Drill Bit Naming Chart

In order to allow for precision, drill bits come in an extremely wide range of sizes. The sizes use several different naming
conventions, including fractions, numbers and letters. All fractions of 64ths, from 1/64th through 63/64ths, are named
by their lowest fractional equivalent (1/32”, 1/16”, 5/64”, etc...). There are also size options that fall between many of
these fractions. Common # sizes go from #80 through #1, in ascending sizes, up to .2280. Sizes over .2280 which aren’t
named for their fraction of 64ths, are named by letters, ascending from A (.2340) through Z (.4130). The chart below
shows drill sizes up to 1 inch in diameter.

Drill Bit # Hole Size Drill Bit # Hole Size Drill Bit # Hole Size Drill Bit # Hole Size
80 = 0.0135 43 = 0.0890 8 = 0.1990 25/64” = 0.3906
79 = 0.0145 42 = 0.0935 7 = 0.2010 X = 0.3970
1/64” = 0.0156 3/32” = 0.0938 13/64” = 0.2031 Y = 0.4040
78 = 0.0160 41 = 0.0960 6 = 0.2040 13/32” = 0.4063
77 = 0.0180 40 = 0.0980 5 = 0.2055 Z = 0.4130
76 = 0.0200 39 = 0.0995 4 = 0.2090 27/64” = 0.4219
75 = 0.0210 38 = 0.1015 3 = 0.2130 7/16” = 0.4375
74 = 0.0225 37 = 0.1040 7/32” = 0.2188 29/64” = 0.4531
73 = 0.0240 36 = 0.1065 2 = 0.2210 15/32” = 0.4688
72 = 0.0250 7/64” = 0.1094 1 = 0.2280 31/64” = 0.4844
71 = 0.0260 35 = 0.1100 A = 0.2340 1/2 = 0.5000
70 = 0.0280 34 = 0.1110 15/64” = 0.2344 33/64” = 0.5156
69 = 0.0292 33 = 0.1130 B = 0.2380 17/32” = 0.5313
68 = 0.0310 32 = 0.1160 C = 0.2420 35/64” = 0.5469
1/32” = 0.0313 31 = 0.1200 D = 0.2460 9/16” = 0.5625
67 = 0.0320 1/8” = 0.1250 1/4” or (E) = 0.2500 37/64” = 0.5781
66 = 0.0330 30 = 0.1285 F = 0.2570 19/32” = 0.5938
65 = 0.0350 29 = 0.1360 G = 0.2610 39/64” = 0.6094
64 = 0.0360 28 = 0.1405 17/64” = 0.2656 5/8” = 0.6250
63 = 0.0370 9/64” = 0.1406 H = 0.2660 41/64” = 0.6406
62 = 0.0380 27 = 0.1440 I = 0.2720 21/32” = 0.6563
61 = 0.0390 26 = 0.1470 J = 0.2770 43/64” = 0.6719
60 = 0.0400 25 = 0.1495 K = 0.2810 11/16” = 0.6875
59 = 0.0410 24 = 0.1520 9/32” = 0.2813 45/64” = 0.7031
58 = 0.0420 23 = 0.1540 L = 0.2900 23/32” = 0.7188
57 = 0.0430 5/32” = 0.1563 M = 0.2950 47/64” = 0.7344
56 = 0.0465 22 = 0.1570 19/64” = 0.2969 3/4” = 0.7500
3/64” = 0.0469 21 = 0.1590 N = 0.3020 49/64” = 0.7656
55 = 0.0520 20 = 0.1610 5/16” = 0.3125 25/32” = 0.7813
54 = 0.0550 19 = 0.1660 O = 0.3160 51/64” = 0.7969
53 = 0.0595 18 = 0.1695 P = 0.3230 13/16” = 0.8125
1/16” = 0.0625 11/64” = 0.1719 21/64” = 0.3281 53/64” = 0.8281
52 = 0.0635 17 = 0.1730 Q = 0.3320 27/32” = 0.8438
51 = 0.0670 16 = 0.1770 R = 0.3390 55/64” = 0.8594
50 = 0.0700 15 = 0.1800 11/32” = 0.3438 7/8” = 0.8750
49 = 0.0730 14 = 0.1820 S = 0.3480 57/64” = 0.8906
48 = 0.0760 13 = 0.1850 T = 0.3580 29/32” = 0.9063
5/64” = 0.0781 3/16” = 0.1875 23/64” = 0.3594 59/64” = 0.9219
47 = 0.0785 12 = 0.1890 U = 0.3680 15/16” = 0.9375
46 = 0.0810 11 = 0.1910 3/8” = 0.3750 61/64” = 0.9531
45 = 0.0820 10 = 0.1935 V = 0.3770 31/32” = 0.9688
44 = 0.0860 9 = 0.1960 W = 0.3860 63/64” = 0.9844

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