Steel Gauge Thickness Guide: MM Charts & Conversion Tables

Steel gauge actually refers to the standard thickness of a sheet metal which follows an inversely proportional relationship between the gauge and thickness; in which the gauge increases when the sheet metal’s thickness falls and vice versa.

Steel or Sheet Metal

Steel is an alloy made up of different kinds of elements; but iron presents the greatest value compared to other components such as carbon. Sheet metal on the other hand is basically metal designed into thin quantities used for metalworking. The customary range gauge of a metal sheet is from a scale of 35 going down to 6. Nevertheless, in some situations sheet metal’s thickness can vary significantly which is then called foil or leaf. Thickness that is more than 6mm or 0.25 inches is called plates. These materials can be usually seen in construction works and are used for metalworking. Most of the bits and pieces we see and purchase are consist of such material and are develop for different kind of purposes. By using specific tools, this steel sheet metal can be cut, bent and form into creative work of arts such as those of car frames and aircraft wing extensions.

The Steel Gauge Chart         

Most people working with steel sheet metals consult to a particular chart for reference when it comes to gauge number and thickness. This chart is usually called the Steel Gauge Chart. It practically gives you the figures which indicate the sheet metal’s gauge and thickness in millimeter, inches and even fractional regular measurements. Here are the following statistics that shows the close association of the gauge and thickness.

Gauge No.	Thickness
	fraction	inch	mm
6	13/64	.2031	5.16
7	3/16	.1875	4.76
8	11/64	.1719	4.37
9	5/32	.1563	3.97
10	9/64	.1406	3.57
11	1/8	.1250	3.18
12	7/64	.1094	2.78
13	3/32	.0938	2.38
14	5/64	.0781	1.98
15	–	.0703	1.79
16	1/16	.0625	1.59
17	–	.0563	1.43
18	–	.0500	1.27
19	–	.0438	1.11
20	–	.0375	.953
21	–	.0344	.873
22	1/32	.0313	.794
23	–	.0218	.714
24	–	.0250	.635
25	–	.0219	.556
26	–	.0188	.478
27	–	.0172	.437
28	1/64	.0156	.396
29	–	.0141	.358
30	–	.0125	.318
31	–	.0109	.277
32	–	.0102	.259
33	–	.0094	.239
34	–	.0086	.218
35	–	.0078	.198

Chart link: http://www.offroaders.com/tech/steel-gauge-thickness.htm

It is clearly noted in the chart above that the connection between the gauge and thickness of sheet metals are opposite from each other.

Other Gauge Charts

	ALUMINUM		STEEL		Difference in (mm)
Gauge	inch	mm	inch	mm	mm
3	.2294	5.827	.2391	6.073	0.246
4	.2043	5.189	.2242	5.695	0.506
5	.1819	4.620	.2092	5.314	0.694
6	.1620	4.115	.1943	4.935	0.82
7	.1443	3.665	.1793	4.554	0.889
8	.1285	3.264	.1644	4.176	0.912
9	.1144	2.906	.1495	3.797	0.891
10	.1019	2.588	.1345	3.416	0.828
11	.0907	2.304	.1196	3.030	0.726
12	.0808	2.052	.1046	2.657	0.605
13	.0720	1.829	.0897	2.278	0.449
14	.0641	1.628	.0747	1.897	0.269
15	.0571	1.450	.0673	1.709	0.259
16	.0508	1.290	.0598	1.519	0.229
17	.0453	1.151	.0538	1.367	0.216
18	.0403	1.024	.0478	1.214	0.19
19	.0359	0.912	.0418	1.062	0.15
20	.0320	0.813	.0359	0.912	0.099
21	.0285	0.724	.0329	0.836	0.112
22	.0253	0.643	.0299	0.759	0.116
23	.0226	0.574	.0269	0.683	0.109
24	.0201	0.511	.0239	0.607	0.096
25	.0179	0.455	.0209	0.531	0.076
26	.0159	0.404	.0179	0.455	0.051
27	.0142	0.361	.0164	0.417	0.056
28	.0126	0.320	.0149	0.378	0.058
29	.0113	0.287	.0135	0.343	0.056
30	.0100	0.254	.0120	0.305	0.051
31	.0089	0.226	.0105	0.267	0.041
32	.0080	0.203	.0097	0.246	0.043
33	.0071	0.180	.0090	0.229	0.049
34	.0063	0.160	.0082	0.208	0.048
35	.0056	0.142	.0075	0.191	0.049

Chart link: http://www.offroaders.com/tech/steel-gauge-thickness.htm

The chart above represents the different values of gauge and thickness in ferrous scales (example is steel) and non-ferrous scales (example is aluminum). Aluminum when compared to steel shows the same relationship of the gauge and the thickness; however, the ferrous gauges have a higher thickness value contrary to the non-ferrous gauges. And when you go up sequentially, you’ll definitely observe the alteration between the figures. Initially it gradually increases and then quickly changes in a more progressive way. As you can see, the difference on its entirety varies from one point to another.

The Conversion Table

This conversion table will show us the exact values in decimal inches for every gauge for sheet steel, galvanized steel, stainless steel, aluminum and both strip and tubing. This is very essential when working or dealing with different kinds of steel and making numerous objects from it.

Gauge	US Standard Gauge	Sheet Steel	Galvanized Steel	Stainless Steel	Aluminium	Strip & Tubing
	(inches)	Gauge Decimal (inches)	Gauge Decimal (inches)	Gauge Decimal (inches)	Gauge Decimal (inches)	Gauge Decimal (inches)
35	0.0078	0.0075		0.0078	0.0056	0.005
34	0.0086	0.0082		0.0086	0.0063	0.007
33	0.0094	0.0090		0.0094	0.0071	0.008
32	0.0102	0.0097		0.0102	0.0080	0.009
31	0.0109	0.0105		0.0109	0.0089	0.010
30	0.0125	0.0120	0.016	0.0125	0.0100	0.012
29	0.0141	0.0135	0.017	0.0141	0.0113	0.013
28	0.0156	0.0149	0.019	0.0156	0.0126	0.014
27	0.0172	0.0164	0.020	0.0172	0.0142	0.016
26	0.0188	0.0179	0.022	0.0187	0.0159	0.018
25	0.0219	0.0209	0.025	0.0219	0.0179	0.020
24	0.0250	0.0239	0.028	0.0250	0.0201	0.022
23	0.0281	0.0269	0.031	0.0281	0.0226	0.025
22	0.0313	0.0299	0.034	0.0312	0.0253	0.028
21	0.0344	0.0329	0.037	0.0344	0.0285	0.032
20	0.0375	0.0359	0.040	0.0375	0.0320	0.035
19	0.0438	0.0418	0.046	0.0437	0.0359	0.042
18	0.0500	0.0478	0.052	0.0500	0.0403	0.049
17	0.0563	0.0538	0.058	0.0562	0.0453	0.058
16	0.0625	0.0598	0.064	0.0625	0.0508	0.065
15	0.0703	0.0673	0.071	0.0703	0.0571	0.072
14	0.0781	0.0747	0.079	0.0781	0.0641	0.083
13	0.0938	0.0897	0.093	0.0937	0.0720	0.095
12	0.1094	0.1046	0.108	0.1094	0.0808	0.109
11	0.1250	0.1196	0.123	0.1250	0.0907	0.120
10	0.1406	0.1345	0.138	0.1406	0.1019	0.134
9	0.1563	0.1495	0.153	0.1562	0.1144	0.148
8	0.1719	0.1644	0.168	0.1719	0.1285	0.165
7	0.1875	0.1793		0.1875	0.1443	0.180
6	0.2031	0.1943		0.2031	0.1620	0.203
5	0.2188	0.2092		0.2187	0.1819	0.220
4	0.2344	0.2242		0.2344	0.2043	0.238
3	0.2500	0.2391		0.2500	0.2294	0.259
2	0.2656			0.2656	0.2576	0.284
1	0.2813			0.2812	0.2893	0.300

Conversion Table link: http://www.engineeringtoolbox.com/gauge-sheet-d_915.html

At this time, it is important that one must remember that in dealing with such conversion process it is always best to study first the type of steel being used. You should first find out whether the steel utilized was galvanized or its plain stainless or sheet steel. Conversion differs and depends on what type of gauge system want to use. There are actually two gauge systems that can be use: the US Standard Gauge System and the MSG system or also known as the Manufacturer’s Standard Gauge system. The US standard gauge system usually uses the value from 2, 1, 0, 2/0, 3/0, 4/0, 5/0, 6/0 or 7/0. MSG’s largest thickness in sheet steel is 3. In galvanized steel it is 8 and for stainless steel it is 6/0. Next step for our conversion process is to determine the exact thickness of the material you’re using in its specific gauge. By multiplying 25.4 to your measurements you are actually converting the units into millimeters.