Three complete series in one place: number drills from #1 to #80, letter drills from A to Z, and fractional drills from 1/64 inch to 1 inch, each with the decimal inch and millimetre value.
Eighty sizes. Remember that the numbering runs the opposite way to the diameter.
| Number drill | Decimal inch | Millimetres |
|---|---|---|
| #1 | 0.2280 | 5.791 |
| #2 | 0.2210 | 5.613 |
| #3 | 0.2130 | 5.410 |
| #4 | 0.2090 | 5.309 |
| #5 | 0.2055 | 5.220 |
| #6 | 0.2040 | 5.182 |
| #7 | 0.2010 | 5.105 |
| #8 | 0.1990 | 5.055 |
| #9 | 0.1960 | 4.978 |
| #10 | 0.1935 | 4.915 |
| #11 | 0.1910 | 4.851 |
| #12 | 0.1890 | 4.801 |
| #13 | 0.1850 | 4.699 |
| #14 | 0.1820 | 4.623 |
| #15 | 0.1800 | 4.572 |
| #16 | 0.1770 | 4.496 |
| #17 | 0.1730 | 4.394 |
| #18 | 0.1695 | 4.305 |
| #19 | 0.1660 | 4.216 |
| #20 | 0.1610 | 4.089 |
| #21 | 0.1590 | 4.039 |
| #22 | 0.1570 | 3.988 |
| #23 | 0.1540 | 3.912 |
| #24 | 0.1520 | 3.861 |
| #25 | 0.1495 | 3.797 |
| #26 | 0.1470 | 3.734 |
| #27 | 0.1440 | 3.658 |
| #28 | 0.1405 | 3.569 |
| #29 | 0.1360 | 3.454 |
| #30 | 0.1285 | 3.264 |
| #31 | 0.1200 | 3.048 |
| #32 | 0.1160 | 2.946 |
| #33 | 0.1130 | 2.870 |
| #34 | 0.1110 | 2.819 |
| #35 | 0.1100 | 2.794 |
| #36 | 0.1065 | 2.705 |
| #37 | 0.1040 | 2.642 |
| #38 | 0.1015 | 2.578 |
| #39 | 0.0995 | 2.527 |
| #40 | 0.0980 | 2.489 |
| #41 | 0.0960 | 2.438 |
| #42 | 0.0935 | 2.375 |
| #43 | 0.0890 | 2.261 |
| #44 | 0.0860 | 2.184 |
| #45 | 0.0820 | 2.083 |
| #46 | 0.0810 | 2.057 |
| #47 | 0.0785 | 1.994 |
| #48 | 0.0760 | 1.930 |
| #49 | 0.0730 | 1.854 |
| #50 | 0.0700 | 1.778 |
| #51 | 0.0670 | 1.702 |
| #52 | 0.0635 | 1.613 |
| #53 | 0.0595 | 1.511 |
| #54 | 0.0550 | 1.397 |
| #55 | 0.0520 | 1.321 |
| #56 | 0.0465 | 1.181 |
| #57 | 0.0430 | 1.092 |
| #58 | 0.0420 | 1.067 |
| #59 | 0.0410 | 1.041 |
| #60 | 0.0400 | 1.016 |
| #61 | 0.0390 | 0.991 |
| #62 | 0.0380 | 0.965 |
| #63 | 0.0370 | 0.940 |
| #64 | 0.0360 | 0.914 |
| #65 | 0.0350 | 0.889 |
| #66 | 0.0330 | 0.838 |
| #67 | 0.0320 | 0.813 |
| #68 | 0.0310 | 0.787 |
| #69 | 0.0292 | 0.742 |
| #70 | 0.0280 | 0.711 |
| #71 | 0.0260 | 0.660 |
| #72 | 0.0250 | 0.635 |
| #73 | 0.0240 | 0.610 |
| #74 | 0.0225 | 0.572 |
| #75 | 0.0210 | 0.533 |
| #76 | 0.0200 | 0.508 |
| #77 | 0.0180 | 0.457 |
| #78 | 0.0160 | 0.406 |
| #79 | 0.0145 | 0.368 |
| #80 | 0.0135 | 0.343 |
Twenty-six sizes covering the gaps between the number and fractional series.
| Letter drill | Decimal inch | Millimetres |
|---|---|---|
| A | 0.2340 | 5.944 |
| B | 0.2380 | 6.045 |
| C | 0.2420 | 6.147 |
| D | 0.2460 | 6.248 |
| E | 0.2500 | 6.350 |
| F | 0.2570 | 6.528 |
| G | 0.2610 | 6.629 |
| H | 0.2660 | 6.756 |
| I | 0.2720 | 6.909 |
| J | 0.2770 | 7.036 |
| K | 0.2810 | 7.137 |
| L | 0.2900 | 7.366 |
| M | 0.2950 | 7.493 |
| N | 0.3020 | 7.671 |
| O | 0.3160 | 8.026 |
| P | 0.3230 | 8.204 |
| Q | 0.3320 | 8.433 |
| R | 0.3390 | 8.611 |
| S | 0.3480 | 8.839 |
| T | 0.3580 | 9.093 |
| U | 0.3680 | 9.347 |
| V | 0.3770 | 9.576 |
| W | 0.3860 | 9.804 |
| X | 0.3970 | 10.084 |
| Y | 0.4040 | 10.262 |
| Z | 0.4130 | 10.490 |
Sixty-four sizes in steps of 1/64 inch. Fractions are shown reduced.
| Fractional drill | Decimal inch | Millimetres |
|---|---|---|
| 1/64 in | 0.0156 | 0.397 |
| 1/32 in | 0.0312 | 0.794 |
| 3/64 in | 0.0469 | 1.191 |
| 1/16 in | 0.0625 | 1.587 |
| 5/64 in | 0.0781 | 1.984 |
| 3/32 in | 0.0938 | 2.381 |
| 7/64 in | 0.1094 | 2.778 |
| 1/8 in | 0.1250 | 3.175 |
| 9/64 in | 0.1406 | 3.572 |
| 5/32 in | 0.1562 | 3.969 |
| 11/64 in | 0.1719 | 4.366 |
| 3/16 in | 0.1875 | 4.763 |
| 13/64 in | 0.2031 | 5.159 |
| 7/32 in | 0.2188 | 5.556 |
| 15/64 in | 0.2344 | 5.953 |
| 1/4 in | 0.2500 | 6.350 |
| 17/64 in | 0.2656 | 6.747 |
| 9/32 in | 0.2812 | 7.144 |
| 19/64 in | 0.2969 | 7.541 |
| 5/16 in | 0.3125 | 7.938 |
| 21/64 in | 0.3281 | 8.334 |
| 11/32 in | 0.3438 | 8.731 |
| 23/64 in | 0.3594 | 9.128 |
| 3/8 in | 0.3750 | 9.525 |
| 25/64 in | 0.3906 | 9.922 |
| 13/32 in | 0.4062 | 10.319 |
| 27/64 in | 0.4219 | 10.716 |
| 7/16 in | 0.4375 | 11.113 |
| 29/64 in | 0.4531 | 11.509 |
| 15/32 in | 0.4688 | 11.906 |
| 31/64 in | 0.4844 | 12.303 |
| 1/2 in | 0.5000 | 12.700 |
| 33/64 in | 0.5156 | 13.097 |
| 17/32 in | 0.5312 | 13.494 |
| 35/64 in | 0.5469 | 13.891 |
| 9/16 in | 0.5625 | 14.287 |
| 37/64 in | 0.5781 | 14.684 |
| 19/32 in | 0.5938 | 15.081 |
| 39/64 in | 0.6094 | 15.478 |
| 5/8 in | 0.6250 | 15.875 |
| 41/64 in | 0.6406 | 16.272 |
| 21/32 in | 0.6562 | 16.669 |
| 43/64 in | 0.6719 | 17.066 |
| 11/16 in | 0.6875 | 17.462 |
| 45/64 in | 0.7031 | 17.859 |
| 23/32 in | 0.7188 | 18.256 |
| 47/64 in | 0.7344 | 18.653 |
| 3/4 in | 0.7500 | 19.050 |
| 49/64 in | 0.7656 | 19.447 |
| 25/32 in | 0.7812 | 19.844 |
| 51/64 in | 0.7969 | 20.241 |
| 13/16 in | 0.8125 | 20.637 |
| 53/64 in | 0.8281 | 21.034 |
| 27/32 in | 0.8438 | 21.431 |
| 55/64 in | 0.8594 | 21.828 |
| 7/8 in | 0.8750 | 22.225 |
| 57/64 in | 0.8906 | 22.622 |
| 29/32 in | 0.9062 | 23.019 |
| 59/64 in | 0.9219 | 23.416 |
| 15/16 in | 0.9375 | 23.812 |
| 61/64 in | 0.9531 | 24.209 |
| 31/32 in | 0.9688 | 24.606 |
| 63/64 in | 0.9844 | 25.003 |
| 1 in | 1.0000 | 25.400 |
Number drills run from #1 at 0.2280 in (5.791 mm) down to #80 at 0.0135 in (0.343 mm). A smaller number is a larger bit, which is the part that catches people out.
They are three separate series that overlap in diameter. Letter drills run A to Z, from 0.2340 in to 0.4130 in. Fractional drills step in sixty-fourths from 0.015625 in to 1.0000 in. A letter drill can be the exact size where no fraction or number lands close enough.
A #7 drill. That size is in the number series and appears in the table above; the tap drill chart gives the same answer for every common unified thread.
A drilled hole normally runs a few thousandths over nominal, which is why reaming follows drilling when the tolerance is tight. The tables above give nominal size, not the hole the drill will actually cut.