Sheet Steel Gauge

When working with sheet metal, the term "gauge or gage" is often used, and is used to indicate the thickness of a metal sheet.

Gauge (Ga) is a unit of length for diameters originating in North America and belongs to the Browne & Sharpe measurement system. Originally used in the fields of medicine and jewelry, the larger the number, the smaller the diameter, and now it is also used to indicate thickness.

Ga is different from inches; there is no conversion formula. Even if the non-ferrous metal sheet and the steel sheet have the same Ga, the thickness is actually different.

You can find the conversion from Ga to Milimeters for sheet metal in the table below.

Gauge Number	Standard Steel	Galvanized Steel	Stainless Steel	Aluminum, Brass, Copper
3	6.073			5.827
4	5.095		5.954	5.189
5	5.314		5.555	4.62
6	4.935		5.159	4.115
7	4.554		4.763	3.665
8	4.176		4.191	3.264
9	3.797	3.891	3.967	2.906
10	3.416	3.51	3.571	2.588
11	3.038	3.132	3.175	2.304
12	2.657	2.753	2.779	2.052
13	2.278	2.372	2.38	1.829
14	1.897	1.994	1.984	1.628
15	1.709	1.803	1.786	1.45
16	1.519	1.613	1.588	1.29
17	1.367	1.461	1.427	1.151
18	1.214	1.311	1.27	1.024
19	1.062	1.158	1.11	0.912
20	0.912	1.006	0.953	0.813
21	0.836	0.93	0.874	0.724
22	0.759	0.853	0.792	0.643
23	0.683	0.777	0.714	0.574
24	0.607	0.701	0.635	0.536
25	0.531	0.627	0.556	0.455
26	0.455	0.551	0.475	0.404
27	0.417	0.513	0.437	0.361
28	0.378	0.475	0.396	0.32
29	0.343	0.437	0.358	0.287
30	0.305	0.399	0.318	0.254
31	0.267	0.361	0.277	0.226
32	0.246	0.34	0.259	0.203
33	0.229		0.239	0.18
34	0.208		0.218	0.16
35	0.191		0.198	0.142
36	0.17		0.178	0.127
37	0.163		0.168	0.113
38	0.17		0.157	0.101