Gauge (Ga.) is often used to specify the wire diameter. Originally, gauge referred to the number of wire draws used in the process. The first draw was called No. 1, the second No. 2, the third No. 3, and so on until the last draw, i.e. the thinnest wire. This is why thicker wire has a lower gauge than finer wire, for example, 9 gauge is thicker than 14 gauge because it is drawn less often than 14 gauge. Later, gauge was also used to refer to the thickness of a metal sheet. Next, Wanzhi Steel will take you to learn more.

Origin of Gauge

The use of “Gauge” to denote thickness dates back to the beginning of the industrial revolution in the United States. At that time, people who produce wire needed a way to quantify the product they were selling. The simplest method, of course, was the weight method. But if a buyer simply offered to buy 15 pounds of steel wire without specifying the diameter of the wire, it could cause a lot of trouble. So, the wire makers would quote the diameter based on the number of wire pulls they had performed, and that is how gauge originated.

Comparison Table of Different Units

When non-ferrous sheet metal and steel are of a certain Ga. number, the thicknesses are different. For example, 21 Ga. corresponds to a standard steel thickness of 0.0329inches (0.84mm); it corresponds to a galvanized steel thickness of 0.0366 inches (0.93mm), and it corresponds to an aluminum thickness of 0.028 inches (0.71mm). The following is the unit comparison table for your reference.

Gauge (Ga.)	Standard Steel Thickness (Inch)	Galvanized Steel Thickness (Inch)	Aluminum Thickness (Inch)	Standard Steel Thickness (mm)	Galvanized Steel Thickness (mm)	Aluminum Thickness (mm)
3	0.2391		0.2294	6.07314		5.82676
4	0.2242		0.2043	5.69468		5.18922
5	0.2092		0.1819	5.31368		4.62026
6	0.1943		0.162	4.93522		4.1148
7	0.1793		0.1443	4.55422		3.66522
8	0.1644		0.1285	4.17576		3.2639
9	0.1495	0.1532	0.1144	3.7973	3.89128	2.90576
10	0.1345	0.1382	0.1019	3.4163	3.51028	2.58826
11	0.1196	0.1233	0.0907	3.03784	3.13182	2.30378
12	0.1046	0.1084	0.0808	2.65684	2.75336	2.05232
13	0.0897	0.0934	0.072	2.27838	2.37236	1.8288
14	0.0747	0.0785	0.0641	1.89738	1.9939	1.62814
15	0.0673	0.071	0.0571	1.70942	1.8034	1.45034
16	0.0598	0.0635	0.0508	1.51892	1.6129	1.29032
17	0.0538	0.0575	0.0453	1.36652	1.4605	1.15062
18	0.0478	0.0516	0.0403	1.21412	1.31064	1.02362
19	0.0418	0.0456	0.0359	1.06172	1.15824	0.91186
20	0.0359	0.0396	0.032	0.91186	1.00584	0.8128
21	0.0329	0.0366	0.0285	0.83566	0.92964	0.7239
22	0.0299	0.0336	0.0253	0.75946	0.85344	0.64262
23	0.0269	0.0306	0.0226	0.68326	0.77724	0.57404
24	0.0239	0.0276	0.0201	0.60706	0.7004	0.51054
25	0.0209	0.0247	0.0179	0.53086	0.62738	0.45466
26	0.0179	0.0217	0.0159	0.45466	0.55118	0.40386
27	0.0164	0.0202	0.0142	0.41656	0.51308	0.36068
28	0.0149	0.0187	0.0126	0.37846	0.47498	0.32004
29	0.0135	0.0172	0.0113	0.3429	0.43688	0.28702
30	0.012	0.0157	0.01	0.3048	0.39878	0.254
31	0.0105	0.0142	0.0089	0.2667	0.36068	0.22606
32	0.0097	0.0134	0.008	0.24638	0.34036	0.2032
33	0.009		0.0071	0.2286		0.18034
34	0.0082		0.0063	0.20828		0.16002
35	0.0075		0.0056	0.1905		0.14224
36	0.0067			0.17018