Number drills run from #80 (0.0135 inch) up to #1 (0.228 inch), letter drills continue from A (0.234 inch) to Z (0.413 inch). The most used shop sizes: #43 (0.089), #36 (0.1065), #29 (0.136), #25 (0.1495), #21 (0.159), #7 (0.201), F (0.257), Q (0.332), U (0.368).
Number and letter drills fill the gaps between fractional sizes, which is why tap drill charts are full of them. Click any number from #1 to #60 or any letter for its own page with decimal, metric, the taps it serves and starting RPM.
Tools that go with this chart
Number drills
| Drill | Decimal (in) | mm | Nearest fraction |
|---|---|---|---|
| #1 | 0.2280 | 5.791 | 15/64" (0.2344) |
| #2 | 0.2210 | 5.613 | 7/32" (0.2188) |
| #3 | 0.2130 | 5.410 | 7/32" (0.2188) |
| #4 | 0.2090 | 5.309 | 13/64" (0.2031) |
| #5 | 0.2055 | 5.220 | 13/64" (0.2031) |
| #6 | 0.2040 | 5.182 | 13/64" (0.2031) |
| #7 | 0.2010 | 5.105 | 13/64" (0.2031) |
| #8 | 0.1990 | 5.055 | 13/64" (0.2031) |
| #9 | 0.1960 | 4.978 | 13/64" (0.2031) |
| #10 | 0.1935 | 4.915 | 3/16" (0.1875) |
| #11 | 0.1910 | 4.851 | 3/16" (0.1875) |
| #12 | 0.1890 | 4.801 | 3/16" (0.1875) |
| #13 | 0.1850 | 4.699 | 3/16" (0.1875) |
| #14 | 0.1820 | 4.623 | 3/16" (0.1875) |
| #15 | 0.1800 | 4.572 | 3/16" (0.1875) |
| #16 | 0.1770 | 4.496 | 11/64" (0.1719) |
| #17 | 0.1730 | 4.394 | 11/64" (0.1719) |
| #18 | 0.1695 | 4.305 | 11/64" (0.1719) |
| #19 | 0.1660 | 4.216 | 11/64" (0.1719) |
| #20 | 0.1610 | 4.089 | 5/32" (0.1563) |
| #21 | 0.1590 | 4.039 | 5/32" (0.1563) |
| #22 | 0.1570 | 3.988 | 5/32" (0.1563) |
| #23 | 0.1540 | 3.912 | 5/32" (0.1563) |
| #24 | 0.1520 | 3.861 | 5/32" (0.1563) |
| #25 | 0.1495 | 3.797 | 5/32" (0.1563) |
| #26 | 0.1470 | 3.734 | 9/64" (0.1406) |
| #27 | 0.1440 | 3.658 | 9/64" (0.1406) |
| #28 | 0.1405 | 3.569 | 9/64" (0.1406) |
| #29 | 0.1360 | 3.454 | 9/64" (0.1406) |
| #30 | 0.1285 | 3.264 | 1/8" (0.1250) |
| #31 | 0.1200 | 3.048 | 1/8" (0.1250) |
| #32 | 0.1160 | 2.946 | 7/64" (0.1094) |
| #33 | 0.1130 | 2.870 | 7/64" (0.1094) |
| #34 | 0.1110 | 2.819 | 7/64" (0.1094) |
| #35 | 0.1100 | 2.794 | 7/64" (0.1094) |
| #36 | 0.1065 | 2.705 | 7/64" (0.1094) |
| #37 | 0.1040 | 2.642 | 7/64" (0.1094) |
| #38 | 0.1015 | 2.578 | 3/32" (0.0938) |
| #39 | 0.0995 | 2.527 | 3/32" (0.0938) |
| #40 | 0.0980 | 2.489 | 3/32" (0.0938) |
| #41 | 0.0960 | 2.438 | 3/32" (0.0938) |
| #42 | 0.0935 | 2.375 | 3/32" (0.0938) |
| #43 | 0.0890 | 2.261 | 3/32" (0.0938) |
| #44 | 0.0860 | 2.184 | 3/32" (0.0938) |
| #45 | 0.0820 | 2.083 | 5/64" (0.0781) |
| #46 | 0.0810 | 2.057 | 5/64" (0.0781) |
| #47 | 0.0785 | 1.994 | 5/64" (0.0781) |
| #48 | 0.0760 | 1.930 | 5/64" (0.0781) |
| #49 | 0.0730 | 1.854 | 5/64" (0.0781) |
| #50 | 0.0700 | 1.778 | 1/16" (0.0625) |
| #51 | 0.0670 | 1.702 | 1/16" (0.0625) |
| #52 | 0.0635 | 1.613 | 1/16" (0.0625) |
| #53 | 0.0595 | 1.511 | 1/16" (0.0625) |
| #54 | 0.0550 | 1.397 | 1/16" (0.0625) |
| #55 | 0.0520 | 1.321 | 3/64" (0.0469) |
| #56 | 0.0465 | 1.181 | 3/64" (0.0469) |
| #57 | 0.0430 | 1.092 | 3/64" (0.0469) |
| #58 | 0.0420 | 1.067 | 3/64" (0.0469) |
| #59 | 0.0410 | 1.041 | 3/64" (0.0469) |
| #60 | 0.0400 | 1.016 | 3/64" (0.0469) |
| #61 | 0.0390 | 0.991 | 1/32" (0.0313) |
| #62 | 0.0380 | 0.965 | 1/32" (0.0313) |
| #63 | 0.0370 | 0.940 | 1/32" (0.0313) |
| #64 | 0.0360 | 0.914 | 1/32" (0.0313) |
| #65 | 0.0350 | 0.889 | 1/32" (0.0313) |
| #66 | 0.0330 | 0.838 | 1/32" (0.0313) |
| #67 | 0.0320 | 0.813 | 1/32" (0.0313) |
| #68 | 0.0310 | 0.787 | 1/32" (0.0313) |
| #69 | 0.0292 | 0.742 | 1/32" (0.0313) |
| #70 | 0.0280 | 0.711 | 1/32" (0.0313) |
| #71 | 0.0260 | 0.660 | 1/32" (0.0313) |
| #72 | 0.0250 | 0.635 | 1/32" (0.0313) |
| #73 | 0.0240 | 0.610 | 1/32" (0.0313) |
| #74 | 0.0225 | 0.571 | 1/64" (0.0156) |
| #75 | 0.0210 | 0.533 | 1/64" (0.0156) |
| #76 | 0.0200 | 0.508 | 1/64" (0.0156) |
| #77 | 0.0180 | 0.457 | 1/64" (0.0156) |
| #78 | 0.0160 | 0.406 | 1/64" (0.0156) |
| #79 | 0.0145 | 0.368 | 1/64" (0.0156) |
| #80 | 0.0135 | 0.343 | 1/64" (0.0156) |
Letter drills
| Drill | Decimal (in) | mm | Nearest fraction |
|---|---|---|---|
| A | 0.2340 | 5.944 | 15/64" (0.2344) |
| B | 0.2380 | 6.045 | 15/64" (0.2344) |
| C | 0.2420 | 6.147 | 15/64" (0.2344) |
| D | 0.2460 | 6.248 | 1/4" (0.2500) |
| E | 0.2500 | 6.350 | 1/4" (0.2500) |
| F | 0.2570 | 6.528 | 1/4" (0.2500) |
| G | 0.2610 | 6.629 | 17/64" (0.2656) |
| H | 0.2660 | 6.756 | 17/64" (0.2656) |
| I | 0.2720 | 6.909 | 17/64" (0.2656) |
| J | 0.2770 | 7.036 | 9/32" (0.2813) |
| K | 0.2810 | 7.137 | 9/32" (0.2813) |
| L | 0.2900 | 7.366 | 19/64" (0.2969) |
| M | 0.2950 | 7.493 | 19/64" (0.2969) |
| N | 0.3020 | 7.671 | 19/64" (0.2969) |
| O | 0.3160 | 8.026 | 5/16" (0.3125) |
| P | 0.3230 | 8.204 | 21/64" (0.3281) |
| Q | 0.3320 | 8.433 | 21/64" (0.3281) |
| R | 0.3390 | 8.611 | 11/32" (0.3438) |
| S | 0.3480 | 8.839 | 11/32" (0.3438) |
| T | 0.3580 | 9.093 | 23/64" (0.3594) |
| U | 0.3680 | 9.347 | 3/8" (0.3750) |
| V | 0.3770 | 9.576 | 3/8" (0.3750) |
| W | 0.3860 | 9.804 | 25/64" (0.3906) |
| X | 0.3970 | 10.084 | 25/64" (0.3906) |
| Y | 0.4040 | 10.262 | 13/32" (0.4063) |
| Z | 0.4130 | 10.490 | 13/32" (0.4063) |
Shop the tools for this chart
Frequently asked questions
Which is bigger, a #1 drill or an A drill?
An A drill. Number drills get smaller as the number rises, so #1 at 0.228 inch is the largest number drill, and letter drills start just above it with A at 0.234 inch and run up to Z at 0.413 inch. Together with fractional drills they give a size roughly every few thousandths.
Do I need a full number drill set?
For tapping, most hobbyists get by with the handful of number drills that match their common taps: #43, #36, #29, #25, #21, #7 and F cover 4-40 through 5/16-18. A 60 piece number set is inexpensive, though, and saves a trip every time a new thread size comes up.
Keep going
Figures are from published standards and handbook values, reproduced for convenience. Check critical dimensions against the standard or your tooling manufacturer.