Drill Bit Size Chart

Number drills #1–#80, letter drills A–Z, and common metric sizes — with decimal inch and millimetre equivalents. Use as a quick workshop reference.

Number Drill Sizes (#1–#80)

Drill #	Decimal (in)	mm
#1	0.2280	5.791
#2	0.2210	5.613
#3	0.2130	5.410
#4	0.2090	5.309
#5	0.2055	5.220
#6	0.2040	5.182
#7	0.2010	5.105
#8	0.1990	5.055
#9	0.1960	4.978
#10	0.1935	4.915
#11	0.1910	4.851
#12	0.1890	4.801
#13	0.1850	4.699
#14	0.1820	4.623
#15	0.1800	4.572
#16	0.1770	4.496
#17	0.1730	4.394
#18	0.1695	4.305
#19	0.1660	4.216
#20	0.1610	4.089
#21	0.1590	4.039
#22	0.1570	3.988
#23	0.1540	3.912
#24	0.1520	3.861
#25	0.1495	3.797
#26	0.1470	3.734
#27	0.1440	3.658
#28	0.1405	3.569
#29	0.1360	3.454
#30	0.1285	3.264
#31	0.1200	3.048
#32	0.1160	2.946
#33	0.1130	2.870
#34	0.1110	2.819
#35	0.1100	2.794
#36	0.1065	2.705
#37	0.1040	2.642
#38	0.1015	2.578
#39	0.0995	2.527
#40	0.0980	2.489
#41	0.0960	2.438
#42	0.0935	2.375
#43	0.0890	2.261
#44	0.0860	2.184
#45	0.0820	2.083
#46	0.0810	2.057
#47	0.0785	1.994
#48	0.0760	1.930
#49	0.0730	1.854
#50	0.0700	1.778
#51	0.0670	1.702
#52	0.0635	1.613
#53	0.0595	1.511
#54	0.0550	1.397
#55	0.0520	1.321
#56	0.0465	1.181
#57	0.0430	1.092
#58	0.0420	1.067
#59	0.0410	1.041
#60	0.0400	1.016
#61	0.0390	0.991
#62	0.0380	0.965
#63	0.0370	0.940
#64	0.0360	0.914
#65	0.0350	0.889
#66	0.0330	0.838
#67	0.0320	0.813
#68	0.0310	0.787
#69	0.0292	0.742
#70	0.0280	0.711
#71	0.0260	0.660
#72	0.0250	0.635
#73	0.0240	0.610
#74	0.0225	0.572
#75	0.0210	0.533
#76	0.0200	0.508
#77	0.0180	0.457
#78	0.0160	0.406
#79	0.0145	0.368
#80	0.0135	0.343

Letter Drill Sizes (A–Z)

Letter	Decimal (in)	mm
A	0.2340	5.944
B	0.2380	6.045
C	0.2420	6.147
D	0.2460	6.248
E	0.2500	6.350
F	0.2570	6.528
G	0.2610	6.629
H	0.2660	6.756
I	0.2720	6.909
J	0.2770	7.036
K	0.2810	7.137
L	0.2900	7.366
M	0.2950	7.493
N	0.3020	7.671
O	0.3160	8.026
P	0.3230	8.204
Q	0.3320	8.433
R	0.3390	8.611
S	0.3480	8.839
T	0.3580	9.093
U	0.3680	9.347
V	0.3770	9.576
W	0.3860	9.804
X	0.3970	10.082
Y	0.4040	10.262
Z	0.4130	10.490

Common Metric Drill Sizes

Size (mm)	Decimal (in)	Common use
1.0	0.0394	—
1.5	0.0591	—
2.0	0.0787	—
2.5	0.0984	M3 tap drill
3.0	0.1181	—
3.3	0.1299	M4 tap drill
3.5	0.1378	—
4.0	0.1575	—
4.2	0.1654	M5 tap drill
5.0	0.1969	M6 tap drill
5.5	0.2165	—
6.0	0.2362	—
6.5	0.2559	—
6.8	0.2677	M8 tap drill
7.0	0.2756	—
8.0	0.3150	—
8.5	0.3346	M10 tap drill
9.0	0.3543	—
10.0	0.3937	—
10.2	0.4016	M12 tap drill
11.0	0.4331	—
12.0	0.4724	—
13.0	0.5118	—
14.0	0.5512	M16 tap drill

How to Use This Reference

Number drills decrease in size as the number increases: #1 is the largest (0.228 in / 5.79 mm), #80 is the smallest (0.0135 in / 0.34 mm). Letter drills run A (smallest, 0.234 in) through Z (largest, 0.413 in). These systems are common in the US and are frequently used for tap drilling imperial threads.

Metric drills are used directly by nominal diameter and are the standard outside the US. For tap drilling metric threads, refer to the Tap Drill Chart for recommended sizes.

Related References

Tap Drill Chart Find the correct drill size before tapping metric, UNC, and UNF threads. View chart → Fraction to Decimal Chart 1/64 through 63/64 inch fractions with decimal and mm equivalents. View chart → Bolt Grade Chart Metric and SAE bolt grades with tensile strength and head markings. View chart →

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