Drill Bit Size Chart
Tools
Data 2026.07.13-audit.1
Checking connection

Nominal diameter reference

Four naming systems.
One measured axis.

Number and letter drills fill gaps that coarse fractions leave behind; metric sizes follow a different cadence. Filter all four without hiding where each value came from.

Combined nominal drill-size reference — 296 entries
Size System Inches Millimetres
#80 number 0.0135 0.343
#79 number 0.0145 0.368
1/64 fractional 0.0156 0.397
#78 number 0.0160 0.406
#77 number 0.0180 0.457
0.5 mm metric 0.0197 0.500
#76 number 0.0200 0.508
#75 number 0.0210 0.533
#74 number 0.0225 0.571
0.6 mm metric 0.0236 0.600
#73 number 0.0240 0.610
#72 number 0.0250 0.635
#71 number 0.0260 0.660
0.7 mm metric 0.0276 0.700
#70 number 0.0280 0.711
#69 number 0.0292 0.742
#68 number 0.0310 0.787
1/32 fractional 0.0313 0.794
0.8 mm metric 0.0315 0.800
#67 number 0.0320 0.813
#66 number 0.0330 0.838
#65 number 0.0350 0.889
0.9 mm metric 0.0354 0.900
#64 number 0.0360 0.914
#63 number 0.0370 0.940
#62 number 0.0380 0.965
#61 number 0.0390 0.991
1 mm metric 0.0394 1.000
#60 number 0.0400 1.016
#59 number 0.0410 1.041
#58 number 0.0420 1.067
#57 number 0.0430 1.092
1.1 mm metric 0.0433 1.100
#56 number 0.0465 1.181
3/64 fractional 0.0469 1.191
1.2 mm metric 0.0472 1.200
1.3 mm metric 0.0512 1.300
#55 number 0.0520 1.321
#54 number 0.0550 1.397
1.4 mm metric 0.0551 1.400
1.5 mm metric 0.0591 1.500
#53 number 0.0595 1.511
1/16 fractional 0.0625 1.587
1.6 mm metric 0.0630 1.600
#52 number 0.0635 1.613
1.7 mm metric 0.0669 1.700
#51 number 0.0670 1.702
#50 number 0.0700 1.778
1.8 mm metric 0.0709 1.800
#49 number 0.0730 1.854
1.9 mm metric 0.0748 1.900
#48 number 0.0760 1.930
5/64 fractional 0.0781 1.984
#47 number 0.0785 1.994
2 mm metric 0.0787 2.000
#46 number 0.0810 2.057
#45 number 0.0820 2.083
2.1 mm metric 0.0827 2.100
#44 number 0.0860 2.184
2.2 mm metric 0.0866 2.200
#43 number 0.0890 2.261
2.3 mm metric 0.0906 2.300
#42 number 0.0935 2.375
3/32 fractional 0.0938 2.381
2.4 mm metric 0.0945 2.400
#41 number 0.0960 2.438
#40 number 0.0980 2.489
2.5 mm metric 0.0984 2.500
#39 number 0.0995 2.527
#38 number 0.1015 2.578
2.6 mm metric 0.1024 2.600
#37 number 0.1040 2.642
2.7 mm metric 0.1063 2.700
#36 number 0.1065 2.705
7/64 fractional 0.1094 2.778
#35 number 0.1100 2.794
2.8 mm metric 0.1102 2.800
#34 number 0.1110 2.819
#33 number 0.1130 2.870
2.9 mm metric 0.1142 2.900
#32 number 0.1160 2.946
3 mm metric 0.1181 3.000
#31 number 0.1200 3.048
3.1 mm metric 0.1220 3.100
1/8 fractional 0.1250 3.175
3.2 mm metric 0.1260 3.200
#30 number 0.1285 3.264
3.3 mm metric 0.1299 3.300
3.4 mm metric 0.1339 3.400
#29 number 0.1360 3.454
3.5 mm metric 0.1378 3.500
#28 number 0.1405 3.569
9/64 fractional 0.1406 3.572
3.6 mm metric 0.1417 3.600
#27 number 0.1440 3.658
3.7 mm metric 0.1457 3.700
#26 number 0.1470 3.734
#25 number 0.1495 3.797
3.8 mm metric 0.1496 3.800
#24 number 0.1520 3.861
3.9 mm metric 0.1535 3.900
#23 number 0.1540 3.912
5/32 fractional 0.1563 3.969
#22 number 0.1570 3.988
4 mm metric 0.1575 4.000
#21 number 0.1590 4.039
#20 number 0.1610 4.089
4.1 mm metric 0.1614 4.100
4.2 mm metric 0.1654 4.200
#19 number 0.1660 4.216
4.3 mm metric 0.1693 4.300
#18 number 0.1695 4.305
11/64 fractional 0.1719 4.366
#17 number 0.1730 4.394
4.4 mm metric 0.1732 4.400
#16 number 0.1770 4.496
4.5 mm metric 0.1772 4.500
#15 number 0.1800 4.572
4.6 mm metric 0.1811 4.600
#14 number 0.1820 4.623
#13 number 0.1850 4.699
4.7 mm metric 0.1850 4.700
3/16 fractional 0.1875 4.762
4.8 mm metric 0.1890 4.800
#12 number 0.1890 4.801
#11 number 0.1910 4.851
4.9 mm metric 0.1929 4.900
#10 number 0.1935 4.915
#9 number 0.1960 4.978
5 mm metric 0.1969 5.000
#8 number 0.1990 5.055
5.1 mm metric 0.2008 5.100
#7 number 0.2010 5.105
13/64 fractional 0.2031 5.159
#6 number 0.2040 5.182
5.2 mm metric 0.2047 5.200
#5 number 0.2055 5.220
5.3 mm metric 0.2087 5.300
#4 number 0.2090 5.309
5.4 mm metric 0.2126 5.400
#3 number 0.2130 5.410
5.5 mm metric 0.2165 5.500
7/32 fractional 0.2188 5.556
5.6 mm metric 0.2205 5.600
#2 number 0.2210 5.613
5.7 mm metric 0.2244 5.700
#1 number 0.2280 5.791
5.8 mm metric 0.2283 5.800
5.9 mm metric 0.2323 5.900
A letter 0.2340 5.944
15/64 fractional 0.2344 5.953
6 mm metric 0.2362 6.000
B letter 0.2380 6.045
6.1 mm metric 0.2402 6.100
C letter 0.2420 6.147
6.2 mm metric 0.2441 6.200
D letter 0.2460 6.248
6.3 mm metric 0.2480 6.300
E letter 0.2500 6.350
1/4 fractional 0.2500 6.350
6.4 mm metric 0.2520 6.400
6.5 mm metric 0.2559 6.500
F letter 0.2570 6.528
6.6 mm metric 0.2598 6.600
G letter 0.2610 6.629
6.7 mm metric 0.2638 6.700
17/64 fractional 0.2656 6.747
H letter 0.2660 6.756
6.8 mm metric 0.2677 6.800
6.9 mm metric 0.2717 6.900
I letter 0.2720 6.909
7 mm metric 0.2756 7.000
J letter 0.2770 7.036
7.1 mm metric 0.2795 7.100
K letter 0.2810 7.137
9/32 fractional 0.2813 7.144
7.2 mm metric 0.2835 7.200
7.3 mm metric 0.2874 7.300
L letter 0.2900 7.366
7.4 mm metric 0.2913 7.400
M letter 0.2950 7.493
7.5 mm metric 0.2953 7.500
19/64 fractional 0.2969 7.541
7.6 mm metric 0.2992 7.600
N letter 0.3020 7.671
7.7 mm metric 0.3031 7.700
7.8 mm metric 0.3071 7.800
7.9 mm metric 0.3110 7.900
5/16 fractional 0.3125 7.938
8 mm metric 0.3150 8.000
O letter 0.3160 8.026
8.1 mm metric 0.3189 8.100
8.2 mm metric 0.3228 8.200
P letter 0.3230 8.204
8.3 mm metric 0.3268 8.300
21/64 fractional 0.3281 8.334
8.4 mm metric 0.3307 8.400
Q letter 0.3320 8.433
8.5 mm metric 0.3346 8.500
8.6 mm metric 0.3386 8.600
R letter 0.3390 8.611
8.7 mm metric 0.3425 8.700
11/32 fractional 0.3438 8.731
8.8 mm metric 0.3465 8.800
S letter 0.3480 8.839
8.9 mm metric 0.3504 8.900
9 mm metric 0.3543 9.000
T letter 0.3580 9.093
9.1 mm metric 0.3583 9.100
23/64 fractional 0.3594 9.128
9.2 mm metric 0.3622 9.200
9.3 mm metric 0.3661 9.300
U letter 0.3680 9.347
9.4 mm metric 0.3701 9.400
9.5 mm metric 0.3740 9.500
3/8 fractional 0.3750 9.525
V letter 0.3770 9.576
9.6 mm metric 0.3780 9.600
9.7 mm metric 0.3819 9.700
9.8 mm metric 0.3858 9.800
W letter 0.3860 9.804
9.9 mm metric 0.3898 9.900
25/64 fractional 0.3906 9.922
10 mm metric 0.3937 10.000
X letter 0.3970 10.084
10.1 mm metric 0.3976 10.100
10.2 mm metric 0.4016 10.200
Y letter 0.4040 10.262
10.3 mm metric 0.4055 10.300
13/32 fractional 0.4063 10.319
10.4 mm metric 0.4094 10.400
Z letter 0.4130 10.490
10.5 mm metric 0.4134 10.500
10.6 mm metric 0.4173 10.600
10.7 mm metric 0.4213 10.700
27/64 fractional 0.4219 10.716
10.8 mm metric 0.4252 10.800
10.9 mm metric 0.4291 10.900
11 mm metric 0.4331 11.000
11.1 mm metric 0.4370 11.100
7/16 fractional 0.4375 11.112
11.2 mm metric 0.4409 11.200
11.3 mm metric 0.4449 11.300
11.4 mm metric 0.4488 11.400
11.5 mm metric 0.4528 11.500
29/64 fractional 0.4531 11.509
11.6 mm metric 0.4567 11.600
11.7 mm metric 0.4606 11.700
11.8 mm metric 0.4646 11.800
11.9 mm metric 0.4685 11.900
15/32 fractional 0.4688 11.906
12 mm metric 0.4724 12.000
12.1 mm metric 0.4764 12.100
12.2 mm metric 0.4803 12.200
12.3 mm metric 0.4843 12.300
31/64 fractional 0.4844 12.303
12.4 mm metric 0.4882 12.400
12.5 mm metric 0.4921 12.500
12.6 mm metric 0.4961 12.600
1/2 fractional 0.5000 12.700
12.7 mm metric 0.5000 12.700
12.8 mm metric 0.5039 12.800
12.9 mm metric 0.5079 12.900
13 mm metric 0.5118 13.000
33/64 fractional 0.5156 13.097
17/32 fractional 0.5313 13.494
35/64 fractional 0.5469 13.891
9/16 fractional 0.5625 14.287
37/64 fractional 0.5781 14.684
19/32 fractional 0.5938 15.081
39/64 fractional 0.6094 15.478
5/8 fractional 0.6250 15.875
41/64 fractional 0.6406 16.272
21/32 fractional 0.6563 16.669
43/64 fractional 0.6719 17.066
11/16 fractional 0.6875 17.462
45/64 fractional 0.7031 17.859
23/32 fractional 0.7188 18.256
47/64 fractional 0.7344 18.653
3/4 fractional 0.7500 19.050
49/64 fractional 0.7656 19.447
25/32 fractional 0.7813 19.844
51/64 fractional 0.7969 20.241
13/16 fractional 0.8125 20.637
53/64 fractional 0.8281 21.034
27/32 fractional 0.8438 21.431
55/64 fractional 0.8594 21.828
7/8 fractional 0.8750 22.225
57/64 fractional 0.8906 22.622
29/32 fractional 0.9063 23.019
59/64 fractional 0.9219 23.416
15/16 fractional 0.9375 23.813
61/64 fractional 0.9531 24.209
31/32 fractional 0.9688 24.606
63/64 fractional 0.9844 25.003
1 fractional 1.0000 25.400

Showing 296 sizes.

How to read the four series

Why one bit has four names.

Each series was drawn up for a different job, and they overlap on the same diameter axis. The ranges below are read straight from the table above.

Number drills 80 ROWS

#1 → #80 0.0135 in – 0.2280 in

The number runs backwards: #1 is the largest at 0.2280 in, and #80 is the smallest at 0.0135 in. A higher number means a smaller hole—the single most common misread of this chart. Most cutting-tap drills for small threads live in this series.

Letter drills 26 ROWS

A → Z 0.2340 in – 0.4130 in

Letters ascend with diameter, and the series starts just above the largest number drill (A is 0.2340 in against #1 at 0.2280 in). It carries the sequence through the range where fractions alone are too coarse for a tapped or reamed hole.

Fractional-inch drills 64 ROWS · 1/64 STEPS

1/64 → 1 0.0156 in – 1.0000 in

The only series whose designation is its diameter: 1/4 in is exactly 0.2500 in (6.350 mm) by definition, not by measurement. Every millimetre value shown for a fraction on this site is a conversion of that exact number.

Metric comparison series 126 ROWS · 0.1 MM STEPS

0.5 mm → 13 mm 0.0197 in – 0.5118 in

A generated 0.1 mm ladder for comparison, not the contents of any commercial set. It exists so a metric target can be placed against the inch series; what your supplier actually stocks is a separate question.

The four series never align exactly. Where a metric size looks equal to a fraction it usually is not—compare the signed difference before treating one as the other.