Drill Bit Size Chart: Inch, Metric, Number & Letter Sizes
May. 29, 2026
Choosing the right drill bit size is essential for accurate holes, clean machining, proper tapping, and reliable fastening. This drill bit size chart provides a practical reference for common metric drill bits, fractional inch drill bits, number drill bits, and letter drill bits used in metalworking, woodworking, construction, maintenance, and industrial production.
Whether you are drilling pilot holes, preparing holes for tapping, or selecting bits for CNC machining, the following drill bit size tables help you quickly compare diameters in inches and millimeters.
Metric Drill Bit Size Chart
Metric drill bits are widely used in industrial manufacturing, machinery repair, automotive work, and general engineering applications.
| Metric Size | Diameter mm | Diameter inch |
| 0.5 mm | 0.5 | 0.0197 |
| 0.6 mm | 0.6 | 0.0236 |
| 0.7 mm | 0.7 | 0.0276 |
| 0.8 mm | 0.8 | 0.0315 |
| 0.9 mm | 0.9 | 0.0354 |
| 1.0 mm | 1 | 0.0394 |
| 1.2 mm | 1.2 | 0.0472 |
| 1.5 mm | 1.5 | 0.0591 |
| 1.8 mm | 1.8 | 0.0709 |
| 2.0 mm | 2 | 0.0787 |
| 2.5 mm | 2.5 | 0.0984 |
| 3.0 mm | 3 | 0.1181 |
| 3.2 mm | 3.2 | 0.126 |
| 3.5 mm | 3.5 | 0.1378 |
| 4.0 mm | 4 | 0.1575 |
| 4.2 mm | 4.2 | 0.1654 |
| 4.5 mm | 4.5 | 0.1772 |
| 5.0 mm | 5 | 0.1969 |
| 5.5 mm | 5.5 | 0.2165 |
| 6.0 mm | 6 | 0.2362 |
| 6.5 mm | 6.5 | 0.2559 |
| 7.0 mm | 7 | 0.2756 |
| 7.5 mm | 7.5 | 0.2953 |
| 8.0 mm | 8 | 0.315 |
| 8.5 mm | 8.5 | 0.3346 |
| 9.0 mm | 9 | 0.3543 |
| 9.5 mm | 9.5 | 0.374 |
| 10.0 mm | 10 | 0.3937 |
| 10.5 mm | 10.5 | 0.4134 |
| 11.0 mm | 11 | 0.4331 |
| 11.5 mm | 11.5 | 0.4528 |
| 12.0 mm | 12 | 0.4724 |
| 12.5 mm | 12.5 | 0.4921 |
| 13.0 mm | 13 | 0.5118 |
Fractional Inch Drill Bit Size Chart
Fractional inch drill bits are commonly used in North America for general drilling, maintenance, fabrication, and construction work.
| Fractional Size | Decimal inch | Diameter mm |
| 1/64" | 0.0156 | 0.397 |
| 1/32" | 0.0313 | 0.794 |
| 3/64" | 0.0469 | 1.191 |
| 1/16" | 0.0625 | 1.588 |
| 5/64" | 0.0781 | 1.984 |
| 3/32" | 0.0938 | 2.381 |
| 7/64" | 0.1094 | 2.778 |
| 1/8" | 0.125 | 3.175 |
| 9/64" | 0.1406 | 3.572 |
| 5/32" | 0.1563 | 3.969 |
| 11/64" | 0.1719 | 4.366 |
| 3/16" | 0.1875 | 4.763 |
| 13/64" | 0.2031 | 5.159 |
| 7/32" | 0.2188 | 5.556 |
| 15/64" | 0.2344 | 5.953 |
| 1/4" | 0.25 | 6.35 |
| 17/64" | 0.2656 | 6.747 |
| 9/32" | 0.2813 | 7.144 |
| 19/64" | 0.2969 | 7.541 |
| 5/16" | 0.3125 | 7.938 |
| 21/64" | 0.3281 | 8.334 |
| 11/32" | 0.3438 | 8.731 |
| 23/64" | 0.3594 | 9.128 |
| 3/8" | 0.375 | 9.525 |
| 25/64" | 0.3906 | 9.922 |
| 13/32" | 0.4063 | 10.319 |
| 27/64" | 0.4219 | 10.716 |
| 7/16" | 0.4375 | 11.113 |
| 29/64" | 0.4531 | 11.509 |
| 15/32" | 0.4688 | 11.906 |
| 31/64" | 0.4844 | 12.303 |
| 1/2" | 0.5 | 12.7 |
Number Drill Bit Size Chart
Number drill bits are often used for precision drilling, tapping preparation, electronics, aerospace, and metalworking applications.
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| Number Size | Decimal inch | Diameter mm |
| #80 | 0.0135 | 0.343 |
| #79 | 0.0145 | 0.368 |
| #78 | 0.016 | 0.406 |
| #77 | 0.018 | 0.457 |
| #76 | 0.02 | 0.508 |
| #75 | 0.021 | 0.533 |
| #74 | 0.0225 | 0.572 |
| #73 | 0.024 | 0.61 |
| #72 | 0.025 | 0.635 |
| #71 | 0.026 | 0.66 |
| #70 | 0.028 | 0.711 |
| #69 | 0.0292 | 0.742 |
| #68 | 0.031 | 0.787 |
| #67 | 0.032 | 0.813 |
| #66 | 0.033 | 0.838 |
| #65 | 0.035 | 0.889 |
| #64 | 0.036 | 0.914 |
| #63 | 0.037 | 0.94 |
| #62 | 0.038 | 0.965 |
| #61 | 0.039 | 0.991 |
| #60 | 0.04 | 1.016 |
| #59 | 0.041 | 1.041 |
| #58 | 0.042 | 1.067 |
| #57 | 0.043 | 1.092 |
| #56 | 0.0465 | 1.181 |
| #55 | 0.052 | 1.321 |
| #54 | 0.055 | 1.397 |
| #53 | 0.0595 | 1.511 |
| #52 | 0.0635 | 1.613 |
| #51 | 0.067 | 1.702 |
| #50 | 0.07 | 1.778 |
| #49 | 0.073 | 1.854 |
| #48 | 0.076 | 1.93 |
| #47 | 0.0785 | 1.994 |
| #46 | 0.081 | 2.057 |
| #45 | 0.082 | 2.083 |
| #44 | 0.086 | 2.184 |
| #43 | 0.089 | 2.261 |
| #42 | 0.0935 | 2.375 |
| #41 | 0.096 | 2.438 |
| #40 | 0.098 | 2.489 |
| #39 | 0.0995 | 2.527 |
| #38 | 0.1015 | 2.578 |
| #37 | 0.104 | 2.642 |
| #36 | 0.1065 | 2.705 |
| #35 | 0.11 | 2.794 |
| #34 | 0.111 | 2.819 |
| #33 | 0.113 | 2.87 |
| #32 | 0.116 | 2.946 |
| #31 | 0.12 | 3.048 |
| #30 | 0.1285 | 3.264 |
| #29 | 0.136 | 3.454 |
| #28 | 0.1405 | 3.569 |
| #27 | 0.144 | 3.658 |
| #26 | 0.147 | 3.734 |
| #25 | 0.1495 | 3.797 |
| #24 | 0.152 | 3.861 |
| #23 | 0.154 | 3.912 |
| #22 | 0.157 | 3.988 |
| #21 | 0.159 | 4.039 |
| #20 | 0.161 | 4.089 |
| #19 | 0.166 | 4.216 |
| #18 | 0.1695 | 4.305 |
| #17 | 0.173 | 4.394 |
| #16 | 0.177 | 4.496 |
| #15 | 0.18 | 4.572 |
| #14 | 0.182 | 4.623 |
| #13 | 0.185 | 4.699 |
| #12 | 0.189 | 4.801 |
| #11 | 0.191 | 4.851 |
| #10 | 0.1935 | 4.915 |
| #9 | 0.196 | 4.978 |
| #8 | 0.199 | 5.055 |
| #7 | 0.201 | 5.105 |
| #6 | 0.204 |
