DIMENSIONAL REFERENCE

Drill size chart

Read each drill’s cutting diameter in millimetres and inches. Number and letter designations are catalogue names, not measurement units.

Choose a size to compare nearby dimensions. ≈ marks decimal inches rounded to six places.

Number drills

Number designations #80 through #1, listed from smaller to larger cutting diameter.

Number drills · 80 sizes
Size Open on chart ↗	Millimetres	Decimal inches
#80	0.3429	0.0135″
#79	0.3683	0.0145″
#78	0.4064	0.016″
#77	0.4572	0.018″
#76	0.508	0.02″
#75	0.5334	0.021″
#74	0.5715	0.0225″
#73	0.6096	0.024″
#72	0.635	0.025″
#71	0.6604	0.026″
#70	0.7112	0.028″
#69	0.74168	0.0292″
#68	0.7874	0.031″
#67	0.8128	0.032″
#66	0.8382	0.033″
#65	0.889	0.035″
#64	0.9144	0.036″
#63	0.9398	0.037″
#62	0.9652	0.038″
#61	0.9906	0.039″
#60	1.016	0.04″
#59	1.0414	0.041″
#58	1.0668	0.042″
#57	1.0922	0.043″
#56	1.1811	0.0465″
#55	1.3208	0.052″
#54	1.397	0.055″
#53	1.5113	0.0595″
#52	1.6129	0.0635″
#51	1.7018	0.067″
#50	1.778	0.07″
#49	1.8542	0.073″
#48	1.9304	0.076″
#47	1.9939	0.0785″
#46	2.0574	0.081″
#45	2.0828	0.082″
#44	2.1844	0.086″
#43	2.2606	0.089″
#42	2.3749	0.0935″
#41	2.4384	0.096″
#40	2.4892	0.098″
#39	2.5273	0.0995″
#38	2.5781	0.1015″
#37	2.6416	0.104″
#36	2.7051	0.1065″
#35	2.794	0.11″
#34	2.8194	0.111″
#33	2.8702	0.113″
#32	2.9464	0.116″
#31	3.048	0.12″
#30	3.2639	0.1285″
#29	3.4544	0.136″
#28	3.5687	0.1405″
#27	3.6576	0.144″
#26	3.7338	0.147″
#25	3.7973	0.1495″
#24	3.8608	0.152″
#23	3.9116	0.154″
#22	3.9878	0.157″
#21	4.0386	0.159″
#20	4.0894	0.161″
#19	4.2164	0.166″
#18	4.3053	0.1695″
#17	4.3942	0.173″
#16	4.4958	0.177″
#15	4.572	0.18″
#14	4.6228	0.182″
#13	4.699	0.185″
#12	4.8006	0.189″
#11	4.8514	0.191″
#10	4.9149	0.1935″
#9	4.9784	0.196″
#8	5.0546	0.199″
#7	5.1054	0.201″
#6	5.1816	0.204″
#5	5.2197	0.2055″
#4	5.3086	0.209″
#3	5.4102	0.213″
#2	5.6134	0.221″
#1	5.7912	0.228″

Letter drills

Letter designations A through Z, listed by cutting diameter.

Letter drills · 26 sizes
Size Open on chart ↗	Millimetres	Decimal inches
A	5.9436	0.234″
B	6.0452	0.238″
C	6.1468	0.242″
D	6.2484	0.246″
E	6.35	0.25″
F	6.5278	0.257″
G	6.6294	0.261″
H	6.7564	0.266″
I	6.9088	0.272″
J	7.0358	0.277″
K	7.1374	0.281″
L	7.366	0.29″
M	7.493	0.295″
N	7.6708	0.302″
O	8.0264	0.316″
P	8.2042	0.323″
Q	8.4328	0.332″
R	8.6106	0.339″
S	8.8392	0.348″
T	9.0932	0.358″
U	9.3472	0.368″
V	9.5758	0.377″
W	9.8044	0.386″
X	10.0838	0.397″
Y	10.2616	0.404″
Z	10.4902	0.413″

Fractional drills

Every 1/64 inch from 1/64″ through 1″. These decimal-inch and millimetre conversions are exact.

Fractional drills · 64 sizes
Size Open on chart ↗	Millimetres	Decimal inches
1/64″	0.396875	0.015625″
1/32″	0.79375	0.03125″
3/64″	1.190625	0.046875″
1/16″	1.5875	0.0625″
5/64″	1.984375	0.078125″
3/32″	2.38125	0.09375″
7/64″	2.778125	0.109375″
1/8″	3.175	0.125″
9/64″	3.571875	0.140625″
5/32″	3.96875	0.15625″
11/64″	4.365625	0.171875″
3/16″	4.7625	0.1875″
13/64″	5.159375	0.203125″
7/32″	5.55625	0.21875″
15/64″	5.953125	0.234375″
1/4″	6.35	0.25″
17/64″	6.746875	0.265625″
9/32″	7.14375	0.28125″
19/64″	7.540625	0.296875″
5/16″	7.9375	0.3125″
21/64″	8.334375	0.328125″
11/32″	8.73125	0.34375″
23/64″	9.128125	0.359375″
3/8″	9.525	0.375″
25/64″	9.921875	0.390625″
13/32″	10.31875	0.40625″
27/64″	10.715625	0.421875″
7/16″	11.1125	0.4375″
29/64″	11.509375	0.453125″
15/32″	11.90625	0.46875″
31/64″	12.303125	0.484375″
1/2″	12.7	0.5″
33/64″	13.096875	0.515625″
17/32″	13.49375	0.53125″
35/64″	13.890625	0.546875″
9/16″	14.2875	0.5625″
37/64″	14.684375	0.578125″
19/32″	15.08125	0.59375″
39/64″	15.478125	0.609375″
5/8″	15.875	0.625″
41/64″	16.271875	0.640625″
21/32″	16.66875	0.65625″
43/64″	17.065625	0.671875″
11/16″	17.4625	0.6875″
45/64″	17.859375	0.703125″
23/32″	18.25625	0.71875″
47/64″	18.653125	0.734375″
3/4″	19.05	0.75″
49/64″	19.446875	0.765625″
25/32″	19.84375	0.78125″
51/64″	20.240625	0.796875″
13/16″	20.6375	0.8125″
53/64″	21.034375	0.828125″
27/32″	21.43125	0.84375″
55/64″	21.828125	0.859375″
7/8″	22.225	0.875″
57/64″	22.621875	0.890625″
29/32″	23.01875	0.90625″
59/64″	23.415625	0.921875″
15/16″	23.8125	0.9375″
61/64″	24.209375	0.953125″
31/32″	24.60625	0.96875″
63/64″	25.003125	0.984375″
1″	25.4	1″

Selected metric drills

Selected metric sizes from 0.3 through 40.5 mm. This is not a claim of stock availability or every manufactured drill size.

Selected metric drills · 290 sizes
Size Open on chart ↗	Millimetres	Decimal inches
0.3 mm	0.3	≈ 0.011811″
0.32 mm	0.32	≈ 0.012598″
0.35 mm	0.35	≈ 0.01378″
0.38 mm	0.38	≈ 0.014961″
0.4 mm	0.4	≈ 0.015748″
0.42 mm	0.42	≈ 0.016535″
0.45 mm	0.45	≈ 0.017717″
0.48 mm	0.48	≈ 0.018898″
0.5 mm	0.5	≈ 0.019685″
0.52 mm	0.52	≈ 0.020472″
0.55 mm	0.55	≈ 0.021654″
0.58 mm	0.58	≈ 0.022835″
0.6 mm	0.6	≈ 0.023622″
0.62 mm	0.62	≈ 0.024409″
0.65 mm	0.65	≈ 0.025591″
0.68 mm	0.68	≈ 0.026772″
0.7 mm	0.7	≈ 0.027559″
0.72 mm	0.72	≈ 0.028346″
0.75 mm	0.75	≈ 0.029528″
0.78 mm	0.78	≈ 0.030709″
0.8 mm	0.8	≈ 0.031496″
0.82 mm	0.82	≈ 0.032283″
0.85 mm	0.85	≈ 0.033465″
0.88 mm	0.88	≈ 0.034646″
0.9 mm	0.9	≈ 0.035433″
0.92 mm	0.92	≈ 0.03622″
0.95 mm	0.95	≈ 0.037402″
0.98 mm	0.98	≈ 0.038583″
1 mm	1	≈ 0.03937″
1.05 mm	1.05	≈ 0.041339″
1.1 mm	1.1	≈ 0.043307″
1.15 mm	1.15	≈ 0.045276″
1.2 mm	1.2	≈ 0.047244″
1.25 mm	1.25	≈ 0.049213″
1.3 mm	1.3	≈ 0.051181″
1.35 mm	1.35	≈ 0.05315″
1.4 mm	1.4	≈ 0.055118″
1.45 mm	1.45	≈ 0.057087″
1.5 mm	1.5	≈ 0.059055″
1.55 mm	1.55	≈ 0.061024″
1.6 mm	1.6	≈ 0.062992″
1.65 mm	1.65	≈ 0.064961″
1.7 mm	1.7	≈ 0.066929″
1.75 mm	1.75	≈ 0.068898″
1.8 mm	1.8	≈ 0.070866″
1.85 mm	1.85	≈ 0.072835″
1.9 mm	1.9	≈ 0.074803″
1.95 mm	1.95	≈ 0.076772″
2 mm	2	≈ 0.07874″
2.05 mm	2.05	≈ 0.080709″
2.1 mm	2.1	≈ 0.082677″
2.15 mm	2.15	≈ 0.084646″
2.2 mm	2.2	≈ 0.086614″
2.25 mm	2.25	≈ 0.088583″
2.3 mm	2.3	≈ 0.090551″
2.35 mm	2.35	≈ 0.09252″
2.4 mm	2.4	≈ 0.094488″
2.45 mm	2.45	≈ 0.096457″
2.5 mm	2.5	≈ 0.098425″
2.55 mm	2.55	≈ 0.100394″
2.6 mm	2.6	≈ 0.102362″
2.65 mm	2.65	≈ 0.104331″
2.7 mm	2.7	≈ 0.106299″
2.75 mm	2.75	≈ 0.108268″
2.8 mm	2.8	≈ 0.110236″
2.85 mm	2.85	≈ 0.112205″
2.9 mm	2.9	≈ 0.114173″
2.95 mm	2.95	≈ 0.116142″
3 mm	3	≈ 0.11811″
3.1 mm	3.1	≈ 0.122047″
3.2 mm	3.2	≈ 0.125984″
3.25 mm	3.25	≈ 0.127953″
3.3 mm	3.3	≈ 0.129921″
3.4 mm	3.4	≈ 0.133858″
3.5 mm	3.5	≈ 0.137795″
3.6 mm	3.6	≈ 0.141732″
3.7 mm	3.7	≈ 0.145669″
3.75 mm	3.75	≈ 0.147638″
3.8 mm	3.8	≈ 0.149606″
3.9 mm	3.9	≈ 0.153543″
4 mm	4	≈ 0.15748″
4.1 mm	4.1	≈ 0.161417″
4.2 mm	4.2	≈ 0.165354″
4.25 mm	4.25	≈ 0.167323″
4.3 mm	4.3	≈ 0.169291″
4.4 mm	4.4	≈ 0.173228″
4.5 mm	4.5	≈ 0.177165″
4.6 mm	4.6	≈ 0.181102″
4.7 mm	4.7	≈ 0.185039″
4.75 mm	4.75	≈ 0.187008″
4.8 mm	4.8	≈ 0.188976″
4.9 mm	4.9	≈ 0.192913″
5 mm	5	≈ 0.19685″
5.1 mm	5.1	≈ 0.200787″
5.2 mm	5.2	≈ 0.204724″
5.25 mm	5.25	≈ 0.206693″
5.3 mm	5.3	≈ 0.208661″
5.4 mm	5.4	≈ 0.212598″
5.5 mm	5.5	≈ 0.216535″
5.6 mm	5.6	≈ 0.220472″
5.7 mm	5.7	≈ 0.224409″
5.75 mm	5.75	≈ 0.226378″
5.8 mm	5.8	≈ 0.228346″
5.9 mm	5.9	≈ 0.232283″
6 mm	6	≈ 0.23622″
6.1 mm	6.1	≈ 0.240157″
6.2 mm	6.2	≈ 0.244094″
6.25 mm	6.25	≈ 0.246063″
6.3 mm	6.3	≈ 0.248031″
6.4 mm	6.4	≈ 0.251969″
6.5 mm	6.5	≈ 0.255906″
6.6 mm	6.6	≈ 0.259843″
6.7 mm	6.7	≈ 0.26378″
6.75 mm	6.75	≈ 0.265748″
6.8 mm	6.8	≈ 0.267717″
6.9 mm	6.9	≈ 0.271654″
7 mm	7	≈ 0.275591″
7.1 mm	7.1	≈ 0.279528″
7.2 mm	7.2	≈ 0.283465″
7.25 mm	7.25	≈ 0.285433″
7.3 mm	7.3	≈ 0.287402″
7.4 mm	7.4	≈ 0.291339″
7.5 mm	7.5	≈ 0.295276″
7.6 mm	7.6	≈ 0.299213″
7.7 mm	7.7	≈ 0.30315″
7.75 mm	7.75	≈ 0.305118″
7.8 mm	7.8	≈ 0.307087″
7.9 mm	7.9	≈ 0.311024″
8 mm	8	≈ 0.314961″
8.1 mm	8.1	≈ 0.318898″
8.2 mm	8.2	≈ 0.322835″
8.25 mm	8.25	≈ 0.324803″
8.3 mm	8.3	≈ 0.326772″
8.4 mm	8.4	≈ 0.330709″
8.5 mm	8.5	≈ 0.334646″
8.6 mm	8.6	≈ 0.338583″
8.7 mm	8.7	≈ 0.34252″
8.75 mm	8.75	≈ 0.344488″
8.8 mm	8.8	≈ 0.346457″
8.9 mm	8.9	≈ 0.350394″
9 mm	9	≈ 0.354331″
9.1 mm	9.1	≈ 0.358268″
9.2 mm	9.2	≈ 0.362205″
9.25 mm	9.25	≈ 0.364173″
9.3 mm	9.3	≈ 0.366142″
9.4 mm	9.4	≈ 0.370079″
9.5 mm	9.5	≈ 0.374016″
9.6 mm	9.6	≈ 0.377953″
9.7 mm	9.7	≈ 0.38189″
9.75 mm	9.75	≈ 0.383858″
9.8 mm	9.8	≈ 0.385827″
9.9 mm	9.9	≈ 0.389764″
10 mm	10	≈ 0.393701″
10.1 mm	10.1	≈ 0.397638″
10.2 mm	10.2	≈ 0.401575″
10.25 mm	10.25	≈ 0.403543″
10.3 mm	10.3	≈ 0.405512″
10.4 mm	10.4	≈ 0.409449″
10.5 mm	10.5	≈ 0.413386″
10.6 mm	10.6	≈ 0.417323″
10.7 mm	10.7	≈ 0.42126″
10.75 mm	10.75	≈ 0.423228″
10.8 mm	10.8	≈ 0.425197″
10.9 mm	10.9	≈ 0.429134″
11 mm	11	≈ 0.433071″
11.1 mm	11.1	≈ 0.437008″
11.2 mm	11.2	≈ 0.440945″
11.25 mm	11.25	≈ 0.442913″
11.3 mm	11.3	≈ 0.444882″
11.4 mm	11.4	≈ 0.448819″
11.5 mm	11.5	≈ 0.452756″
11.6 mm	11.6	≈ 0.456693″
11.7 mm	11.7	≈ 0.46063″
11.75 mm	11.75	≈ 0.462598″
11.8 mm	11.8	≈ 0.464567″
11.9 mm	11.9	≈ 0.468504″
12 mm	12	≈ 0.472441″
12.1 mm	12.1	≈ 0.476378″
12.2 mm	12.2	≈ 0.480315″
12.25 mm	12.25	≈ 0.482283″
12.3 mm	12.3	≈ 0.484252″
12.4 mm	12.4	≈ 0.488189″
12.5 mm	12.5	≈ 0.492126″
12.6 mm	12.6	≈ 0.496063″
12.7 mm	12.7	0.5″
12.75 mm	12.75	≈ 0.501969″
12.8 mm	12.8	≈ 0.503937″
12.9 mm	12.9	≈ 0.507874″
13 mm	13	≈ 0.511811″
13.1 mm	13.1	≈ 0.515748″
13.2 mm	13.2	≈ 0.519685″
13.25 mm	13.25	≈ 0.521654″
13.3 mm	13.3	≈ 0.523622″
13.4 mm	13.4	≈ 0.527559″
13.5 mm	13.5	≈ 0.531496″
13.6 mm	13.6	≈ 0.535433″
13.7 mm	13.7	≈ 0.53937″
13.75 mm	13.75	≈ 0.541339″
13.8 mm	13.8	≈ 0.543307″
13.9 mm	13.9	≈ 0.547244″
14 mm	14	≈ 0.551181″
14.25 mm	14.25	≈ 0.561024″
14.5 mm	14.5	≈ 0.570866″
14.75 mm	14.75	≈ 0.580709″
15 mm	15	≈ 0.590551″
15.25 mm	15.25	≈ 0.600394″
15.5 mm	15.5	≈ 0.610236″
15.75 mm	15.75	≈ 0.620079″
16 mm	16	≈ 0.629921″
16.25 mm	16.25	≈ 0.639764″
16.5 mm	16.5	≈ 0.649606″
16.75 mm	16.75	≈ 0.659449″
17 mm	17	≈ 0.669291″
17.25 mm	17.25	≈ 0.679134″
17.5 mm	17.5	≈ 0.688976″
17.75 mm	17.75	≈ 0.698819″
18 mm	18	≈ 0.708661″
18.25 mm	18.25	≈ 0.718504″
18.5 mm	18.5	≈ 0.728346″
18.75 mm	18.75	≈ 0.738189″
19 mm	19	≈ 0.748031″
19.25 mm	19.25	≈ 0.757874″
19.5 mm	19.5	≈ 0.767717″
19.75 mm	19.75	≈ 0.777559″
20 mm	20	≈ 0.787402″
20.25 mm	20.25	≈ 0.797244″
20.5 mm	20.5	≈ 0.807087″
20.75 mm	20.75	≈ 0.816929″
21 mm	21	≈ 0.826772″
21.25 mm	21.25	≈ 0.836614″
21.5 mm	21.5	≈ 0.846457″
21.75 mm	21.75	≈ 0.856299″
22 mm	22	≈ 0.866142″
22.25 mm	22.25	≈ 0.875984″
22.5 mm	22.5	≈ 0.885827″
22.75 mm	22.75	≈ 0.895669″
23 mm	23	≈ 0.905512″
23.25 mm	23.25	≈ 0.915354″
23.5 mm	23.5	≈ 0.925197″
23.75 mm	23.75	≈ 0.935039″
24 mm	24	≈ 0.944882″
24.25 mm	24.25	≈ 0.954724″
24.5 mm	24.5	≈ 0.964567″
24.75 mm	24.75	≈ 0.974409″
25 mm	25	≈ 0.984252″
25.25 mm	25.25	≈ 0.994094″
25.5 mm	25.5	≈ 1.003937″
25.75 mm	25.75	≈ 1.01378″
26 mm	26	≈ 1.023622″
26.25 mm	26.25	≈ 1.033465″
26.5 mm	26.5	≈ 1.043307″
26.75 mm	26.75	≈ 1.05315″
27 mm	27	≈ 1.062992″
27.25 mm	27.25	≈ 1.072835″
27.5 mm	27.5	≈ 1.082677″
27.75 mm	27.75	≈ 1.09252″
28 mm	28	≈ 1.102362″
28.25 mm	28.25	≈ 1.112205″
28.5 mm	28.5	≈ 1.122047″
28.75 mm	28.75	≈ 1.13189″
29 mm	29	≈ 1.141732″
29.25 mm	29.25	≈ 1.151575″
29.5 mm	29.5	≈ 1.161417″
29.75 mm	29.75	≈ 1.17126″
30 mm	30	≈ 1.181102″
30.25 mm	30.25	≈ 1.190945″
30.5 mm	30.5	≈ 1.200787″
30.75 mm	30.75	≈ 1.21063″
31 mm	31	≈ 1.220472″
31.25 mm	31.25	≈ 1.230315″
31.5 mm	31.5	≈ 1.240157″
31.75 mm	31.75	1.25″
32 mm	32	≈ 1.259843″
32.5 mm	32.5	≈ 1.279528″
33 mm	33	≈ 1.299213″
33.5 mm	33.5	≈ 1.318898″
34 mm	34	≈ 1.338583″
34.5 mm	34.5	≈ 1.358268″
35 mm	35	≈ 1.377953″
35.5 mm	35.5	≈ 1.397638″
36 mm	36	≈ 1.417323″
36.5 mm	36.5	≈ 1.437008″
37 mm	37	≈ 1.456693″
37.5 mm	37.5	≈ 1.476378″
38 mm	38	≈ 1.496063″
38.5 mm	38.5	≈ 1.515748″
39 mm	39	≈ 1.535433″
39.5 mm	39.5	≈ 1.555118″
40 mm	40	≈ 1.574803″
40.5 mm	40.5	≈ 1.594488″

Equal diameter, different designations

Different families can name the same cutting diameter. Letter E and a 1/4″ fractional drill both represent 6.35 mm. Nearby entries can also differ by small but real amounts; the chart preserves those differences.

For a tapped hole, start with the exact thread and its source-specific recommendation in the metric, UNC or UNF tapping table.

Sources & scope

Data edition 1.0. Values come from the reference sources below. SizeAxis is a selected reference catalogue; it does not certify manufactured dimensions or thread compatibility.

Read the measurement definitions and full coverage