Drill Size Chart

D: Drill size: the diameter across the body, measured over the two lands at the start of the flutes
θ: Point angle: usually 118° for general-purpose drills, 135° for harder metals

A twist drill from the side. The size is the diameter of the body; the shank can be the same or smaller (reduced shank drills).

Number drills

Drill	Inches	mm	Nearest metric drill
#1	0.2280	5.79	5.8 mm
#2	0.2210	5.61	5.6 mm
#3	0.2130	5.41	5.4 mm
#4	0.2090	5.31	5.3 mm
#5	0.2055	5.22	5.2 mm
#6	0.2040	5.18	5.2 mm
#7	0.2010	5.11	5.1 mm
#8	0.1990	5.05	5.1 mm
#9	0.1960	4.98	5.0 mm
#10	0.1935	4.91	4.9 mm
#11	0.1910	4.85	4.9 mm
#12	0.1890	4.80	4.8 mm
#13	0.1850	4.70	4.7 mm
#14	0.1820	4.62	4.6 mm
#15	0.1800	4.57	4.6 mm
#16	0.1770	4.50	4.5 mm
#17	0.1730	4.39	4.4 mm
#18	0.1695	4.31	4.3 mm
#19	0.1660	4.22	4.2 mm
#20	0.1610	4.09	4.1 mm
#21	0.1590	4.04	4.0 mm
#22	0.1570	3.99	4.0 mm
#23	0.1540	3.91	3.9 mm
#24	0.1520	3.86	3.9 mm
#25	0.1495	3.80	3.8 mm
#26	0.1470	3.73	3.7 mm
#27	0.1440	3.66	3.7 mm
#28	0.1405	3.57	3.6 mm
#29	0.1360	3.45	3.5 mm
#30	0.1285	3.26	3.3 mm
#31	0.1200	3.05	3.0 mm
#32	0.1160	2.95	2.9 mm
#33	0.1130	2.87	2.9 mm
#34	0.1110	2.82	2.8 mm
#35	0.1100	2.79	2.8 mm
#36	0.1065	2.71	2.7 mm
#37	0.1040	2.64	2.6 mm
#38	0.1015	2.58	2.6 mm
#39	0.0995	2.53	2.5 mm
#40	0.0980	2.49	2.5 mm
#41	0.0960	2.44	2.4 mm
#42	0.0935	2.37	2.4 mm
#43	0.0890	2.26	2.3 mm
#44	0.0860	2.18	2.2 mm
#45	0.0820	2.08	2.1 mm
#46	0.0810	2.06	2.1 mm
#47	0.0785	1.99	2.0 mm
#48	0.0760	1.93	1.9 mm
#49	0.0730	1.85	1.9 mm
#50	0.0700	1.78	1.8 mm
#51	0.0670	1.70	1.7 mm
#52	0.0635	1.61	1.6 mm
#53	0.0595	1.51	1.5 mm
#54	0.0550	1.40	1.4 mm
#55	0.0520	1.32	1.3 mm
#56	0.0465	1.18	1.2 mm

Number drills fill the gaps between the fractional sizes, so there's a drill for every common tap and clearance hole. #7 (0.201 in) is the 1/4-20 tap drill.

Letter drills

Drill	Inches	mm	Nearest metric drill
A	0.2340	5.94	5.9 mm
B	0.2380	6.05	6.0 mm
C	0.2420	6.15	6.1 mm
D	0.2460	6.25	6.2 mm
E	0.2500	6.35	6.3 mm
F	0.2570	6.53	6.5 mm
G	0.2610	6.63	6.6 mm
H	0.2660	6.76	6.8 mm
I	0.2720	6.91	6.9 mm
J	0.2770	7.04	7.0 mm
K	0.2810	7.14	7.1 mm
L	0.2900	7.37	7.4 mm
M	0.2950	7.49	7.5 mm
N	0.3020	7.67	7.7 mm
O	0.3160	8.03	8.0 mm
P	0.3230	8.20	8.2 mm
Q	0.3320	8.43	8.4 mm
R	0.3390	8.61	8.6 mm
S	0.3480	8.84	8.8 mm
T	0.3580	9.09	9.1 mm
U	0.3680	9.35	9.3 mm
V	0.3770	9.58	9.6 mm
W	0.3860	9.80	9.8 mm
X	0.3970	10.08	10.1 mm
Y	0.4040	10.26	10.3 mm
Z	0.4130	10.49	10.5 mm

Letter drills carry on above #1. E is the same as 1/4 in.

Fractional drills

Drill	Inches	mm	Nearest metric drill
1/64 in	0.0156	0.40	Smaller than 1 mm
1/32 in	0.0313	0.79	Smaller than 1 mm
3/64 in	0.0469	1.19	1.2 mm
1/16 in	0.0625	1.59	1.6 mm
5/64 in	0.0781	1.98	2.0 mm
3/32 in	0.0938	2.38	2.4 mm
7/64 in	0.1094	2.78	2.8 mm
1/8 in	0.1250	3.17	3.2 mm
9/64 in	0.1406	3.57	3.6 mm
5/32 in	0.1563	3.97	4.0 mm
11/64 in	0.1719	4.37	4.4 mm
3/16 in	0.1875	4.76	4.8 mm
13/64 in	0.2031	5.16	5.2 mm
7/32 in	0.2188	5.56	5.6 mm
15/64 in	0.2344	5.95	6.0 mm
1/4 in	0.2500	6.35	6.3 mm
17/64 in	0.2656	6.75	6.7 mm
9/32 in	0.2813	7.14	7.1 mm
19/64 in	0.2969	7.54	7.5 mm
5/16 in	0.3125	7.94	7.9 mm
21/64 in	0.3281	8.33	8.3 mm
11/32 in	0.3438	8.73	8.7 mm
23/64 in	0.3594	9.13	9.1 mm
3/8 in	0.3750	9.52	9.5 mm
25/64 in	0.3906	9.92	9.9 mm
13/32 in	0.4063	10.32	10.3 mm
27/64 in	0.4219	10.72	10.7 mm
7/16 in	0.4375	11.11	11.1 mm
29/64 in	0.4531	11.51	11.5 mm
15/32 in	0.4688	11.91	11.9 mm
31/64 in	0.4844	12.30	12.3 mm
1/2 in	0.5000	12.70	12.7 mm
33/64 in	0.5156	13.10	13.0 mm
17/32 in	0.5313	13.49	13.5 mm
35/64 in	0.5469	13.89	14 mm
9/16 in	0.5625	14.29	14.5 mm
37/64 in	0.5781	14.68	14.5 mm
19/32 in	0.5938	15.08	15 mm
39/64 in	0.6094	15.48	15.5 mm
5/8 in	0.6250	15.88	16 mm
41/64 in	0.6406	16.27	16.5 mm
21/32 in	0.6563	16.67	16.5 mm
43/64 in	0.6719	17.07	17 mm
11/16 in	0.6875	17.46	17.5 mm
45/64 in	0.7031	17.86	18 mm
23/32 in	0.7188	18.26	18.5 mm
47/64 in	0.7344	18.65	18.5 mm
3/4 in	0.7500	19.05	19 mm
49/64 in	0.7656	19.45	19.5 mm
25/32 in	0.7813	19.84	20 mm
51/64 in	0.7969	20.24	20 mm
13/16 in	0.8125	20.64	20.5 mm
53/64 in	0.8281	21.03	21 mm
27/32 in	0.8438	21.43	21.5 mm
55/64 in	0.8594	21.83	22 mm
7/8 in	0.8750	22.22	22 mm
57/64 in	0.8906	22.62	22.5 mm
29/32 in	0.9063	23.02	23 mm
59/64 in	0.9219	23.42	23.5 mm
15/16 in	0.9375	23.81	24 mm
61/64 in	0.9531	24.21	24 mm
31/32 in	0.9688	24.61	24.5 mm
63/64 in	0.9844	25.00	25 mm
1 in	1.0000	25.40	25.5 mm

Fractional drills come in 1/64 in steps (0.0156 in, about 0.4 mm).

Metric drills

Drill	Inches	Nearest inch drill
1.0 mm	0.0394	#56 (0.0465 in)
1.5 mm	0.0591	#53 (0.0595 in)
2.0 mm	0.0787	#47 (0.0785 in)
2.5 mm	0.0984	#40 (0.098 in)
3.0 mm	0.1181	#31 (0.12 in)
3.5 mm	0.1378	#29 (0.136 in)
4.0 mm	0.1575	#22 (0.157 in)
4.5 mm	0.1772	#16 (0.177 in)
5.0 mm	0.1969	#9 (0.196 in)
5.5 mm	0.2165	7/32 in
6.0 mm	0.2362	B (0.238 in)
6.5 mm	0.2559	F (0.257 in)
7.0 mm	0.2756	J (0.277 in)
7.5 mm	0.2953	M (0.295 in)
8.0 mm	0.3150	O (0.316 in)
8.5 mm	0.3346	Q (0.332 in)
9.0 mm	0.3543	T (0.358 in)
9.5 mm	0.3740	3/8 in
10.0 mm	0.3937	25/64 in
10.5 mm	0.4134	Z (0.413 in)
11.0 mm	0.4331	7/16 in
11.5 mm	0.4528	29/64 in
12.0 mm	0.4724	15/32 in
12.5 mm	0.4921	31/64 in
13.0 mm	0.5118	33/64 in
13.5 mm	0.5315	17/32 in
14 mm	0.5512	35/64 in
14.5 mm	0.5709	37/64 in
15 mm	0.5906	19/32 in
15.5 mm	0.6102	39/64 in
16 mm	0.6299	5/8 in
16.5 mm	0.6496	21/32 in
17 mm	0.6693	43/64 in
17.5 mm	0.6890	11/16 in
18 mm	0.7087	45/64 in
18.5 mm	0.7283	47/64 in
19 mm	0.7480	3/4 in
19.5 mm	0.7677	49/64 in
20 mm	0.7874	25/32 in
20.5 mm	0.8071	13/16 in
21 mm	0.8268	53/64 in
21.5 mm	0.8465	27/32 in
22 mm	0.8661	55/64 in
22.5 mm	0.8858	57/64 in
23 mm	0.9055	29/32 in
23.5 mm	0.9252	59/64 in
24 mm	0.9449	15/16 in
24.5 mm	0.9646	31/32 in
25 mm	0.9843	63/64 in

Metric jobber drills also come in 0.1 mm steps up to 13 mm (5.1, 5.2 mm…); the tap drill calculator lists them all. The nearest inch drill can be a fraction, number or letter.

Use the Tap Drill Size Calculator

About this chart

The size of every number, letter and fractional drill in inches and millimetres, and metric drills in inches. Each has the nearest drill in the other system, for when you have one set but the plan uses the other. Choose a set above the chart.

Number drills go down in size as the number goes up: #1 is 0.228 in, #56 is 0.0465 in. Letter drills go up: A is 0.234 in, just above #1, and Z is 0.413 in. For the drill to use before tapping a thread, use the tap drill calculator.

How it's worked out: mm = inches × 25.4 exactly. Number and letter drill sizes are the ANSI/ASME B94.11 series; fractional drills are n/64 in. The nearest drill is the closest size in the other set (metric jobber drills in 0.1 mm steps to 13 mm and 0.5 mm steps above; inch fractional, number and letter drills).

Drills cut very slightly oversize, typically a few hundredths of a millimetre, more if the point is ground off-centre. For an exact size, drill undersize and ream.

Last checked 31 October 2026 · Last rev. 31 October 2026 · 311d

Drill Size Chart

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Number drills

Letter drills

Fractional drills

Metric drills

About this chart

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