Guides / Shop charts · Updated
Drill bit size chart
Decimal sizes from Drill America's chart, cross-checked against Irwin's. Millimeters are 25.4 to the inch.
Short answer
Number drills run backwards: #1 is the biggest at .2280 in and #60 the smallest at .0400. Letter drills pick up above that, from A (.2340) to Z (.4130). Fractional drills go in 64ths: 1/4 in is .2500.
Fractional drills, 1/64 to 1/2 in
| Drill | Inches | mm |
|---|---|---|
| 1/64 | .0156 | 0.40 |
| 1/32 | .0312 | 0.79 |
| 3/64 | .0469 | 1.19 |
| 1/16 | .0625 | 1.59 |
| 5/64 | .0781 | 1.98 |
| 3/32 | .0938 | 2.38 |
| 7/64 | .1094 | 2.78 |
| 1/8 | .1250 | 3.17 |
| 9/64 | .1406 | 3.57 |
| 5/32 | .1562 | 3.97 |
| 11/64 | .1719 | 4.37 |
| 3/16 | .1875 | 4.76 |
| 13/64 | .2031 | 5.16 |
| 7/32 | .2188 | 5.56 |
| 15/64 | .2344 | 5.95 |
| 1/4 | .2500 | 6.35 |
| 17/64 | .2656 | 6.75 |
| 9/32 | .2812 | 7.14 |
| 19/64 | .2969 | 7.54 |
| 5/16 | .3125 | 7.94 |
| 21/64 | .3281 | 8.33 |
| 11/32 | .3438 | 8.73 |
| 23/64 | .3594 | 9.13 |
| 3/8 | .3750 | 9.52 |
| 25/64 | .3906 | 9.92 |
| 13/32 | .4062 | 10.32 |
| 27/64 | .4219 | 10.72 |
| 7/16 | .4375 | 11.11 |
| 29/64 | .4531 | 11.51 |
| 15/32 | .4688 | 11.91 |
| 31/64 | .4844 | 12.30 |
| 1/2 | .5000 | 12.70 |
Number drills, #1 to #60
| Drill | Inches | mm |
|---|---|---|
| #1 | .2280 | 5.79 |
| #2 | .2210 | 5.61 |
| #3 | .2130 | 5.41 |
| #4 | .2090 | 5.31 |
| #5 | .2055 | 5.22 |
| #6 | .2040 | 5.18 |
| #7 | .2010 | 5.11 |
| #8 | .1990 | 5.05 |
| #9 | .1960 | 4.98 |
| #10 | .1935 | 4.91 |
| #11 | .1910 | 4.85 |
| #12 | .1890 | 4.80 |
| #13 | .1850 | 4.70 |
| #14 | .1820 | 4.62 |
| #15 | .1800 | 4.57 |
| #16 | .1770 | 4.50 |
| #17 | .1730 | 4.39 |
| #18 | .1695 | 4.31 |
| #19 | .1660 | 4.22 |
| #20 | .1610 | 4.09 |
| #21 | .1590 | 4.04 |
| #22 | .1570 | 3.99 |
| #23 | .1540 | 3.91 |
| #24 | .1520 | 3.86 |
| #25 | .1495 | 3.80 |
| #26 | .1470 | 3.73 |
| #27 | .1440 | 3.66 |
| #28 | .1405 | 3.57 |
| #29 | .1360 | 3.45 |
| #30 | .1285 | 3.26 |
| #31 | .1200 | 3.05 |
| #32 | .1160 | 2.95 |
| #33 | .1130 | 2.87 |
| #34 | .1110 | 2.82 |
| #35 | .1100 | 2.79 |
| #36 | .1065 | 2.71 |
| #37 | .1040 | 2.64 |
| #38 | .1015 | 2.58 |
| #39 | .0995 | 2.53 |
| #40 | .0980 | 2.49 |
| #41 | .0960 | 2.44 |
| #42 | .0935 | 2.37 |
| #43 | .0890 | 2.26 |
| #44 | .0860 | 2.18 |
| #45 | .0820 | 2.08 |
| #46 | .0810 | 2.06 |
| #47 | .0785 | 1.99 |
| #48 | .0760 | 1.93 |
| #49 | .0730 | 1.85 |
| #50 | .0700 | 1.78 |
| #51 | .0670 | 1.70 |
| #52 | .0635 | 1.61 |
| #53 | .0595 | 1.51 |
| #54 | .0550 | 1.40 |
| #55 | .0520 | 1.32 |
| #56 | .0465 | 1.18 |
| #57 | .0430 | 1.09 |
| #58 | .0420 | 1.07 |
| #59 | .0410 | 1.04 |
| #60 | .0400 | 1.02 |
Letter drills, A to Z
| Drill | Inches | mm |
|---|---|---|
| A | .2340 | 5.94 |
| B | .2380 | 6.05 |
| C | .2420 | 6.15 |
| D | .2460 | 6.25 |
| E | .2500 | 6.35 |
| F | .2570 | 6.53 |
| G | .2610 | 6.63 |
| H | .2660 | 6.76 |
| I | .2720 | 6.91 |
| J | .2770 | 7.04 |
| K | .2810 | 7.14 |
| L | .2900 | 7.37 |
| M | .2950 | 7.49 |
| N | .3020 | 7.67 |
| O | .3160 | 8.03 |
| P | .3230 | 8.20 |
| Q | .3320 | 8.43 |
| R | .3390 | 8.61 |
| S | .3480 | 8.84 |
| T | .3580 | 9.09 |
| U | .3680 | 9.35 |
| V | .3770 | 9.58 |
| W | .3860 | 9.80 |
| X | .3970 | 10.08 |
| Y | .4040 | 10.26 |
| Z | .4130 | 10.49 |
Drilling for a tap?
The tap drill chart lists the drill for each thread. For converting tape-measure fractions, see the fraction to decimal chart.