Drill Bit Size Chart

Q: How do I find the closest drill to a metric size?

Type it in the search box with "mm", for example **5.1 mm**. The answer card shows the closest number, letter or fractional drill, how far off it is, and the exact metric drill if you have one.

Number, letter, fraction and metric drills in one list, sorted by size. Type any size, decimal or millimetre to find the closest drill.

SP-DB-01

SizePlate

Closest drill to 5.1 mm

#7 drill

5.11 mm

.2010″ · +0.01 mm over

Next smaller: #8 · .1990
Next larger: 13/64 · .2031
Metric drill: 5.1 mm · .2008
Standard for: #10 free fit, 1/4-20 tap

Drill	Type	Decimal in	mm	Standard for
#80	Number	.0135	0.34
#79	Number	.0145	0.37
1/64	Fraction	.0156	0.4
#78	Number	.0160	0.41
#77	Number	.0180	0.46
0.5 mm	Metric	.0197	0.5
#76	Number	.0200	0.51
#75	Number	.0210	0.53
#74	Number	.0225	0.57
0.6 mm	Metric	.0236	0.6
#73	Number	.0240	0.61
#72	Number	.0250	0.64
#71	Number	.0260	0.66
0.7 mm	Metric	.0276	0.7
#70	Number	.0280	0.71
#69	Number	.0292	0.74
#68	Number	.0310	0.79
1/32	Fraction	.0313	0.8
0.8 mm	Metric	.0315	0.8
#67	Number	.0320	0.81
#66	Number	.0330	0.84
#65	Number	.0350	0.89
0.9 mm	Metric	.0354	0.9
#64	Number	.0360	0.91
#63	Number	.0370	0.94
#62	Number	.0380	0.97
#61	Number	.0390	0.99
1 mm	Metric	.0394	1
#60	Number	.0400	1.02
#59	Number	.0410	1.04
#58	Number	.0420	1.07
#57	Number	.0430	1.09
1.1 mm	Metric	.0433	1.1
#56	Number	.0465	1.18
3/64	Fraction	.0469	1.19	#0-80 tap
1.2 mm	Metric	.0472	1.2
1.25 mm	Metric	.0492	1.25	M1.6 × 0.35 tap
1.3 mm	Metric	.0512	1.3
#55	Number	.0520	1.32
#54	Number	.0550	1.4
1.4 mm	Metric	.0551	1.4
1.5 mm	Metric	.0591	1.5
#53	Number	.0595	1.51	#1-64 tap, #1-72 tap
1/16	Fraction	.0625	1.59
1.6 mm	Metric	.0630	1.6	M2 × 0.4 tap
#52	Number	.0635	1.61	#0 close fit
1.7 mm	Metric	.0669	1.7
#51	Number	.0670	1.7
#50	Number	.0700	1.78	#0 free fit, #2-56 tap, #2-64 tap
1.8 mm	Metric	.0709	1.8
#49	Number	.0730	1.85
1.9 mm	Metric	.0748	1.9
#48	Number	.0760	1.93	#1 close fit
5/64	Fraction	.0781	1.98
#47	Number	.0785	1.99	#3-48 tap
2 mm	Metric	.0787	2
2.05 mm	Metric	.0807	2.05	M2.5 × 0.45 tap
#46	Number	.0810	2.06	#1 free fit
#45	Number	.0820	2.08	#3-56 tap
2.1 mm	Metric	.0827	2.1
#44	Number	.0860	2.18
2.2 mm	Metric	.0866	2.2
#43	Number	.0890	2.26	#2 close fit, #4-40 tap
2.3 mm	Metric	.0906	2.3
#42	Number	.0935	2.37	#4-48 tap
3/32	Fraction	.0938	2.38
2.4 mm	Metric	.0945	2.4
#41	Number	.0960	2.44	#2 free fit
#40	Number	.0980	2.49
2.5 mm	Metric	.0984	2.5	M3 × 0.5 tap
#39	Number	.0995	2.53
#38	Number	.1015	2.58	#5-40 tap
2.6 mm	Metric	.1024	2.6
#37	Number	.1040	2.64	#3 close fit, #5-44 tap
2.65 mm	Metric	.1043	2.65	M3 × 0.35 tap
2.7 mm	Metric	.1063	2.7
#36	Number	.1065	2.71	#6-32 tap
7/64	Fraction	.1094	2.78
#35	Number	.1100	2.79	#3 free fit
2.8 mm	Metric	.1102	2.8
#34	Number	.1110	2.82
#33	Number	.1130	2.87	#6-40 tap
2.9 mm	Metric	.1142	2.9
#32	Number	.1160	2.95	#4 close fit
3 mm	Metric	.1181	3
#31	Number	.1200	3.05
3.1 mm	Metric	.1220	3.1
1/8	Fraction	.1250	3.17
3.2 mm	Metric	.1260	3.2
#30	Number	.1285	3.26	#4 free fit, #5 close fit
3.3 mm	Metric	.1299	3.3	M4 × 0.7 tap
3.4 mm	Metric	.1339	3.4
#29	Number	.1360	3.45	#5 free fit, #8-32 tap, #8-36 tap
3.5 mm	Metric	.1378	3.5	M4 × 0.5 tap
#28	Number	.1405	3.57
9/64	Fraction	.1406	3.57
3.6 mm	Metric	.1417	3.6
#27	Number	.1440	3.66	#6 close fit
3.7 mm	Metric	.1457	3.7
#26	Number	.1470	3.73
#25	Number	.1495	3.8	#6 free fit, #10-24 tap
3.8 mm	Metric	.1496	3.8
#24	Number	.1520	3.86
3.9 mm	Metric	.1535	3.9
#23	Number	.1540	3.91
5/32	Fraction	.1563	3.97
#22	Number	.1570	3.99
4 mm	Metric	.1575	4
#21	Number	.1590	4.04	#10-32 tap
#20	Number	.1610	4.09
4.1 mm	Metric	.1614	4.1
4.2 mm	Metric	.1654	4.2	M5 × 0.8 tap
#19	Number	.1660	4.22
4.3 mm	Metric	.1693	4.3
#18	Number	.1695	4.31	#8 close fit
11/64	Fraction	.1719	4.37
#17	Number	.1730	4.39
4.4 mm	Metric	.1732	4.4
#16	Number	.1770	4.5	#8 free fit, #12-24 tap
4.5 mm	Metric	.1772	4.5	M5 × 0.5 tap
#15	Number	.1800	4.57
4.6 mm	Metric	.1811	4.6
#14	Number	.1820	4.62	#12-28 tap
#13	Number	.1850	4.7
4.7 mm	Metric	.1850	4.7
3/16	Fraction	.1875	4.76
4.8 mm	Metric	.1890	4.8
#12	Number	.1890	4.8
#11	Number	.1910	4.85
4.9 mm	Metric	.1929	4.9
#10	Number	.1935	4.91
#9	Number	.1960	4.98	#10 close fit
5 mm	Metric	.1969	5	M6 × 1.0 tap
#8	Number	.1990	5.05
5.1 mm	Metric	.2008	5.1
#7	Number	.2010	5.11	#10 free fit, 1/4-20 tap
13/64	Fraction	.2031	5.16
#6	Number	.2040	5.18
5.2 mm	Metric	.2047	5.2	M6 × 0.75 tap
#5	Number	.2055	5.22
5.3 mm	Metric	.2087	5.3
#4	Number	.2090	5.31
5.4 mm	Metric	.2126	5.4
#3	Number	.2130	5.41	1/4-28 tap
5.5 mm	Metric	.2165	5.5
7/32	Fraction	.2188	5.56
5.6 mm	Metric	.2205	5.6
#2	Number	.2210	5.61	#12 close fit
5.7 mm	Metric	.2244	5.7
#1	Number	.2280	5.79	#12 free fit
5.8 mm	Metric	.2283	5.8
5.9 mm	Metric	.2323	5.9
A	Letter	.2340	5.94
15/64	Fraction	.2344	5.95
6 mm	Metric	.2362	6
B	Letter	.2380	6.05
6.1 mm	Metric	.2402	6.1
C	Letter	.2420	6.15
6.2 mm	Metric	.2441	6.2
D	Letter	.2460	6.25
6.3 mm	Metric	.2480	6.3
1/4	Fraction	.2500	6.35
E	Letter	.2500	6.35
6.4 mm	Metric	.2520	6.4
6.5 mm	Metric	.2559	6.5
F	Letter	.2570	6.53	1/4 close fit, 5/16-18 tap
6.6 mm	Metric	.2598	6.6
G	Letter	.2610	6.63
6.7 mm	Metric	.2638	6.7
17/64	Fraction	.2656	6.75
H	Letter	.2660	6.76	1/4 free fit
6.8 mm	Metric	.2677	6.8	M8 × 1.25 tap
6.9 mm	Metric	.2717	6.9
I	Letter	.2720	6.91	5/16-24 tap
7 mm	Metric	.2756	7	M8 × 1.0 tap
J	Letter	.2770	7.04
7.1 mm	Metric	.2795	7.1
K	Letter	.2810	7.14
9/32	Fraction	.2813	7.15
7.2 mm	Metric	.2835	7.2
7.3 mm	Metric	.2874	7.3
L	Letter	.2900	7.37
7.4 mm	Metric	.2913	7.4
M	Letter	.2950	7.49
7.5 mm	Metric	.2953	7.5
19/64	Fraction	.2969	7.54
7.6 mm	Metric	.2992	7.6
N	Letter	.3020	7.67
7.7 mm	Metric	.3031	7.7
7.8 mm	Metric	.3071	7.8
7.9 mm	Metric	.3110	7.9
5/16	Fraction	.3125	7.94	3/8-16 tap
8 mm	Metric	.3150	8
O	Letter	.3160	8.03
8.1 mm	Metric	.3189	8.1
8.2 mm	Metric	.3228	8.2
P	Letter	.3230	8.2	5/16 close fit
8.3 mm	Metric	.3268	8.3
21/64	Fraction	.3281	8.33
8.4 mm	Metric	.3307	8.4
Q	Letter	.3320	8.43	5/16 free fit, 3/8-24 tap
8.5 mm	Metric	.3346	8.5	M10 × 1.5 tap
8.6 mm	Metric	.3386	8.6
R	Letter	.3390	8.61
8.7 mm	Metric	.3425	8.7
11/32	Fraction	.3438	8.73
8.8 mm	Metric	.3465	8.8	M10 × 1.25 tap
S	Letter	.3480	8.84
8.9 mm	Metric	.3504	8.9
9 mm	Metric	.3543	9	M10 × 1.0 tap
T	Letter	.3580	9.09
9.1 mm	Metric	.3583	9.1
23/64	Fraction	.3594	9.13
9.2 mm	Metric	.3622	9.2
9.3 mm	Metric	.3661	9.3
U	Letter	.3680	9.35	7/16-14 tap
9.4 mm	Metric	.3701	9.4
9.5 mm	Metric	.3740	9.5
3/8	Fraction	.3750	9.52
V	Letter	.3770	9.58
9.6 mm	Metric	.3780	9.6
9.7 mm	Metric	.3819	9.7
9.8 mm	Metric	.3858	9.8
W	Letter	.3860	9.8	3/8 close fit
9.9 mm	Metric	.3898	9.9
25/64	Fraction	.3906	9.92	7/16-20 tap
10 mm	Metric	.3937	10
X	Letter	.3970	10.08	3/8 free fit
10.1 mm	Metric	.3976	10.1
10.2 mm	Metric	.4016	10.2	M12 × 1.75 tap
Y	Letter	.4040	10.26
10.3 mm	Metric	.4055	10.3
13/32	Fraction	.4063	10.32
10.4 mm	Metric	.4094	10.4
Z	Letter	.4130	10.49
10.5 mm	Metric	.4134	10.5	M12 × 1.5 tap
10.6 mm	Metric	.4173	10.6
10.7 mm	Metric	.4213	10.7
27/64	Fraction	.4219	10.72	1/2-13 tap
10.8 mm	Metric	.4252	10.8	M12 × 1.25 tap
10.9 mm	Metric	.4291	10.9
11 mm	Metric	.4331	11
11.1 mm	Metric	.4370	11.1
7/16	Fraction	.4375	11.11
11.2 mm	Metric	.4409	11.2
11.3 mm	Metric	.4449	11.3
11.4 mm	Metric	.4488	11.4
11.5 mm	Metric	.4528	11.5
29/64	Fraction	.4531	11.51	7/16 close fit, 1/2-20 tap
11.6 mm	Metric	.4567	11.6
11.7 mm	Metric	.4606	11.7
11.8 mm	Metric	.4646	11.8
11.9 mm	Metric	.4685	11.9
15/32	Fraction	.4688	11.91	7/16 free fit
12 mm	Metric	.4724	12	M14 × 2.0 tap
12.1 mm	Metric	.4764	12.1
12.2 mm	Metric	.4803	12.2
12.3 mm	Metric	.4843	12.3
31/64	Fraction	.4844	12.3	9/16-12 tap
12.4 mm	Metric	.4882	12.4
12.5 mm	Metric	.4921	12.5	M14 × 1.5 tap
12.6 mm	Metric	.4961	12.6
1/2	Fraction	.5000	12.7
12.7 mm	Metric	.5000	12.7
12.8 mm	Metric	.5039	12.8
12.9 mm	Metric	.5079	12.9
13 mm	Metric	.5118	13
33/64	Fraction	.5156	13.1	1/2 close fit, 9/16-18 tap
17/32	Fraction	.5313	13.5	1/2 free fit, 5/8-11 tap
13.5 mm	Metric	.5315	13.5
35/64	Fraction	.5469	13.89
14 mm	Metric	.5512	14	M16 × 2.0 tap
9/16	Fraction	.5625	14.29
14.5 mm	Metric	.5709	14.5	M16 × 1.5 tap
37/64	Fraction	.5781	14.68	9/16 close fit, 5/8-18 tap
15 mm	Metric	.5906	15
19/32	Fraction	.5938	15.08	9/16 free fit
39/64	Fraction	.6094	15.48
15.5 mm	Metric	.6102	15.5
5/8	Fraction	.6250	15.88
16 mm	Metric	.6299	16
41/64	Fraction	.6406	16.27	5/8 close fit
16.5 mm	Metric	.6496	16.5
21/32	Fraction	.6563	16.67	5/8 free fit, 3/4-10 tap
17 mm	Metric	.6693	17
43/64	Fraction	.6719	17.07
11/16	Fraction	.6875	17.46	3/4-16 tap
17.5 mm	Metric	.6890	17.5	M20 × 2.5 tap
45/64	Fraction	.7031	17.86
18 mm	Metric	.7087	18
23/32	Fraction	.7188	18.26
18.5 mm	Metric	.7283	18.5	M20 × 1.5 tap
47/64	Fraction	.7344	18.65
19 mm	Metric	.7480	19
3/4	Fraction	.7500	19.05
49/64	Fraction	.7656	19.45	3/4 close fit, 7/8-9 tap
19.5 mm	Metric	.7677	19.5
25/32	Fraction	.7813	19.85	3/4 free fit
20 mm	Metric	.7874	20
51/64	Fraction	.7969	20.24
20.5 mm	Metric	.8071	20.5
13/16	Fraction	.8125	20.64	7/8-14 tap
21 mm	Metric	.8268	21	M24 × 3.0 tap
53/64	Fraction	.8281	21.03
27/32	Fraction	.8438	21.43
21.5 mm	Metric	.8465	21.5
55/64	Fraction	.8594	21.83
22 mm	Metric	.8661	22	M24 × 2.0 tap
7/8	Fraction	.8750	22.22	1-8 tap
22.5 mm	Metric	.8858	22.5
57/64	Fraction	.8906	22.62	7/8 close fit
23 mm	Metric	.9055	23
29/32	Fraction	.9063	23.02	7/8 free fit
59/64	Fraction	.9219	23.42	1-12 tap
23.5 mm	Metric	.9252	23.5
15/16	Fraction	.9375	23.81
24 mm	Metric	.9449	24
61/64	Fraction	.9531	24.21
24.5 mm	Metric	.9646	24.5
31/32	Fraction	.9688	24.61
25 mm	Metric	.9843	25
63/64	Fraction	.9844	25
1	Fraction	1.0000	25.4
1-1/64	Fraction	1.0156	25.8	1 close fit
1-1/32	Fraction	1.0313	26.2	1 free fit

Drill	in	mm
#80	.0135	0.34
#79	.0145	0.37
1/64	.0156	0.4
#78	.0160	0.41
#77	.0180	0.46
0.5 mm	.0197	0.5
#76	.0200	0.51
#75	.0210	0.53
#74	.0225	0.57
0.6 mm	.0236	0.6
#73	.0240	0.61
#72	.0250	0.64
#71	.0260	0.66
0.7 mm	.0276	0.7
#70	.0280	0.71
#69	.0292	0.74
#68	.0310	0.79
1/32	.0313	0.8
0.8 mm	.0315	0.8
#67	.0320	0.81
#66	.0330	0.84
#65	.0350	0.89
0.9 mm	.0354	0.9
#64	.0360	0.91
#63	.0370	0.94
#62	.0380	0.97
#61	.0390	0.99
1 mm	.0394	1
#60	.0400	1.02
#59	.0410	1.04
#58	.0420	1.07
#57	.0430	1.09
1.1 mm	.0433	1.1
#56	.0465	1.18
3/64	.0469	1.19
1.2 mm	.0472	1.2
1.25 mm	.0492	1.25
1.3 mm	.0512	1.3
#55	.0520	1.32
#54	.0550	1.4
1.4 mm	.0551	1.4
1.5 mm	.0591	1.5
#53	.0595	1.51
1/16	.0625	1.59
1.6 mm	.0630	1.6
#52	.0635	1.61
1.7 mm	.0669	1.7
#51	.0670	1.7
#50	.0700	1.78
1.8 mm	.0709	1.8
#49	.0730	1.85
1.9 mm	.0748	1.9
#48	.0760	1.93
5/64	.0781	1.98
#47	.0785	1.99
2 mm	.0787	2
2.05 mm	.0807	2.05
#46	.0810	2.06
#45	.0820	2.08
2.1 mm	.0827	2.1
#44	.0860	2.18
2.2 mm	.0866	2.2
#43	.0890	2.26
2.3 mm	.0906	2.3
#42	.0935	2.37
3/32	.0938	2.38
2.4 mm	.0945	2.4
#41	.0960	2.44
#40	.0980	2.49
2.5 mm	.0984	2.5
#39	.0995	2.53
#38	.1015	2.58
2.6 mm	.1024	2.6
#37	.1040	2.64
2.65 mm	.1043	2.65
2.7 mm	.1063	2.7
#36	.1065	2.71
7/64	.1094	2.78
#35	.1100	2.79
2.8 mm	.1102	2.8
#34	.1110	2.82
#33	.1130	2.87
2.9 mm	.1142	2.9
#32	.1160	2.95
3 mm	.1181	3
#31	.1200	3.05
3.1 mm	.1220	3.1
1/8	.1250	3.17
3.2 mm	.1260	3.2
#30	.1285	3.26
3.3 mm	.1299	3.3
3.4 mm	.1339	3.4
#29	.1360	3.45
3.5 mm	.1378	3.5
#28	.1405	3.57
9/64	.1406	3.57
3.6 mm	.1417	3.6
#27	.1440	3.66
3.7 mm	.1457	3.7
#26	.1470	3.73
#25	.1495	3.8
3.8 mm	.1496	3.8
#24	.1520	3.86
3.9 mm	.1535	3.9
#23	.1540	3.91
5/32	.1563	3.97
#22	.1570	3.99
4 mm	.1575	4
#21	.1590	4.04

Drill	in	mm
#20	.1610	4.09
4.1 mm	.1614	4.1
4.2 mm	.1654	4.2
#19	.1660	4.22
4.3 mm	.1693	4.3
#18	.1695	4.31
11/64	.1719	4.37
#17	.1730	4.39
4.4 mm	.1732	4.4
#16	.1770	4.5
4.5 mm	.1772	4.5
#15	.1800	4.57
4.6 mm	.1811	4.6
#14	.1820	4.62
#13	.1850	4.7
4.7 mm	.1850	4.7
3/16	.1875	4.76
4.8 mm	.1890	4.8
#12	.1890	4.8
#11	.1910	4.85
4.9 mm	.1929	4.9
#10	.1935	4.91
#9	.1960	4.98
5 mm	.1969	5
#8	.1990	5.05
5.1 mm	.2008	5.1
#7	.2010	5.11
13/64	.2031	5.16
#6	.2040	5.18
5.2 mm	.2047	5.2
#5	.2055	5.22
5.3 mm	.2087	5.3
#4	.2090	5.31
5.4 mm	.2126	5.4
#3	.2130	5.41
5.5 mm	.2165	5.5
7/32	.2188	5.56
5.6 mm	.2205	5.6
#2	.2210	5.61
5.7 mm	.2244	5.7
#1	.2280	5.79
5.8 mm	.2283	5.8
5.9 mm	.2323	5.9
A	.2340	5.94
15/64	.2344	5.95
6 mm	.2362	6
B	.2380	6.05
6.1 mm	.2402	6.1
C	.2420	6.15
6.2 mm	.2441	6.2
D	.2460	6.25
6.3 mm	.2480	6.3
1/4	.2500	6.35
E	.2500	6.35
6.4 mm	.2520	6.4
6.5 mm	.2559	6.5
F	.2570	6.53
6.6 mm	.2598	6.6
G	.2610	6.63
6.7 mm	.2638	6.7
17/64	.2656	6.75
H	.2660	6.76
6.8 mm	.2677	6.8
6.9 mm	.2717	6.9
I	.2720	6.91
7 mm	.2756	7
J	.2770	7.04
7.1 mm	.2795	7.1
K	.2810	7.14
9/32	.2813	7.15
7.2 mm	.2835	7.2
7.3 mm	.2874	7.3
L	.2900	7.37
7.4 mm	.2913	7.4
M	.2950	7.49
7.5 mm	.2953	7.5
19/64	.2969	7.54
7.6 mm	.2992	7.6
N	.3020	7.67
7.7 mm	.3031	7.7
7.8 mm	.3071	7.8
7.9 mm	.3110	7.9
5/16	.3125	7.94
8 mm	.3150	8
O	.3160	8.03
8.1 mm	.3189	8.1
8.2 mm	.3228	8.2
P	.3230	8.2
8.3 mm	.3268	8.3
21/64	.3281	8.33
8.4 mm	.3307	8.4
Q	.3320	8.43
8.5 mm	.3346	8.5
8.6 mm	.3386	8.6
R	.3390	8.61
8.7 mm	.3425	8.7
11/32	.3438	8.73
8.8 mm	.3465	8.8
S	.3480	8.84
8.9 mm	.3504	8.9
9 mm	.3543	9
T	.3580	9.09
9.1 mm	.3583	9.1
23/64	.3594	9.13
9.2 mm	.3622	9.2
9.3 mm	.3661	9.3
U	.3680	9.35
9.4 mm	.3701	9.4
9.5 mm	.3740	9.5

Drill	in	mm
3/8	.3750	9.52
V	.3770	9.58
9.6 mm	.3780	9.6
9.7 mm	.3819	9.7
9.8 mm	.3858	9.8
W	.3860	9.8
9.9 mm	.3898	9.9
25/64	.3906	9.92
10 mm	.3937	10
X	.3970	10.08
10.1 mm	.3976	10.1
10.2 mm	.4016	10.2
Y	.4040	10.26
10.3 mm	.4055	10.3
13/32	.4063	10.32
10.4 mm	.4094	10.4
Z	.4130	10.49
10.5 mm	.4134	10.5
10.6 mm	.4173	10.6
10.7 mm	.4213	10.7
27/64	.4219	10.72
10.8 mm	.4252	10.8
10.9 mm	.4291	10.9
11 mm	.4331	11
11.1 mm	.4370	11.1
7/16	.4375	11.11
11.2 mm	.4409	11.2
11.3 mm	.4449	11.3
11.4 mm	.4488	11.4
11.5 mm	.4528	11.5
29/64	.4531	11.51
11.6 mm	.4567	11.6
11.7 mm	.4606	11.7
11.8 mm	.4646	11.8
11.9 mm	.4685	11.9
15/32	.4688	11.91
12 mm	.4724	12
12.1 mm	.4764	12.1
12.2 mm	.4803	12.2
12.3 mm	.4843	12.3
31/64	.4844	12.3
12.4 mm	.4882	12.4
12.5 mm	.4921	12.5
12.6 mm	.4961	12.6
1/2	.5000	12.7
12.7 mm	.5000	12.7
12.8 mm	.5039	12.8
12.9 mm	.5079	12.9
13 mm	.5118	13
33/64	.5156	13.1
17/32	.5313	13.5
13.5 mm	.5315	13.5
35/64	.5469	13.89
14 mm	.5512	14
9/16	.5625	14.29
14.5 mm	.5709	14.5
37/64	.5781	14.68
15 mm	.5906	15
19/32	.5938	15.08
39/64	.6094	15.48
15.5 mm	.6102	15.5
5/8	.6250	15.88
16 mm	.6299	16
41/64	.6406	16.27
16.5 mm	.6496	16.5
21/32	.6563	16.67
17 mm	.6693	17
43/64	.6719	17.07
11/16	.6875	17.46
17.5 mm	.6890	17.5
45/64	.7031	17.86
18 mm	.7087	18
23/32	.7188	18.26
18.5 mm	.7283	18.5
47/64	.7344	18.65
19 mm	.7480	19
3/4	.7500	19.05
49/64	.7656	19.45
19.5 mm	.7677	19.5
25/32	.7813	19.85
20 mm	.7874	20
51/64	.7969	20.24
20.5 mm	.8071	20.5
13/16	.8125	20.64
21 mm	.8268	21
53/64	.8281	21.03
27/32	.8438	21.43
21.5 mm	.8465	21.5
55/64	.8594	21.83
22 mm	.8661	22
7/8	.8750	22.22
22.5 mm	.8858	22.5
57/64	.8906	22.62
23 mm	.9055	23
29/32	.9063	23.02
59/64	.9219	23.42
23.5 mm	.9252	23.5
15/16	.9375	23.81
24 mm	.9449	24
61/64	.9531	24.21
24.5 mm	.9646	24.5
31/32	.9688	24.61
25 mm	.9843	25
63/64	.9844	25
1	1.0000	25.4
1-1/64	1.0156	25.8
1-1/32	1.0313	26.2

Chart

SP-DB-01

Standard

ASME B94.11M

Rev

A · Oct 2026

Checked

2 references · sources

Number drills (#80 smallest to #1) and letter drills (A to Z) fill the gaps between fractional sizes. E is exactly 1/4″.

Why Four Drill Systems?

Fractional drills step in 1/64″ (.0156″). Number drills (#80 smallest to #1) and letter drills (A to Z) fill the gaps between them, so there’s a drill within a few thousandths of any inch size you need. Metric drills step in 0.1 mm.

Sorted together, as above, you can see which drills are near-duplicates: E is exactly 1/4″, a 5.1 mm drill is within .0002″ of a #7, and 5 mm sits between #9 and #8.

Reading a Size

Decimal inches like .201 or 0.201 find the closest inch drill.
Millimetres like 5.1 mm do the same and show the gap in mm.
A bare number reads as inches below 1.5 and as millimetres from 1.5 up.
A drill name like #29, F or 13/64 jumps straight to that drill.

Questions

What size is a

Which is bigger, a number drill or a letter drill?

Every letter drill is bigger than every number drill. Number drills run from

How do I find the closest drill to a metric size?

Type it in the search box with “mm”, for example 5.1 mm. The answer card shows the closest number, letter or fractional drill, how far off it is, and the exact metric drill if you have one.