Drill Bit Size Chart: Inch, Metric, Number & Letter Sizes

Choosing the right drill bit size is essential for accurate holes, clean machining, proper tapping, and reliable fastening. This drill bit size chart provides a practical reference for common metric drill bits, fractional inch drill bits, number drill bits, and letter drill bits used in metalworking, woodworking, construction, maintenance, and industrial production.

Whether you are drilling pilot holes, preparing holes for tapping, or selecting bits for CNC machining, the following drill bit size tables help you quickly compare diameters in inches and millimeters.

Metric Drill Bit Size Chart

Metric drill bits are widely used in industrial manufacturing, machinery repair, automotive work, and general engineering applications.

Fractional Inch Drill Bit Size Chart

Fractional inch drill bits are commonly used in North America for general drilling, maintenance, fabrication, and construction work.

Number Drill Bit Size Chart

Number drill bits are often used for precision drilling, tapping preparation, electronics, aerospace, and metalworking applications.

Number Size	Decimal inch	Diameter mm
#80	0.0135	0.343
#79	0.0145	0.368
#78	0.016	0.406
#77	0.018	0.457
#76	0.02	0.508
#75	0.021	0.533
#74	0.0225	0.572
#73	0.024	0.61
#72	0.025	0.635
#71	0.026	0.66
#70	0.028	0.711
#69	0.0292	0.742
#68	0.031	0.787
#67	0.032	0.813
#66	0.033	0.838
#65	0.035	0.889
#64	0.036	0.914
#63	0.037	0.94
#62	0.038	0.965
#61	0.039	0.991
#60	0.04	1.016
#59	0.041	1.041
#58	0.042	1.067
#57	0.043	1.092
#56	0.0465	1.181
#55	0.052	1.321
#54	0.055	1.397
#53	0.0595	1.511
#52	0.0635	1.613
#51	0.067	1.702
#50	0.07	1.778
#49	0.073	1.854
#48	0.076	1.93
#47	0.0785	1.994
#46	0.081	2.057
#45	0.082	2.083
#44	0.086	2.184
#43	0.089	2.261
#42	0.0935	2.375
#41	0.096	2.438
#40	0.098	2.489
#39	0.0995	2.527
#38	0.1015	2.578
#37	0.104	2.642
#36	0.1065	2.705
#35	0.11	2.794
#34	0.111	2.819
#33	0.113	2.87
#32	0.116	2.946
#31	0.12	3.048
#30	0.1285	3.264
#29	0.136	3.454
#28	0.1405	3.569
#27	0.144	3.658
#26	0.147	3.734
#25	0.1495	3.797
#24	0.152	3.861
#23	0.154	3.912
#22	0.157	3.988
#21	0.159	4.039
#20	0.161	4.089
#19	0.166	4.216
#18	0.1695	4.305
#17	0.173	4.394
#16	0.177	4.496
#15	0.18	4.572
#14	0.182	4.623
#13	0.185	4.699
#12	0.189	4.801
#11	0.191	4.851
#10	0.1935	4.915
#9	0.196	4.978
#8	0.199	5.055
#7	0.201	5.105
#6	0.204	Drill Bit Coatings Guide HSS vs Carbide Drill Bits: Which One Is Better for Industrial Applications? Latest Blog Drill Bit Coatings Guide Learn the main types of drill bit coatings, including black oxide, TiN, TiAlN, TiCN, cobalt, carbide-tipped and diamond drill bits. June. 08, 2026 Drill Bit Size Chart: Inch, Metric, Number & Letter Sizes Complete drill bit size chart with metric, fractional inch, number, and letter drill sizes. May. 29, 2026 We use cookies We use cookies and other tracking technologies to improve your browsing experience on our website, to show you personalized content and targeted ads, to analyze our website traffic, and to understand where our visitors are coming from. I agree I decline