Reference chart
Drill size chart
Decimal-inch and millimetre equivalents for fractional, number and letter drill sizes. For the hole to drill before tapping a thread, use the tap drill size calculator.
Fractional drill sizes
| Fraction | Decimal (in) | mm |
|---|---|---|
| 1/64" | 0.0156 | 0.40 |
| 1/32" | 0.0313 | 0.79 |
| 3/64" | 0.0469 | 1.19 |
| 1/16" | 0.0625 | 1.59 |
| 5/64" | 0.0781 | 1.98 |
| 3/32" | 0.0938 | 2.38 |
| 7/64" | 0.1094 | 2.78 |
| 1/8" | 0.1250 | 3.17 |
| 9/64" | 0.1406 | 3.57 |
| 5/32" | 0.1563 | 3.97 |
| 11/64" | 0.1719 | 4.37 |
| 3/16" | 0.1875 | 4.76 |
| 13/64" | 0.2031 | 5.16 |
| 7/32" | 0.2188 | 5.56 |
| 15/64" | 0.2344 | 5.95 |
| 1/4" | 0.2500 | 6.35 |
| 17/64" | 0.2656 | 6.75 |
| 9/32" | 0.2813 | 7.14 |
| 19/64" | 0.2969 | 7.54 |
| 5/16" | 0.3125 | 7.94 |
| 21/64" | 0.3281 | 8.33 |
| 11/32" | 0.3438 | 8.73 |
| 23/64" | 0.3594 | 9.13 |
| 3/8" | 0.3750 | 9.52 |
| 25/64" | 0.3906 | 9.92 |
| 13/32" | 0.4063 | 10.32 |
| 27/64" | 0.4219 | 10.72 |
| 7/16" | 0.4375 | 11.11 |
| 29/64" | 0.4531 | 11.51 |
| 15/32" | 0.4688 | 11.91 |
| 31/64" | 0.4844 | 12.30 |
| 1/2" | 0.5000 | 12.70 |
Number drill sizes (#1 to #40)
| Size | Decimal (in) | mm |
|---|---|---|
| #1 | 0.2280 | 5.79 |
| #2 | 0.2210 | 5.61 |
| #3 | 0.2130 | 5.41 |
| #4 | 0.2090 | 5.31 |
| #5 | 0.2055 | 5.22 |
| #6 | 0.2040 | 5.18 |
| #7 | 0.2010 | 5.11 |
| #8 | 0.1990 | 5.05 |
| #9 | 0.1960 | 4.98 |
| #10 | 0.1935 | 4.91 |
| #11 | 0.1910 | 4.85 |
| #12 | 0.1890 | 4.80 |
| #13 | 0.1850 | 4.70 |
| #14 | 0.1820 | 4.62 |
| #15 | 0.1800 | 4.57 |
| #16 | 0.1770 | 4.50 |
| #17 | 0.1730 | 4.39 |
| #18 | 0.1695 | 4.31 |
| #19 | 0.1660 | 4.22 |
| #20 | 0.1610 | 4.09 |
| #21 | 0.1590 | 4.04 |
| #22 | 0.1570 | 3.99 |
| #23 | 0.1540 | 3.91 |
| #24 | 0.1520 | 3.86 |
| #25 | 0.1495 | 3.80 |
| #26 | 0.1470 | 3.73 |
| #27 | 0.1440 | 3.66 |
| #28 | 0.1405 | 3.57 |
| #29 | 0.1360 | 3.45 |
| #30 | 0.1285 | 3.26 |
| #31 | 0.1200 | 3.05 |
| #32 | 0.1160 | 2.95 |
| #33 | 0.1130 | 2.87 |
| #34 | 0.1110 | 2.82 |
| #35 | 0.1100 | 2.79 |
| #36 | 0.1065 | 2.71 |
| #37 | 0.1040 | 2.64 |
| #38 | 0.1015 | 2.58 |
| #39 | 0.0995 | 2.53 |
| #40 | 0.0980 | 2.49 |
Letter drill sizes (A to Z)
| Size | Decimal (in) | mm |
|---|---|---|
| A | 0.2340 | 5.94 |
| B | 0.2380 | 6.05 |
| C | 0.2420 | 6.15 |
| D | 0.2460 | 6.25 |
| E | 0.2500 | 6.35 |
| F | 0.2570 | 6.53 |
| G | 0.2610 | 6.63 |
| H | 0.2660 | 6.76 |
| I | 0.2720 | 6.91 |
| J | 0.2770 | 7.04 |
| K | 0.2810 | 7.14 |
| L | 0.2900 | 7.37 |
| M | 0.2950 | 7.49 |
| N | 0.3020 | 7.67 |
| O | 0.3160 | 8.03 |
| P | 0.3230 | 8.20 |
| Q | 0.3320 | 8.43 |
| R | 0.3390 | 8.61 |
| S | 0.3480 | 8.84 |
| T | 0.3580 | 9.09 |
| U | 0.3680 | 9.35 |
| V | 0.3770 | 9.58 |
| W | 0.3860 | 9.80 |
| X | 0.3970 | 10.08 |
| Y | 0.4040 | 10.26 |
| Z | 0.4130 | 10.49 |
Number and letter sizes are the standard published decimal equivalents; fractional sizes are exact (the fraction times one inch). Millimetre values are the decimal inch times 25.4.