Drilling

Drill Bit Size Chart

Fractional, number, letter and metric bits interleaved by actual diameter — the way they sit in a drill index, not split into four separate tables you have to cross-check.

The four systems overlap heavily. 1/4″, E and 6.35 mm are the same hole. A #7 (0.2010″) and a 5.1 mm (0.2008″) differ by two ten-thousandths — interchangeable for clearance, not for a reamed fit.

Fractional, number, letter and metric drill bit sizes sorted by diameter, with interchangeable sizes
			Interchangeable with
#80	Number	0.0135	#79
#79	Number	0.0145	#80, 1/64", #78
1/64"	Fractional	0.0156	#79, #78
#78	Number	0.0160	1/64", #79, #77
#77	Number	0.0180	#78, 0.5 mm
0.5 mm	Metric	0.0197	#77, #76, #75
#76	Number	0.0200	0.5 mm, #75
#75	Number	0.0210	#76, 0.5 mm, #74
#74	Number	0.0225	#75, 0.6 mm, #73
0.6 mm	Metric	0.0236	#74, #73, #72
#73	Number	0.0240	0.6 mm, #74, #72, #71
#72	Number	0.0250	#73, 0.6 mm, #71
#71	Number	0.0260	#72, #73, 0.7 mm
0.7 mm	Metric	0.0276	#71, #70, #69
#70	Number	0.0280	0.7 mm, #69
#69	Number	0.0292	#70, 0.7 mm, #68
#68	Number	0.0310	#69, 1/32", 0.8 mm, #67
1/32"	Fractional	0.0312	#68, 0.8 mm, #67, #66
0.8 mm	Metric	0.0315	1/32", #68, #67, #66
#67	Number	0.0320	0.8 mm, 1/32", #68, #66
#66	Number	0.0330	#67, 0.8 mm, 1/32"
#65	Number	0.0350	0.9 mm, #64, #63
0.9 mm	Metric	0.0354	#65, #64, #63
#64	Number	0.0360	0.9 mm, #65, #63
#63	Number	0.0370	#64, 0.9 mm, #65, #62
#62	Number	0.0380	#63, #61, 1.0 mm
#61	Number	0.0390	#62, 1.0 mm, #60
1.0 mm	Metric	0.0394	#61, #62, #60, #59
#60	Number	0.0400	1.0 mm, #61, #59
#59	Number	0.0410	#60, 1.0 mm, #58, #57
#58	Number	0.0420	#59, #57, 1.1 mm
#57	Number	0.0430	#58, #59, 1.1 mm
1.1 mm	Metric	0.0433	#57, #58
#56	Number	0.0465	3/64", 1.2 mm
3/64"	Fractional	0.0469	#56, 1.2 mm
1.2 mm	Metric	0.0472	3/64", #56
1.3 mm	Metric	0.0512	#55
#55	Number	0.0520	1.3 mm
#54	Number	0.0550	1.4 mm
1.4 mm	Metric	0.0551	#54
1.5 mm	Metric	0.0591	#53
#53	Number	0.0595	1.5 mm
1/16"	Fractional	0.0625	1.6 mm, #52
1.6 mm	Metric	0.0630	1/16", #52
#52	Number	0.0635	1.6 mm, 1/16"
1.7 mm	Metric	0.0669	#51
#51	Number	0.0670	1.7 mm
#50	Number	0.0700	1.8 mm
1.8 mm	Metric	0.0709	#50
#49	Number	0.0730	1.9 mm
1.9 mm	Metric	0.0748	#49, #48
#48	Number	0.0760	1.9 mm
5/64"	Fractional	0.0781	#47, 2.0 mm
#47	Number	0.0785	5/64", 2.0 mm
2.0 mm	Metric	0.0787	#47, 5/64"
#46	Number	0.0810	#45, 2.1 mm
#45	Number	0.0820	#46, 2.1 mm
2.1 mm	Metric	0.0827	#45, #46
#44	Number	0.0860	2.2 mm
2.2 mm	Metric	0.0866	#44
#43	Number	0.0890	2.3 mm
2.3 mm	Metric	0.0906	#43
#42	Number	0.0935	3/32", 2.4 mm
3/32"	Fractional	0.0938	#42, 2.4 mm
2.4 mm	Metric	0.0945	3/32", #42, #41
#41	Number	0.0960	2.4 mm
#40	Number	0.0980	2.5 mm, #39
2.5 mm	Metric	0.0984	#40, #39
#39	Number	0.0995	2.5 mm, #40
#38	Number	0.1015	2.6 mm
2.6 mm	Metric	0.1024	#38, #37
#37	Number	0.1040	2.6 mm
2.7 mm	Metric	0.1063	#36
#36	Number	0.1065	2.7 mm
7/64"	Fractional	0.1094	#35, 2.8 mm, #34
#35	Number	0.1100	7/64", 2.8 mm, #34
2.8 mm	Metric	0.1102	#35, 7/64", #34
#34	Number	0.1110	2.8 mm, #35, 7/64"
#33	Number	0.1130	2.9 mm
2.9 mm	Metric	0.1142	#33, #32
#32	Number	0.1160	2.9 mm
3.0 mm	Metric	0.1181	#31
#31	Number	0.1200	3.0 mm
3.1 mm	Metric	0.1221
1/8"	Fractional	0.1250	3.2 mm
3.2 mm	Metric	0.1260	1/8"
#30	Number	0.1285	3.3 mm
3.3 mm	Metric	0.1299	#30
3.4 mm	Metric	0.1339
#29	Number	0.1360	3.5 mm
3.5 mm	Metric	0.1378	#29
#28	Number	0.1405	9/64", 3.6 mm
9/64"	Fractional	0.1406	#28, 3.6 mm
3.6 mm	Metric	0.1417	9/64", #28
#27	Number	0.1440	3.7 mm
3.7 mm	Metric	0.1457	#27, #26
#26	Number	0.1470	3.7 mm
#25	Number	0.1495	3.8 mm
3.8 mm	Metric	0.1496	#25
#24	Number	0.1520	3.9 mm
3.9 mm	Metric	0.1535	#24, #23
#23	Number	0.1540	3.9 mm
5/32"	Fractional	0.1562	#22, 4.0 mm
#22	Number	0.1570	5/32", 4.0 mm
4.0 mm	Metric	0.1575	#22, 5/32", #21
#21	Number	0.1590	4.0 mm
#20	Number	0.1610	4.1 mm
4.1 mm	Metric	0.1614	#20
4.2 mm	Metric	0.1653	#19
#19	Number	0.1660	4.2 mm
4.3 mm	Metric	0.1693	#18
#18	Number	0.1695	4.3 mm
11/64"	Fractional	0.1719	#17, 4.4 mm
#17	Number	0.1730	11/64", 4.4 mm
4.4 mm	Metric	0.1732	#17, 11/64"
#16	Number	0.1770	4.5 mm
4.5 mm	Metric	0.1772	#16
#15	Number	0.1800	4.6 mm
4.6 mm	Metric	0.1811	#15, #14
#14	Number	0.1820	4.6 mm
#13	Number	0.1850	4.7 mm
4.7 mm	Metric	0.1850	#13
3/16"	Fractional	0.1875	4.8 mm, #12
4.8 mm	Metric	0.1890	3/16", #12
#12	Number	0.1890	4.8 mm, 3/16"
#11	Number	0.1910	4.9 mm
4.9 mm	Metric	0.1929	#11, #10
#10	Number	0.1935	4.9 mm
#9	Number	0.1960	5.0 mm
5.0 mm	Metric	0.1968	#9
#8	Number	0.1990	5.1 mm
5.1 mm	Metric	0.2008	#8, #7
#7	Number	0.2010	5.1 mm
13/64"	Fractional	0.2031	#6, 5.2 mm
#6	Number	0.2040	13/64", 5.2 mm, #5
5.2 mm	Metric	0.2047	#6, 13/64", #5
#5	Number	0.2055	5.2 mm, #6
5.3 mm	Metric	0.2087	#4
#4	Number	0.2090	5.3 mm
5.4 mm	Metric	0.2126	#3
#3	Number	0.2130	5.4 mm
5.5 mm	Metric	0.2165
7/32"	Fractional	0.2188	5.6 mm
5.6 mm	Metric	0.2205	7/32", #2
#2	Number	0.2210	5.6 mm
5.7 mm	Metric	0.2244
#1	Number	0.2280	5.8 mm
5.8 mm	Metric	0.2283	#1
5.9 mm	Metric	0.2323	A
A	Letter	0.2340	5.9 mm, 15/64"
15/64"	Fractional	0.2344	A, 6.0 mm
6.0 mm	Metric	0.2362	15/64", B
B	Letter	0.2380	6.0 mm
6.1 mm	Metric	0.2402	C
C	Letter	0.2420	6.1 mm
6.2 mm	Metric	0.2441	D
D	Letter	0.2460	6.2 mm
6.3 mm	Metric	0.2480	1/4", E
1/4"	Fractional	0.2500	6.3 mm, E, 6.4 mm
E	Letter	0.2500	1/4", 6.3 mm, 6.4 mm
6.4 mm	Metric	0.2520	E, 1/4"
6.5 mm	Metric	0.2559	F
F	Letter	0.2570	6.5 mm
6.6 mm	Metric	0.2598	G
G	Letter	0.2610	6.6 mm
6.7 mm	Metric	0.2638	17/64"
17/64"	Fractional	0.2656	6.7 mm, H
H	Letter	0.2660	17/64", 6.8 mm
6.8 mm	Metric	0.2677	H
6.9 mm	Metric	0.2717	I
I	Letter	0.2720	6.9 mm
7.0 mm	Metric	0.2756	J
J	Letter	0.2770	7.0 mm
7.1 mm	Metric	0.2795	K, 9/32"
K	Letter	0.2810	7.1 mm, 9/32"
9/32"	Fractional	0.2812	K, 7.1 mm
7.2 mm	Metric	0.2835
7.3 mm	Metric	0.2874
L	Letter	0.2900	7.4 mm
7.4 mm	Metric	0.2913	L
M	Letter	0.2950	7.5 mm, 19/64"
7.5 mm	Metric	0.2953	M, 19/64"
19/64"	Fractional	0.2969	7.5 mm, M
7.6 mm	Metric	0.2992
N	Letter	0.3020	7.7 mm
7.7 mm	Metric	0.3031	N
7.8 mm	Metric	0.3071
7.9 mm	Metric	0.3110	5/16"
5/16"	Fractional	0.3125	7.9 mm
8.0 mm	Metric	0.3150	O
O	Letter	0.3160	8.0 mm
8.1 mm	Metric	0.3189
8.2 mm	Metric	0.3228	P
P	Letter	0.3230	8.2 mm
8.3 mm	Metric	0.3268	21/64"
21/64"	Fractional	0.3281	8.3 mm
8.4 mm	Metric	0.3307	Q
Q	Letter	0.3320	8.4 mm
8.5 mm	Metric	0.3347
8.6 mm	Metric	0.3386	R
R	Letter	0.3390	8.6 mm
8.7 mm	Metric	0.3425	11/32"
11/32"	Fractional	0.3438	8.7 mm
8.8 mm	Metric	0.3465	S
S	Letter	0.3480	8.8 mm
8.9 mm	Metric	0.3504
9.0 mm	Metric	0.3543
T	Letter	0.3580	9.1 mm, 23/64"
9.1 mm	Metric	0.3583	T, 23/64"
23/64"	Fractional	0.3594	9.1 mm, T
9.2 mm	Metric	0.3622
9.3 mm	Metric	0.3661	U
U	Letter	0.3680	9.3 mm
9.4 mm	Metric	0.3701
9.5 mm	Metric	0.3740	3/8"
3/8"	Fractional	0.3750	9.5 mm
V	Letter	0.3770	9.6 mm
9.6 mm	Metric	0.3780	V
9.7 mm	Metric	0.3819
9.8 mm	Metric	0.3858	W
W	Letter	0.3860	9.8 mm
9.9 mm	Metric	0.3898	25/64"
25/64"	Fractional	0.3906	9.9 mm
10.0 mm	Metric	0.3937
X	Letter	0.3970	10.1 mm
10.1 mm	Metric	0.3976	X
10.2 mm	Metric	0.4016
Y	Letter	0.4040	10.3 mm
10.3 mm	Metric	0.4055	Y, 13/32"
13/32"	Fractional	0.4062	10.3 mm
10.4 mm	Metric	0.4094
Z	Letter	0.4130	10.5 mm
10.5 mm	Metric	0.4134	Z
10.6 mm	Metric	0.4173
10.7 mm	Metric	0.4213	27/64"
27/64"	Fractional	0.4219	10.7 mm
10.8 mm	Metric	0.4252
10.9 mm	Metric	0.4291
11.0 mm	Metric	0.4331
11.1 mm	Metric	0.4370	7/16"
7/16"	Fractional	0.4375	11.1 mm
11.2 mm	Metric	0.4409
11.3 mm	Metric	0.4449
11.4 mm	Metric	0.4488
11.5 mm	Metric	0.4528	29/64"
29/64"	Fractional	0.4531	11.5 mm
11.6 mm	Metric	0.4567
11.7 mm	Metric	0.4606
11.8 mm	Metric	0.4646
11.9 mm	Metric	0.4685	15/32"
15/32"	Fractional	0.4688	11.9 mm
12.0 mm	Metric	0.4724
12.1 mm	Metric	0.4764
12.2 mm	Metric	0.4803
12.3 mm	Metric	0.4843	31/64"
31/64"	Fractional	0.4844	12.3 mm
12.4 mm	Metric	0.4882
12.5 mm	Metric	0.4921
12.6 mm	Metric	0.4961
1/2"	Fractional	0.5000	12.7 mm
12.7 mm	Metric	0.5000	1/2"
12.8 mm	Metric	0.5039
12.9 mm	Metric	0.5079
13.0 mm	Metric	0.5118
33/64"	Fractional	0.5156
17/32"	Fractional	0.5312	13.5 mm
13.5 mm	Metric	0.5315	17/32"
35/64"	Fractional	0.5469
14.0 mm	Metric	0.5512
9/16"	Fractional	0.5625
14.5 mm	Metric	0.5709
37/64"	Fractional	0.5781
15.0 mm	Metric	0.5906
19/32"	Fractional	0.5938
39/64"	Fractional	0.6094	15.5 mm
15.5 mm	Metric	0.6102	39/64"
5/8"	Fractional	0.6250
16.0 mm	Metric	0.6299
41/64"	Fractional	0.6406
16.5 mm	Metric	0.6496
21/32"	Fractional	0.6562
17.0 mm	Metric	0.6693
43/64"	Fractional	0.6719
11/16"	Fractional	0.6875	17.5 mm
17.5 mm	Metric	0.6890	11/16"
45/64"	Fractional	0.7031
18.0 mm	Metric	0.7087
23/32"	Fractional	0.7188
18.5 mm	Metric	0.7284
47/64"	Fractional	0.7344
19.0 mm	Metric	0.7480	3/4"
3/4"	Fractional	0.7500	19.0 mm
49/64"	Fractional	0.7656
19.5 mm	Metric	0.7677
25/32"	Fractional	0.7812
20.0 mm	Metric	0.7874
51/64"	Fractional	0.7969
20.5 mm	Metric	0.8071
13/16"	Fractional	0.8125
21.0 mm	Metric	0.8268	53/64"
53/64"	Fractional	0.8281	21.0 mm
27/32"	Fractional	0.8438
21.5 mm	Metric	0.8465
55/64"	Fractional	0.8594
22.0 mm	Metric	0.8661
7/8"	Fractional	0.8750
22.5 mm	Metric	0.8858
57/64"	Fractional	0.8906
23.0 mm	Metric	0.9055	29/32"
29/32"	Fractional	0.9062	23.0 mm
59/64"	Fractional	0.9219
23.5 mm	Metric	0.9252
15/16"	Fractional	0.9375
24.0 mm	Metric	0.9449
61/64"	Fractional	0.9531
24.5 mm	Metric	0.9646
31/32"	Fractional	0.9688
25.0 mm	Metric	0.9842	63/64"
63/64"	Fractional	0.9844	25.0 mm
1"	Fractional	1.0000
1-1/32"	Fractional	1.0312
1-1/16"	Fractional	1.0625
1-3/32"	Fractional	1.0938
1-1/8"	Fractional	1.1250
1-5/32"	Fractional	1.1562
1-3/16"	Fractional	1.1875
1-7/32"	Fractional	1.2188
1-1/4"	Fractional	1.2500
1-9/32"	Fractional	1.2812
1-5/16"	Fractional	1.3125
1-11/32"	Fractional	1.3438
1-3/8"	Fractional	1.3750
1-13/32"	Fractional	1.4062
1-7/16"	Fractional	1.4375
1-15/32"	Fractional	1.4688
1-1/2"	Fractional	1.5000
1-17/32"	Fractional	1.5312
1-9/16"	Fractional	1.5625
1-19/32"	Fractional	1.5938
1-5/8"	Fractional	1.6250
1-21/32"	Fractional	1.6562
1-11/16"	Fractional	1.6875
1-23/32"	Fractional	1.7188
1-3/4"	Fractional	1.7500
1-25/32"	Fractional	1.7812
1-13/16"	Fractional	1.8125
1-27/32"	Fractional	1.8438
1-7/8"	Fractional	1.8750
1-29/32"	Fractional	1.9062
1-15/16"	Fractional	1.9375
1-31/32"	Fractional	1.9688
2"	Fractional	2.0000

352 sizes · 4 systems · a size lists only the sizes within 0.002 in of itself

Which system is which

Fractional — 1/64″ steps up to 1″, then 1/32″. The default in US shops.
Number — #80 (0.0135″) down to #1 (0.2280″). Counterintuitively, higher number = smaller bit.
Letter — A (0.2340″) through Z (0.4130″), filling the gap above the number set.
Metric — 0.1 mm steps. Increasingly the practical default even in inch shops.

On "interchangeable"

The last column lists sizes within 0.002″ of each other. That tolerance is fine for a clearance hole and wrong for anything that locates a part. If the hole will be reamed, tapped, or take a dowel pin, use the size the print calls for.

Data source and method

Sizes: ANSI fractional, number, letter and metric drill sets — factual values published in every tool catalog.
Conversion: Exact: 1 in = 25.4 mm.
Equivalence: Computed pairwise: each size lists only those within 0.002 in of itself. An earlier chain-linked version was rejected because a run of individually-compliant steps accumulated into spans far outside the tolerance.
Verification: Cross-system pairs confirmed to the fourth decimal: 1/4″ = E = 6.35 mm exactly; #7 (0.2010″) vs 5.1 mm (0.2008″) differ by 0.0002″. A generation-time assertion rejects the whole dataset if any listed pair exceeds the 0.002 in tolerance.
Original work: The four-system merge, diameter sort and equivalence grouping are this site's editorial structure, not a reproduction of any published table.

Related charts

Tap drill size chart — which of these bits to use before tapping
Thread size chart — the thread geometry behind those numbers