Drill Size Chart
Reference chart of drill sizes including metric, fractional, and letter sizes for precise hole drilling
Drill Size Chart
| Drill Size | Metric (mm) | Inch (decimal) |
|---|---|---|
| 1 | 7.0 | 0.2760 |
| 2 | 6.54 | 0.2570 |
| 3 | 6.35 | 0.2500 |
| 4 | 6.02 | 0.2370 |
| 5 | 5.69 | 0.2240 |
| 6 | 5.18 | 0.2040 |
| 7 | 4.95 | 0.1950 |
| 8 | 4.75 | 0.1870 |
| 9 | 4.57 | 0.1800 |
| 10 | 4.47 | 0.1760 |
| 11 | 4.27 | 0.1680 |
| 12 | 4.07 | 0.1600 |
| 13 | 3.91 | 0.1540 |
| 14 | 3.76 | 0.1480 |
| 15 | 3.56 | 0.1400 |
| 16 | 3.45 | 0.1360 |
| 17 | 3.35 | 0.1320 |
| 18 | 3.27 | 0.1290 |
| 19 | 3.20 | 0.1260 |
| 20 | 3.02 | 0.1190 |
| 21 | 2.92 | 0.1150 |
| 22 | 2.82 | 0.1110 |
| 23 | 2.72 | 0.1070 |
| 24 | 2.66 | 0.1040 |
| 25 | 2.54 | 0.1000 |
| 26 | 2.46 | 0.0970 |
| 27 | 2.38 | 0.0940 |
| 28 | 2.34 | 0.0920 |
| 29 | 2.29 | 0.0900 |
| 30 | 2.22 | 0.0870 |
| 31 | 2.16 | 0.0850 |
| 32 | 2.11 | 0.0830 |
| 33 | 2.05 | 0.0810 |
| 34 | 2.0 | 0.0790 |
| 35 | 1.95 | 0.0770 |
| 36 | 1.91 | 0.0750 |
| 37 | 1.86 | 0.0730 |
| 38 | 1.81 | 0.0710 |
| 39 | 1.78 | 0.0700 |
| 40 | 1.73 | 0.0680 |
| 41 | 1.70 | 0.0670 |
| 42 | 1.65 | 0.0650 |
| 43 | 1.60 | 0.0630 |
| 44 | 1.55 | 0.0610 |
| 45 | 1.52 | 0.0600 |
| 46 | 1.50 | 0.0590 |
| 47 | 1.45 | 0.0570 |
| 48 | 1.40 | 0.0550 |
| 49 | 1.35 | 0.0530 |
| 50 | 1.30 | 0.0510 |
| 51 | 1.25 | 0.0490 |
| 52 | 1.20 | 0.0470 |
| 53 | 1.18 | 0.0465 |
| 54 | 1.12 | 0.0440 |
| 55 | 1.08 | 0.0425 |
| 56 | 1.05 | 0.0415 |
| 57 | 1.02 | 0.0400 |
| 58 | 1.0 | 0.0394 |
| 59 | 0.98 | 0.0386 |
| 60 | 0.95 | 0.0374 |
| 61 | 0.93 | 0.0366 |
| 62 | 0.90 | 0.0354 |
| 63 | 0.88 | 0.0346 |
| 64 | 0.86 | 0.0338 |
| 65 | 0.84 | 0.0330 |
| 66 | 0.82 | 0.0323 |
| 67 | 0.80 | 0.0315 |
| 68 | 0.79 | 0.0311 |
| 69 | 0.77 | 0.0303 |
| 70 | 0.76 | 0.0299 |
| 71 | 0.74 | 0.0291 |
| 72 | 0.73 | 0.0287 |
| 73 | 0.71 | 0.0280 |
| 74 | 0.70 | 0.0276 |
| 75 | 0.68 | 0.0268 |
| 76 | 0.66 | 0.0260 |
| 77 | 0.65 | 0.0256 |
| 78 | 0.64 | 0.0252 |
| 79 | 0.63 | 0.0248 |
| 80 | 0.62 | 0.0244 |
| A | 6.50 | 0.2560 |
| B | 6.60 | 0.2600 |
| C | 6.75 | 0.2660 |
| D | 6.85 | 0.2700 |
| E | 7.00 | 0.2760 |
| F | 7.15 | 0.2810 |
| G | 7.30 | 0.2870 |
| H | 7.45 | 0.2930 |
| I | 7.60 | 0.2990 |
| J | 7.75 | 0.3050 |
| K | 7.90 | 0.3110 |
| L | 8.05 | 0.3170 |
| M | 8.20 | 0.3230 |
| N | 8.35 | 0.3290 |
| O | 8.50 | 0.3350 |
| P | 8.65 | 0.3410 |
| Q | 8.80 | 0.3460 |
| R | 8.95 | 0.3520 |
| S | 9.10 | 0.3580 |
| T | 9.25 | 0.3640 |
| U | 9.40 | 0.3700 |
| V | 9.55 | 0.3760 |
| W | 9.70 | 0.3820 |
| X | 9.85 | 0.3880 |
| Y | 10.00 | 0.3940 |
| Z | 10.15 | 0.4000 |
| 1/64" | 0.3969 | 0.0156 |
| 1/32" | 0.7938 | 0.0313 |
| 3/64" | 1.1906 | 0.0469 |
| 1/16" | 1.5880 | 0.0625 |
| 5/64" | 1.5875 | 0.0781 |
| 3/32" | 2.3813 | 0.0938 |
| 7/64" | 2.7781 | 0.1094 |
| 1/8" | 3.1750 | 0.1250 |
| 9/64" | 3.5719 | 0.1406 |
| 5/32" | 3.9688 | 0.1563 |
| 11/64" | 4.3656 | 0.1719 |
| 3/16" | 4.7625 | 0.1875 |
| 13/64" | 5.1594 | 0.2031 |
| 7/32" | 5.5563 | 0.2188 |
| 15/64" | 5.9531 | 0.2344 |
| 1/4" | 6.3500 | 0.2500 |
| 17/64" | 6.7469 | 0.2656 |
| 9/32" | 7.1438 | 0.2813 |
| 19/64" | 7.5406 | 0.2969 |
| 5/16" | 7.9375 | 0.3125 |
| 21/64" | 8.3344 | 0.3281 |
| 11/32" | 8.7313 | 0.3438 |
| 23/64" | 9.1281 | 0.3594 |
| 3/8" | 9.5250 | 0.3750 |
| 25/64" | 9.9219 | 0.3906 |
| 13/32" | 10.3188 | 0.4063 |
| 27/64" | 10.7156 | 0.4219 |
| 7/16" | 11.1125 | 0.4375 |
| 29/64" | 11.5094 | 0.4531 |
| 15/32" | 11.9063 | 0.4688 |
| 31/64" | 12.3031 | 0.4844 |
| 1/2" | 12.7000 | 0.5000 |
| 33/64" | 13.0969 | 0.5156 |
| 17/32" | 13.4938 | 0.5313 |
| 35/64" | 13.8906 | 0.5469 |
| 9/16" | 14.2875 | 0.5625 |
| 37/64" | 14.6844 | 0.5781 |
| 19/32" | 15.0813 | 0.5938 |
| 39/64" | 15.4781 | 0.6094 |
| 5/8" | 15.8750 | 0.6250 |
| 41/64" | 16.2719 | 0.6406 |
| 21/32" | 16.6688 | 0.6563 |
| 43/64" | 17.0656 | 0.6719 |
| 7/8" | 17.4625 | 0.6875 |
| 45/64" | 17.8594 | 0.7031 |
| 23/32" | 18.2563 | 0.7188 |
| 47/64" | 18.6531 | 0.7344 |
| 15/16" | 19.0500 | 0.7500 |
| 49/64" | 19.4469 | 0.7656 |
| 25/32" | 19.8438 | 0.7813 |
| 51/64" | 20.2406 | 0.7969 |
| 1" | 25.4000 | 1.0000 |
About Drill Size Chart & Hole Diameter Reference
This comprehensive drill size chart provides standardized data for metric, fractional, letter, and number drill sizes used in engineering, machining, manufacturing, and fabrication. It enables precise selection of drill bits for accurate hole diameters in metalworking, woodworking, and mechanical design applications.
Understanding drill bit dimensions and tolerances ensures proper hole sizing, reliable fastener fit, and consistent machining quality. This chart supports standardized manufacturing practices and helps engineers, machinists, and designers maintain dimensional accuracy in components requiring tight tolerances or threaded connections.
Drill Size Definitions
- Metric Drill Sizes (mm) – Based on ISO and DIN standards, used globally for precision drilling in industrial and engineering applications.
- Fractional Drill Sizes (inches) – Inch-based drill diameters common in North America for construction, machining, and woodworking.
- Letter Drill Sizes (A–Z) – Alphabetical series of drills used for intermediate diameters and tight-tolerance hole preparation.
- Number Drill Sizes (#1–#80) – Small, numbered drills used for fine or precision holes in metal, electronics, and mechanical design.
- Drill Tolerances – Actual hole size may vary slightly depending on tool wear, material hardness, and machine accuracy; gauges should be used for inspection.
Applications and Engineering Use
The drill size reference chart is an essential tool in mechanical engineering, product design, CNC machining, and toolmaking. It assists users in selecting the correct drill for:
- Creating accurate pilot holes for screws, bolts, and fasteners
- Matching tapping drill sizes for internal threads
- Ensuring proper fit and clearance in mechanical assemblies
- Maintaining precision in metal, plastic, and wood fabrication
By referencing standardized drill size dimensions, engineers and manufacturers can ensure repeatable results, improve assembly accuracy, and achieve consistent hole tolerances and surface finishes. This dataset supports precision design, quality control, and efficient production across diverse engineering disciplines.