.6563 | 16.669 | 72% |
| 3/4-16 | UNF | 11/16" | 0.6875 | 17.462 | 77% |
| 3/4-20 | UNEF | 45/64" | 0.7031 | 17.859 | 72% |
| 7/8-9 | UNC | 49/64" | 0.7656 | 19.447 | 76% |
| 7/8-14 | UNF | 51/64" | 0.7969 | 20.241 | 84% |
| 7/8-20 | UNEF | 53/64" | 0.8281 | 21.034 | 72% |
| 1-8 | UNC | 7/8" | 0.8750 | 22.225 | 77% |
| 1-12 | UNF | 59/64" | 0.9219 | 23.416 | 72% |
| 1-20 | UNEF | 61/64" | 0.9531 | 24.209 | 72% |
Drill selections follow the preferred tap drill sizes in Machinery’s Handbook (29th ed., p. 1816) as tabulated in Unified Thread Standard. Percent of thread is calculated: 76.98 × TPI × (major diameter − drill).
ISO METRIC
Metric tap drill chart
| Thread | Pitch | Tap drill mm | Decimal in | Closest inch drill |
|---|---|---|---|---|
| M1.6 × 0.35 | Coarse | 1.25 | 0.0492 | 3/64" (0.0469, 90%) |
| M2 × 0.4 | Coarse | 1.6 | 0.0630 | 1/16" (0.0625, 79%) |
| M2.5 × 0.45 | Coarse | 2.05 | 0.0807 | #46 (0.0810, 76%) |
| M3 × 0.5 | Coarse | 2.5 | 0.0984 | #40 (0.0980, 79%) |
| M3.5 × 0.6 | Coarse | 2.9 | 0.1142 | #33 (0.1130, 81%) |
| M4 × 0.7 | Coarse | 3.3 | 0.1299 | #30 (0.1285, 81%) |
| M5 × 0.8 | Coarse | 4.2 | 0.1654 | #19 (0.1660, 75%) |
| M6 × 1 | Coarse | 5 | 0.1969 | #9 (0.1960, 79%) |
| M8 × 1.25 | Coarse | 6.75 | 0.2657 | 17/64" (0.2656, 77%) |
| M8 × 1 | Fine | 7 | 0.2756 | J (0.2770, 74%) |
| M10 × 1.5 | Coarse | 8.5 | 0.3346 | Q (0.3320, 80%) |
| M10 × 1.25 | Fine | 8.75 | 0.3445 | 11/32" (0.3438, 78%) |
| M10 × 1 | Fine | 9 | 0.3543 | T (0.3580, 70%) |
| M12 × 1.75 | Coarse | 10.25 | 0.4035 | Y (0.4040, 76%) |
| M12 × 1.5 | Fine | 10.5 | 0.4134 | Z (0.4130, 77%) |
| M12 × 1.25 | Fine | 10.75 | 0.4232 | 27/64" (0.4219, 79%) |
| M14 × 2 | Coarse | 12 | 0.4724 | 15/32" (0.4688, 81%) |
| M14 × 1.5 | Fine | 12.5 | 0.4921 | 31/64" (0.4844, 87%) |
| M16 × 2 | Coarse | 14 | 0.5512 | 35/64" (0.5469, 81%) |
| M16 × 1.5 | Fine | 14.5 | 0.5709 | 37/64" (0.5781, 68%) |
| M18 × 2.5 | Coarse | 15.5 | 0.6102 | 39/64" (0.6094, 78%) |
| M18 × 1.5 | Fine | 16.5 | 0.6496 | 21/32" (0.6563, 68%) |
| M20 × 2.5 | Coarse | 17.5 | 0.6890 | 11/16" (0.6875, 78%) |
| M20 × 1.5 | Fine | 18.5 | 0.7283 | 47/64" (0.7344, 69%) |
| M22 × 2.5 | Coarse | 19.5 | 0.7677 | 49/64" (0.7656, 79%) |
| M22 × 1.5 | Fine | 20.5 | 0.8071 | 13/16" (0.8125, 70%) |
| M24 × 3 | Coarse | 21 | 0.8268 | 53/64" (0.8281, 76%) |
| M24 × 2 | Fine | 22 | 0.8661 | 55/64" (0.8594, 84%) |
| M27 × 3 | Coarse | 24 | 0.9449 | 15/16" (0.9375, 82%) |
| M30 × 3.5 | Coarse | 26.5 | 1.0433 | 1" (1.0000, 101%) |
Pitches per ISO 261/262. The tap drill is the major diameter minus the pitch, which gives about 77% thread. Common practice rounds some values to stocked drills — 6.8 mm for M8 and 10.2 mm for M12. The inch drill column shows the closest number, letter or fractional drill and the thread percentage it would give.
CHOOSING A DRILL
Percent of thread is a trade-off.
A full 100% thread is only about 5% stronger than a 75% thread but takes much more torque to tap and breaks more taps. Most charts aim for 65–80%. Go toward the lower end in stainless and other tough materials, and higher in soft or thin material where every bit of engagement counts.
These sizes are for cutting taps. Form (roll) taps displace metal instead of cutting it and need a larger drill; use the tap maker’s chart for those.
Need the decimal size of a drill? Open the drill size chart.