Drill size chart: number #1–#80, letter A–Z, fractional 1/64–1 in and metric drills in decimal inches and mm (ASME B94.11M) — dimension sheet Source: Xem Studio, https://xemstudio.com/objects/drill-size-index-number-letter-fraction/ (sheet CC BY 4.0) Basis: Starrett's decimal-equivalent bulletin for the number, letter and fractional drills (printed in inches), with spot checks against three other charts; mm columns are computed here (inches × 25.4); numbers only Catalog version: 2026-10-20 Sizes: see table below - Drill sizes come in four series. Number drills #1 to #80 (#1 = 0.2280 in is the largest, #80 = 0.0135 in the smallest; CNCCookbook notes ASME B94.11M numbers run to #97 but sizes past #80 are seldom seen), letter drills A to Z (A = 0.2340 in to Z = 0.4130 in), fractional drills from 1/64 in in 1/64 in steps, and metric drills. The decimal inch values for the number, letter and fractional drills are the Starrett table as printed; the mm column is that inch value × 25.4 rounded to 0.001 mm (the fractional mm are the exact fraction × 25.4). The metric rows are the standard mm sizes with the inch value computed as mm ÷ 25.4. - Cross-checks: Newman Tools lists #1 = 0.2280, #40 = 0.0980, #80 = 0.0135, A = 0.234, E = 0.250, Z = 0.413; Xometry lists #8 = 0.199, A = 0.234 and 3.20 mm = 0.126 in; AIMS Industrial lists #80 = 0.343 mm, #1 = 5.791 mm, A = 5.944 mm and Z = 10.490 mm. All agree with the table here. The metric block is a short list of whole and half millimetres for convenience, not every metric drill size. - Use: a drill is the size of the hole it cuts only approximately. Real holes run a little over; the clearance and tap-drill tables on thread-reference-tap-drills-clearance give the drill chosen for a thread or a screw. This page is the size lookup, not a hole-fit recommendation. Not here: drill point angle, flute length series (jobber, stub, screw-machine), taps, reamers and fractional drills above 1 in. - No files: a drill is not a mating geometry on its own and a plate of holes at drill sizes would be a stand-in. The hole-size gauges for specific fasteners (rivet nuts, cable glands, PEM nuts) are on their own pages. series size decimal (in) mm (computed) number #1 0.2280 5.791 number #2 0.2210 5.613 number #3 0.2130 5.410 number #4 0.2090 5.309 number #5 0.2055 5.220 number #6 0.2040 5.182 number #7 0.2010 5.105 number #8 0.1990 5.055 number #9 0.1960 4.978 number #10 0.1935 4.915 number #11 0.1910 4.851 number #12 0.1890 4.801 number #13 0.1850 4.699 number #14 0.1820 4.623 number #15 0.1800 4.572 number #16 0.1770 4.496 number #17 0.1730 4.394 number #18 0.1695 4.305 number #19 0.1660 4.216 number #20 0.1610 4.089 number #21 0.1590 4.039 number #22 0.1570 3.988 number #23 0.1540 3.912 number #24 0.1520 3.861 number #25 0.1495 3.797 number #26 0.1470 3.734 number #27 0.1440 3.658 number #28 0.1405 3.569 number #29 0.1360 3.454 number #30 0.1285 3.264 number #31 0.1200 3.048 number #32 0.1160 2.946 number #33 0.1130 2.870 number #34 0.1110 2.819 number #35 0.1100 2.794 number #36 0.1065 2.705 number #37 0.1040 2.642 number #38 0.1015 2.578 number #39 0.0995 2.527 number #40 0.0980 2.489 number #41 0.0960 2.438 number #42 0.0935 2.375 number #43 0.0890 2.261 number #44 0.0860 2.184 number #45 0.0820 2.083 number #46 0.0810 2.057 number #47 0.0785 1.994 number #48 0.0760 1.930 number #49 0.0730 1.854 number #50 0.0700 1.778 number #51 0.0670 1.702 number #52 0.0635 1.613 number #53 0.0595 1.511 number #54 0.0550 1.397 number #55 0.0520 1.321 number #56 0.0465 1.181 number #57 0.0430 1.092 number #58 0.0420 1.067 number #59 0.0410 1.041 number #60 0.0400 1.016 number #61 0.0390 0.991 number #62 0.0380 0.965 number #63 0.0370 0.940 number #64 0.0360 0.914 number #65 0.0350 0.889 number #66 0.0330 0.838 number #67 0.0320 0.813 number #68 0.0310 0.787 number #69 0.0292 0.742 number #70 0.0280 0.711 number #71 0.0260 0.660 number #72 0.0250 0.635 number #73 0.0240 0.610 number #74 0.0225 0.571 number #75 0.0210 0.533 number #76 0.0200 0.508 number #77 0.0180 0.457 number #78 0.0160 0.406 number #79 0.0145 0.368 number #80 0.0135 0.343 letter A 0.2340 5.944 letter B 0.2380 6.045 letter C 0.2420 6.147 letter D 0.2460 6.248 letter E 0.2500 6.350 letter F 0.2570 6.528 letter G 0.2610 6.629 letter H 0.2660 6.756 letter I 0.2720 6.909 letter J 0.2770 7.036 letter K 0.2810 7.137 letter L 0.2900 7.366 letter M 0.2950 7.493 letter N 0.3020 7.671 letter O 0.3160 8.026 letter P 0.3230 8.204 letter Q 0.3320 8.433 letter R 0.3390 8.611 letter S 0.3480 8.839 letter T 0.3580 9.093 letter U 0.3680 9.347 letter V 0.3770 9.576 letter W 0.3860 9.804 letter X 0.3970 10.084 letter Y 0.4040 10.262 letter Z 0.4130 10.490 fractional 1/64 in 0.0156 0.397 fractional 1/32 in 0.0312 0.794 fractional 3/64 in 0.0469 1.191 fractional 1/16 in 0.0625 1.587 fractional 5/64 in 0.0781 1.984 fractional 3/32 in 0.0938 2.381 fractional 7/64 in 0.1094 2.778 fractional 1/8 in 0.1250 3.175 fractional 9/64 in 0.1406 3.572 fractional 5/32 in 0.1562 3.969 fractional 11/64 in 0.1719 4.366 fractional 3/16 in 0.1875 4.762 fractional 13/64 in 0.2031 5.159 fractional 7/32 in 0.2188 5.556 fractional 15/64 in 0.2344 5.953 fractional 1/4 in 0.2500 6.350 fractional 17/64 in 0.2656 6.747 fractional 9/32 in 0.2812 7.144 fractional 19/64 in 0.2969 7.541 fractional 5/16 in 0.3125 7.938 fractional 21/64 in 0.3281 8.334 fractional 11/32 in 0.3438 8.731 fractional 23/64 in 0.3594 9.128 fractional 3/8 in 0.3750 9.525 fractional 25/64 in 0.3906 9.922 fractional 13/32 in 0.4062 10.319 fractional 27/64 in 0.4219 10.716 fractional 7/16 in 0.4375 11.112 fractional 29/64 in 0.4531 11.509 fractional 15/32 in 0.4688 11.906 fractional 31/64 in 0.4844 12.303 fractional 1/2 in 0.5000 12.700 fractional 33/64 in 0.5156 13.097 fractional 17/32 in 0.5312 13.494 fractional 35/64 in 0.5469 13.891 fractional 9/16 in 0.5625 14.287 fractional 37/64 in 0.5781 14.684 fractional 19/32 in 0.5938 15.081 fractional 39/64 in 0.6094 15.478 fractional 5/8 in 0.6250 15.875 fractional 41/64 in 0.6406 16.272 fractional 21/32 in 0.6562 16.669 fractional 43/64 in 0.6719 17.066 fractional 11/16 in 0.6875 17.462 fractional 45/64 in 0.7031 17.859 fractional 23/32 in 0.7188 18.256 fractional 47/64 in 0.7344 18.653 fractional 3/4 in 0.7500 19.050 fractional 49/64 in 0.7656 19.447 fractional 25/32 in 0.7812 19.844 fractional 51/64 in 0.7969 20.241 fractional 13/16 in 0.8125 20.637 fractional 53/64 in 0.8281 21.034 fractional 27/32 in 0.8438 21.431 fractional 55/64 in 0.8594 21.828 fractional 7/8 in 0.8750 22.225 fractional 57/64 in 0.8906 22.622 fractional 29/32 in 0.9062 23.019 fractional 59/64 in 0.9219 23.416 fractional 15/16 in 0.9375 23.812 fractional 61/64 in 0.9531 24.209 fractional 31/32 in 0.9688 24.606 fractional 63/64 in 0.9844 25.003 fractional 1 in 1.0000 25.400 metric 0.5 mm 0.0197 0.5 metric 1 mm 0.0394 1 metric 1.5 mm 0.0591 1.5 metric 2 mm 0.0787 2 metric 2.5 mm 0.0984 2.5 metric 3 mm 0.1181 3 metric 3.5 mm 0.1378 3.5 metric 4 mm 0.1575 4 metric 4.5 mm 0.1772 4.5 metric 5 mm 0.1969 5 metric 5.5 mm 0.2165 5.5 metric 6 mm 0.2362 6 metric 6.5 mm 0.2559 6.5 metric 7 mm 0.2756 7 metric 7.5 mm 0.2953 7.5 metric 8 mm 0.3150 8 metric 8.5 mm 0.3346 8.5 metric 9 mm 0.3543 9 metric 9.5 mm 0.3740 9.5 metric 10 mm 0.3937 10 metric 10.5 mm 0.4134 10.5 metric 11 mm 0.4331 11 metric 11.5 mm 0.4528 11.5 metric 12 mm 0.4724 12 metric 12.5 mm 0.4921 12.5 metric 13 mm 0.5118 13 metric 14 mm 0.5512 14 metric 15 mm 0.5906 15 metric 16 mm 0.6299 16 metric 17 mm 0.6693 17 metric 18 mm 0.7087 18 metric 19 mm 0.7480 19 metric 20 mm 0.7874 20 metric 22 mm 0.8661 22 metric 25 mm 0.9843 25 Files elsewhere (not hosted by Xem Studio; license as stated by the publisher): - Starrett (bulletin hosted by FIU): Decimal and tap chart: number drills 80-1, letter drills A-Z, fractional drills 1/64 to 1-1/2 in, metric tap drills — web — Publisher's page; dimensions are facts — https://web.eng.fiu.edu/zicarell/EIN3390L%20DATA/Technical%20Info/Decimal%20and%20Tap%20chart_Starrett.pdf - Newman Tools: Decimal equivalents: fractional, number, letter and metric drill sizes (spot-check of #1, #40, #80, A, E, Z) — web — Publisher's page; dimensions are facts — https://newmantools.com/decinch.htm - Xometry: Standard drill sizes chart (spot-check of #8, A, 1/8, 5/16, 3.20 mm) — web — Publisher's page; dimensions are facts — https://community.xometry.com/kb/articles/723-standard-drill-sizes - AIMS Industrial: Drill bit metric / imperial size chart (spot-check of #80 0.343 mm, #1 5.791 mm, A 5.944 mm, Z 10.490 mm) — web — Publisher's page; dimensions are facts — https://aimsindustrial.com.au/blogs/product-guides/blog-drill-bit-metric-imperial-size-chart - CNCCookbook: Drill chart bit sizes: number, letter, fractional and metric series, ASME B94.11M number range — web — Publisher's page; dimensions are facts — https://www.cnccookbook.com/drill-chart-bit-sizes-decimal-number-letter-metric No true-size file yet: the published figures do not fix the whole shape; a measured scan is planned. API: https://xemstudio.com/api/geometry?object=drill-size-index-number-letter-fraction