Use this drill bit size chart to cross-reference metric (mm), imperial (fractional and decimal inches), and gauge sizes — including number and letter — in a single reference table. Whether you're sizing a pilot hole for a screw or bolt, converting between measurement systems, or identifying an unmarked bit, find your size below and read across the row for the equivalent.
Not sure which bit to use? See our Choosing the Right Drill Bit: A Complete Guide for Metal, Wood, Masonry & More for material-by-material guidance on bit type, coating, speed settings, and the most common mistakes to avoid.
How to Use This Chart
The table covers drill bit sizes from 0.010mm to 25.4mm (1 inch). Find your required hole size in the metric or imperial column and read across to identify the equivalent gauge number, letter, fractional, or decimal size.
A few things to keep in mind. Not all metric drill bits have imperial equivalents and vice versa. Some metric values are close enough to share the same imperial counterpart. Values are rounded to the nearest thousandth millimetre or ten-thousandth decimal inch.
| Gauge Sizing | Metric / SI | Imperial / US | ||
| Number / Letter Size | Millimeters | Fractional Inches | Fractional Inches (Reduced) | Decimal Inches |
| --- | 0.010 | --- | --- | 0.0004 |
| 104 | 0.080 | --- | --- | 0.0031 |
| 103 | 0.090 | --- | --- | 0.0035 |
| 102 | --- | --- | --- | 0.0039 |
| --- | 0.100 | --- | --- | 0.0039 |
| 101 | 0.110 | --- | --- | 0.0043 |
| 100 | 0.120 | --- | --- | 0.0047 |
| 99 | 0.130 | --- | --- | 0.0051 |
| 98 | 0.140 | --- | --- | 0.0055 |
| 97 | 0.150 | --- | --- | 0.0059 |
| 96 | 0.160 | --- | --- | 0.0063 |
| 95 | 0.170 | --- | --- | 0.0067 |
| 94 | 0.180 | --- | --- | 0.0071 |
| 93 | 0.190 | --- | --- | 0.0075 |
| --- | 0.198 | 1/128 | --- | 0.0078 |
| 92 | 0.201 | --- | --- | 0.0079 |
| 91 | 0.210 | --- | --- | 0.0083 |
| 90 | 0.220 | --- | --- | 0.0087 |
| 89 | 0.230 | --- | --- | 0.0091 |
| 88 | 0.240 | --- | --- | 0.0095 |
| --- | 0.250 | --- | --- | 0.0098 |
| 87 | 0.254 | --- | --- | 0.0100 |
| --- | 0.260 | --- | --- | 0.0102 |
| 86 | 0.270 | --- | --- | 0.0105 |
| 85 | 0.280 | --- | --- | 0.0110 |
| 84 | 0.290 | --- | --- | 0.0115 |
| --- | 0.300 | --- | --- | 0.0118 |
| 83 | 0.305 | --- | --- | 0.0120 |
| 82 | 0.318 | --- | --- | 0.0125 |
| 81 | 0.330 | --- | --- | 0.0130 |
| 80 | 0.343 | --- | --- | 0.0135 |
| 79 | 0.368 | --- | --- | 0.0145 |
| --- | 0.397 | 1/64 | --- | 0.0156 |
| 78 | 0.406 | --- | --- | 0.0160 |
| 77 | 0.457 | --- | --- | 0.0180 |
| --- | 0.500 | --- | --- | 0.0197 |
| 76 | 0.508 | --- | --- | 0.0200 |
| 75 | 0.533 | --- | --- | 0.0210 |
| 74 | 0.572 | --- | --- | 0.0225 |
| 73 | 0.610 | --- | --- | 0.0240 |
| 72 | 0.635 | --- | --- | 0.0250 |
| 71 | 0.660 | --- | --- | 0.0260 |
| 70 | 0.710 | --- | --- | 0.0280 |
| 69 | 0.742 | --- | --- | 0.0292 |
| --- | 0.750 | --- | --- | 0.0295 |
| 68 | 0.787 | --- | --- | 0.0310 |
| --- | 0.794 | 2/64 | 1/32 | 0.0312 |
| 67 | 0.813 | --- | --- | 0.0320 |
| 66 | 0.838 | --- | --- | 0.0330 |
| 65 | 0.889 | --- | --- | 0.0350 |
| 64 | 0.914 | --- | --- | 0.0360 |
| 63 | 0.940 | --- | --- | 0.0370 |
| 62 | 0.965 | --- | --- | 0.0380 |
| 61 | 0.991 | --- | --- | 0.0390 |
| --- | 1.000 | --- | --- | 0.0394 |
| 60 | 1.016 | --- | --- | 0.0400 |
| 59 | 1.041 | --- | --- | 0.0410 |
| 58 | 1.067 | --- | --- | 0.0420 |
| 57 | 1.092 | --- | --- | 0.0430 |
| 56 | 1.181 | --- | --- | 0.0465 |
| --- | 1.191 | 3/64 | --- | 0.0469 |
| --- | 1.250 | --- | --- | 0.0492 |
| 55 | 1.321 | --- | --- | 0.0520 |
| 54 | 1.397 | --- | --- | 0.0550 |
| --- | 1.500 | --- | --- | 0.0591 |
| 53 | 1.511 | --- | --- | 0.0595 |
| --- | 1.588 | 4/64 | 1/16 | 0.0625 |
| 52 | 1.613 | --- | --- | 0.0635 |
| 51 | 1.702 | --- | --- | 0.0670 |
| --- | 1.750 | --- | --- | 0.0689 |
| 50 | 1.778 | --- | --- | 0.0700 |
| --- | 1.800 | --- | --- | 0.0709 |
| --- | 1.850 | --- | --- | 0.0728 |
| 49 | 1.854 | --- | --- | 0.0730 |
| 48 | 1.930 | --- | --- | 0.0760 |
| --- | 1.984 | 5/64 | --- | 0.0781 |
| 47 | 1.994 | --- | --- | 0.0785 |
| --- | 2.000 | --- | --- | 0.0787 |
| 46 | 2.057 | --- | --- | 0.0810 |
| 45 | 2.083 | --- | --- | 0.0820 |
| 44 | 2.184 | --- | --- | 0.0860 |
| --- | 2.250 | --- | --- | 0.0886 |
| 43 | 2.261 | --- | --- | 0.0890 |
| 42 | 2.375 | --- | --- | 0.0935 |
| --- | 2.381 | 6/64 | 3/32 | 0.0938 |
| 41 | 2.438 | --- | --- | 0.0960 |
| --- | 2.450 | --- | --- | 0.0965 |
| 40 | 2.489 | --- | --- | 0.0980 |
| --- | 2.500 | --- | --- | 0.0984 |
| 39 | 2.527 | --- | --- | 0.0995 |
| 38 | 2.578 | --- | --- | 0.1015 |
| 37 | 2.642 | --- | --- | 0.1040 |
| 36 | 2.705 | --- | --- | 0.1065 |
| --- | 2.750 | --- | --- | 0.1083 |
| --- | 2.778 | 7/64 | --- | 0.1094 |
| 35 | 2.794 | --- | --- | 0.1100 |
| 34 | 2.819 | --- | --- | 0.1110 |
| 33 | 2.870 | --- | --- | 0.1130 |
| 32 | 2.946 | --- | --- | 0.1160 |
| --- | 3.000 | --- | --- | 0.1181 |
| 31 | 3.048 | --- | --- | 0.1200 |
| --- | 3.175 | 8/64 | 1/8 | 0.1250 |
| --- | 3.250 | --- | --- | 0.1280 |
| 30 | 3.264 | --- | --- | 0.1285 |
| 29 | 3.454 | --- | --- | 0.1360 |
| --- | 3.500 | --- | --- | 0.1378 |
| 28 | 3.569 | --- | --- | 0.1405 |
| --- | 3.572 | 9/64 | --- | 0.1406 |
| 27 | 3.658 | --- | --- | 0.1440 |
| 26 | 3.734 | --- | --- | 0.1470 |
| --- | 3.750 | --- | --- | 0.1476 |
| 25 | 3.797 | --- | --- | 0.1495 |
| 24 | 3.861 | --- | --- | 0.1520 |
| 23 | 3.912 | --- | --- | 0.1540 |
| --- | 3.969 | 10/64 | 5/32 | 0.1562 |
| 22 | 3.988 | --- | --- | 0.1570 |
| --- | 4.000 | --- | --- | 0.1575 |
| 21 | 4.039 | --- | --- | 0.1590 |
| 20 | 4.089 | --- | --- | 0.1610 |
| 19 | 4.216 | --- | --- | 0.1660 |
| --- | 4.250 | --- | --- | 0.1673 |
| 18 | 4.305 | --- | --- | 0.1695 |
| --- | 4.366 | 11/64 | --- | 0.1720 |
| 17 | 4.394 | --- | --- | 0.1730 |
| 16 | 4.496 | --- | --- | 0.1770 |
| --- | 4.500 | --- | --- | 0.1772 |
| 15 | 4.572 | --- | --- | 0.1800 |
| 14 | 4.623 | --- | --- | 0.1820 |
| 13 | 4.469 | --- | --- | 0.1850 |
| --- | 4.750 | --- | --- | 0.1870 |
| --- | 4.763 | 12/64 | 3/16 | 0.1875 |
| 12 | 4.800 | --- | --- | 0.1890 |
| 11 | 4.850 | --- | --- | 0.1910 |
| 10 | 4.915 | --- | --- | 0.1935 |
| 9 | 4.978 | |||
