Drill Bit Size Conversion Table
Drill bits from zero to one half inch are sized in four ways; fractions, wire gauge numbers, letters, and metric in millimeters. You will see drill bits with a fraction, number, letter or metric number stamped on their shank indicating their size.
The fractions range from 1/64 inch to 32/64 inch. The numbers range from 107 (smallest) to 1 (largest). Where the number 1 drill bit leaves off the letter A (smallest) begins and continues through the letter Z (largest).
The metric sizes are dispersed throughout. All of these drill bits are different in size except for the 90 and .22mm which are both 0.0087 inches in diameter, the 85 and the .28mm which are both 0.0110 inches in diameter, the 13 and the 4.7mm which are both 0.1850 inches in diameter, the 4.8mm and the 12 which are both 0.1890 inches in diameter, and the 1/4 inch and letter E bits which are both 0.250 inches in diameter.
All of the drill bits are listed below with their decimal equivalents.
Drill Bit Decimal Decimal Size (in.) (mm) 107 0.0019 0.0483 106 0.0023 0.0584 105 0.0027 0.0686 104 0.0031 0.0787 103 0.0035 0.0889 102 0.0039 0.0991 101 0.0043 0.1092 100 0.0047 0.1194 99 0.0051 0.1295 98 0.0055 0.1397 97 0.0059 0.1499 96 0.0063 0.1600 95 0.0067 0.1702 94 0.0071 0.1803 93 0.0075 0.1905 92 0.0079 0.2007 .2mm 0.0079 0.2007 91 0.0083 0.2108 90 0.0087 0.2210 .22mm 0.0087 0.2210 89 0.0091 0.2311 88 0.0095 0.2413 .25mm 0.0098 0.2489 87 0.0100 0.2540 86 0.0105 0.2667 85 0.0110 0.2794 .28mm 0.0110 0.2794 84 0.0115 0.2921 .3mm 0.0118 0.2997 83 0.0120 0.3048 82 0.0125 0.3175 .32mm 0.0126 0.3200 81 0.0130 0.3302 80 0.0135 0.3429 .35mm 0.0138 0.3505 79 0.0145 0.3683 1/64 0.0156 0.3962 .4mm 0.0157 0.3988 78 0.0160 0.4064 .45mm 0.0177 0.4496 77 0.0180 0.4572 .5mm 0.0197 0.5004 76 0.0200 0.5080 75 0.0210 0.5334 .55mm 0.0217 0.5512 74 0.0225 0.5715 .6mm 0.0236 0.5994 73 0.0240 0.6096 72 0.0250 0.6350 .65mm 0.0256 0.6502 71 0.0260 0.6604 .7mm 0.0276 0.7010 70 0.0280 0.7112 69 0.0292 0.7417 .75mm 0.0295 0.7493 68 0.0310 0.7874 1/32 0.0312 0.7925 .8mm 0.0315 0.8001 67 0.0320 0.8128 66 0.0330 0.8382 .85mm 0.0335 0.8509 65 0.0350 0.8890 .9mm 0.0354 0.8992 64 0.0360 0.9144 63 0.0370 0.9398 .95mm 0.0374 0.9500 62 0.0380 0.9652 61 0.0390 0.9906 1mm 0.0394 1.0008 60 0.0400 1.0160 59 0.0410 1.0414 1.05mm 0.0413 1.0490 58 0.0420 1.0668 57 0.0430 1.0922 1.1mm 0.0433 1.0998 1.15mm 0.0453 1.1506 56 0.0465 1.1811 3/64 0.0469 1.1913 1.2mm 0.0472 1.1989 1.25mm 0.0492 1.2497 1.3mm 0.0512 1.3005 55 0.0520 1.3208 1.35mm 0.0531 1.3487 54 0.0550 1.3970 1.4mm 0.0551 1.3995 1.45mm 0.0571 1.4503 1.5mm 0.0591 1.5011 53 0.0595 1.5113 1.55mm 0.0610 1.5494 1/16 0.0625 1.5875 52 0.0635 1.6129 1.65mm 0.0650 1.6510 1.7mm 0.0669 1.6993 51 0.0670 1.7018 1.75mm 0.0689 1.7501 50 0.0700 1.7780 1.8mm 0.0709 1.8009 1.85mm 0.0728 1.8491 49 0.0730 1.8542 1.9mm 0.0748 1.8999 48 0.0760 1.9304 1.95mm 0.0768 1.9507 5/64 0.0781 1.9837 2mm 0.0787 1.9990 2.05mm 0.0807 2.0498 47 0.0785 1.9939 46 0.0810 2.0574 45 0.0820 2.0828 2.1mm 0.0827 2.1006 2.15mm 0.0846 2.1488 44 0.0860 2.1844 2.2mm 0.0866 2.1996 2.25mm 0.0886 2.2504 43 0.0890 2.2606 2.3mm 0.0906 2.3012 2.35mm 0.0925 2.3495 42 0.0935 2.3749 3/32 0.0938 2.3825 2.4mm 0.0945 2.4003 41 0.0960 2.4384 2.45mm 0.0965 2.4511 40 0.0980 2.4892 2.5mm 0.0984 2.4994 39 0.0995 2.5273 38 0.1015 2.5781 2.6mm 0.1024 2.6010 37 0.1040 2.6416 2.7mm 0.1063 2.7000 36 0.1065 2.7051 2.75mm 0.1083 2.7508 7/64 0.1094 2.7788 35 0.1100 2.7940 2.8mm 0.1102 2.7991 34 0.1110 2.8194 33 0.1130 2.8702 2.9mm 0.1142 2.9007 32 0.1160 2.9464 3mm 0.1181 2.9997 31 0.1200 3.0480 3.1mm 0.1181 2.9997 1/8 0.1250 3.1750 30 0.1285 3.2639 3.3mm 0.1299 3.2995 3.4mm 0.1339 3.4011 29 0.1360 3.4544 3.5mm 0.1378 3.5001 28 0.1405 3.5687 9/64 0.1406 3.5712 3.6mm 0.1417 3.5992 27 0.1440 3.6576 3.7mm 0.1457 3.7008 26 0.1470 3.7338 3.75mm 0.1476 3.7490 25 0.1495 3.7973 3.8mm 0.1535 3.8989 24 0.1520 3.8608 3.9mm 0.1535 3.8989 23 0.1540 3.9116 5/32 0.1562 3.9675 22 0.1570 3.9878 4mm 0.1575 4.0005 21 0.1590 4.0386 20 0.1610 4.0894 4.1mm 0.1614 4.0996 4.2mm 0.1654 4.2012 19 0.1660 4.2164 4.25mm 0.1673 4.2494 4.3mm 0.1693 4.3002 18 0.1695 4.3053 11/64 0.1719 4.3663 17 0.1730 4.3942 4.4mm 0.1732 4.3993 16 0.1770 4.4958 4.5mm 0.1772 4.5009 15 0.1800 4.5720 4.6mm 0.1811 4.5999 14 0.1820 4.6228 13 0.1850 4.6990 4.7mm 0.1850 4.6990 4.75mm 0.1870 4.7498 3/16 0.1875 4.7625 4.8mm 0.1890 4.8006 12 0.1890 4.8006 11 0.1910 4.8514 4.9mm 0.1929 4.8997 10 0.1935 4.9149 9 0.1960 4.9784 5.mm 0.1969 5.0013 8 0.1990 5.0546 5.1mm 0.2008 5.1003 7 0.2010 5.1054 13/64 0.2031 5.1587 6 0.2040 5.1816 5.2mm 0.2047 5.1994 5 0.2055 5.2197 5.25mm 0.2067 5.2502 5.3mm 0.2087 5.3010 4 0.2090 5.3086 5.4mm 0.2126 5.4000 3 0.2130 5.4102 5.5mm 0.2165 5.4991 7/32 0.2188 5.5575 5.6mm 0.2205 5.6007 2 0.2211 5.6159 5.7mm 0.2244 5.6998 5.75mm 0.2264 5.7506 1 0.2280 5.7912 5.8mm 0.2283 5.7988 5.9mm 0.2323 5.9004 A 0.2340 5.9436 15/64 0.2344 5.9538 6mm 0.2362 5.9995 B 0.2380 6.0452 6.1mm 0.2402 6.1011 C 0.2420 6.1468 6.2mm 0.2441 6.2001 D 0.2460 6.2484 6.25mm 0.2461 6.2509 6.3mm 0.2480 6.2992 1/4 0.2500 6.3500 E 0.2500 6.3500 6.4mm 0.2520 6.4008 6.5mm 0.2559 6.4999 F 0.2570 6.5278 6.6mm 0.2598 6.5989 G 0.2610 6.6294 6.7mm 0.2638 6.7005 17/64 0.2656 6.7462 6.75mm 0.2657 6.7488 H 0.2660 6.7564 6.8mm 0.2677 6.7996 6.9mm 0.2717 6.9012 I 0.2720 6.9088 7mm 0.2756 7.0002 J 0.2770 7.0358 7.1mm 0.2795 7.0993 K 0.2810 7.1374 9/32 0.2812 7.1425 7.2mm 0.2835 7.2009 7.25mm 0.2854 7.2492 7.3mm 0.2874 7.3000 L 0.2900 7.3660 7.4mm 0.2913 7.3990 M 0.2950 7.4930 7.5mm 0.2953 7.5006 19/64 0.2969 7.5413 7.6mm 0.2992 7.5997 N 0.3020 7.6708 7.7mm 0.3031 7.6987 7.75mm 0.3051 7.7495 7.8mm 0.3071 7.8003 7.9mm 0.3110 7.8994 5/16 0.3125 7.9375 8mm 0.3150 8.0010 O 0.3160 8.0264 8.1mm 0.3189 8.1001 8.2mm 0.3228 8.1991 P 0.3230 8.2042 8.25mm 0.3248 8.2499 8.3mm 0.3268 8.3007 21/64 0.3281 8.3337 8.4mm 0.3307 8.3998 Q 0.3320 8.4328 8.5mm 0.3346 8.4988 8.6mm 0.3386 8.6004 R 0.3390 8.6106 8.7mm 0.3425 8.6995 11/32 0.3438 8.7325 8.75mm 0.3445 8.7503 8.8mm 0.3465 8.8011 S 0.3480 8.8392 8.9mm 0.3504 8.9002 9mm 0.3543 8.9992 T 0.3580 9.0932 9.1mm 0.3583 9.1008 23/64 0.3594 9.1288 9.2mm 0.3622 9.1999 9.25mm 0.3642 9.2507 9.3mm 0.3661 9.2989 U 0.3680 9.3472 9.4mm 0.3701 9.4005 9.5mm 0.3740 9.4996 3/8 0.3750 9.5250 V 0.3770 9.5758 9.6mm 0.3780 9.6012 9.7mm 0.3819 9.7003 9.75mm 0.3839 9.7511 9.8mm 0.3858 9.7993 W 0.3860 9.8044 9.9mm 0.3898 9.9009 25/64 0.3906 9.9212 10mm 0.3937 10.0000 X 0.3970 10.0838 Y 0.4040 10.2616 13/32 0.4062 10.3175 Z 0.4130 10.4902 10.5mm 0.4134 10.5004 27/64 0.4219 10.7163 11mm 0.4331 11.0007 7/16 0.4375 11.1125 11.5mm 0.4528 11.5011 29/64 0.4531 11.5087 15/32 0.4688 11.9075 12mm 0.4724 11.9990 31/64 0.4844 12.3038 1/2 0.5000 12.7000 13mm 0.5118 12.9997 33/64 0.5156 13.0962 17/32 0.5312 13.4925 13.5mm 0.5315 13.5001 35/64 0.5469 13.8913 14mm 0.5512 14.0005 9/16 0.5625 14.2875 14.5mm 0.5709 14.5009 37/64 0.5781 14.6837 15mm 0.5906 15.0012 19/32 0.5938 15.0825 39/64 0.6094 15.4788 15.5mm 0.6102 15.4991 5/8 0.6250 15.8750 16mm 0.6299 15.9995 41/64 0.6406 16.2712 16.5mm 0.6496 16.4998 21/32 0.6562 16.6675 17mm 0.6693 17.0002 43/64 0.6719 17.0663 11/16 0.6875 17.4625 17.5mm 0.6890 17.5006 45/64 0.7031 17.8587 18mm 0.7087 18.0010 23/32 0.7188 18.2575 18.5mm 0.7283 18.4988 47/64 0.7344 18.6538 19mm 0.7480 18.9992 3/4 0.7500 19.0500 49/64 0.7656 19.4462 19.5mm 0.7677 19.4996 25/32 0.7812 19.8425 20mm 0.7874 20.0000 51/64 0.7969 20.2413 20.5mm 0.8071 20.5003 13/16 0.8125 20.6375 21mm 0.8268 21.0007 53/64 0.8281 21.0337 27/32 0.8438 21.4325 21.5mm 0.8465 21.5011 55/64 0.8594 21.8288 22mm 0.8661 21.9989 7/8 0.8750 22.2250 22.5mm 0.8858 22.4993 57/64 0.8906 22.6212 23mm 0.9055 22.9997 29/32 0.9062 23.0175 59/64 0.9219 23.4163 23.5mm 0.9252 23.5001 15/16 0.9375 23.8125 24mm 0.9449 24.0005 61/64 0.9531 24.2087 24.5mm 0.9646 24.5008 31/32 0.9688 24.6075 25mm 0.9843 25.0012 63/64 0.9844 25.0038 1 1.0000 25.4000