Decimal Equiv alents of 8ths, 16ths, 32nds and 64ths Decimal Equiv alents of Letter Size Drills 8ths 1/8 = .125 1/4 = .250 3/8 = .375 1/2 = .500 5/8 = .625 3/4 = .750 7/8 = .875 16ths 1/16 = .0625 3/16 = .1875 5/16 = .3125 7/16 = .4375 9/16 = .5625 11/16 = .6875 13/16 = .8125 15/16 = .9375 32nds 1/32 = .03125 3/32 = .09375 5/32 = .15625 7/32 = .21875 9/32 = .28125 11/32 = .34375 13/32 = .40625 15/32 = .46875 17/32 = .53125 19/32 = .5975 21/32 = .65625 23/32 = .71875 25/32 = .78125 27/32 = .84375 29/32 = .90625 31/32 = .96875 64ths 1/64 = .015625 3/64 = .046875 5/64 = .078125 7/64 = .109375 9/64 = .140625 11/64 = .171875 13/64 = .203125 15/64 = .234375 17/64 = .265625 19/64 = .296875 21/64 = .328125 23/64 = .359375 25/64 = .390625 27/64 = .421875 29/64 = .453125 31/64 = .484375 33/64 = .515625 35/64 = .546875 Letter Size of Drill in Inches A .234 B .238 C .242 D .246 E .250 F .257 G .261 H .266 I .272 J .277 64ths 37/64 = .578125 39/64 = .609375 41/64 = .640625 43/64 = .671875 45/64 = .703125 47/64 = .734375 49/64 = .765625 51/64 = .796875 53/64 = .828125 55/64 = .859375 57/64 = .890625 59/64 = .921875 61/64 = .953125 63/64 = .984375 Decimal Equiv alents of Number Size Drills No. Size of Drill in Inches 1 .2280 2 .2210 3 .2130 4 .2090 5 .2055 6 .2040 7 .2010 8 .1990 9 .1960 10 .1935 11 .1910 12 .1890 13 .1850 14 .1820 No. Size of Drill in Inches 15 .1800 16 .1770 17 .1730 18 .1695 19 .1660 20 .1610 21 .1590 22 .1570 23 .1540 24 .1520 25 .1495 26 .1470 27 .1440 28 .1405 No. Size of Drill in Inches 29 .1360 30 .1285 31 .1200 32 .1160 33 .1130 34 .1110 35 .1100 36 .1065 37 .1040 38 .1015 39 .0995 40 .0980 41 .0960 42 .0935 Letter Size of Drill in Inches K .281 L .290 M .295 N .302 O .316 P .323 Q .332 R .339 S .348 Letter Size of Drill in Inches T .358 U .368 V .377 W .386 X .397 Y .404 Z .413 No. Size of Drill in Inches 43 .0890 44 .0860 45 .0820 46 .0810 47 .0785 48 .0760 49 .0730 50 .0700 51 .0670 52 .0635 53 .0595 54 .0550 55 .0520 56 .0465 No. Size of Drill in Inches 57 .0430 58 .0420 59 .0410 60 .0400 61 .0390 62 .0380 63 .0370 64 .0360 65 .0350 66 .0330 67 .0320 68 .0310 No. Size of Drill in Inches 69 .0292 70 .0280 71 .0260 72 .0250 73 .0240 74 .0225 75 .0210 76 .0200 77 .0180 78 .0160 79 .0145 80 .0135 American St andard Pipe Thread and Tap Drill Sizes Pipe Size (in) Threads Per Inch Root Diameter Small End of Pipe and Gage Tap Drill Straight NPS Taper NPT 1/8 27 .3339" Q 11/32" 1/4 18 .4329" 7/16" 7/16" 3/8 .5676" 9/16" 37/64" 1/2 14 .7013" 45/64" 23/32" 3/4 .9105" 29/32" 59/64" 1 11-1/2 1.1441" 1-9/64" 1-5/32" 1-1/4 1.4876" 1-31/64" 1-1/2" 1-1/2 1.7265" 1-47/64" 1-3/4" 2 2.1995" 2-13/64" 2-7/32" 581 starrett.com R eference T ables