Sheet Metal Gauge Chart

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Sheet Metal Gauge Chart: 18 Gauge Thickness in MM

In the sheet metal industry, "gauge" is a commonly-used term to refer to the thickness or thickness range of the material. But if you are not familiar with the gauge system, sometimes you may be confused about what a certain gauge is, for example 18 gauge steel. For simplicity, this blog will discuss the gauge system, and provide a handy sheet metal gauge chart for easy reference.

The gauge system is a standard system for measuring the thickness of sheet metals and is used to classify it. Each gauge is given a number with the lower the number the thicker the sheet and the higher the number the thinner the sheet. A thicker gauge steel is 18 gauge as opposed to 22 gauge, for instance. If accurate dimensions are needed, the thickness in mm could be useful in determining the material size if it is 18 gauge. Likewise, when calculating 18 gauge to mm, it offers a precise and clear guide for fabrication, engineering and design use.

For better understanding of gauge numbers and material thickness, a sheet metal gauge chart is provided in this blog. The table presents different gauge numbers and corresponding thickness measurements (inches and millimetres) which allow for easier comparisons and interpretation of different sheet metal gauges.

The gauge system and a sheet metal gauge chart will enable the reader to confidently make the right material thickness decisions for projects. In applications like manufacturing, construction, and metal fabrication, where precise measurements of sheet metal are essential for product quality and performance, the knowledge of the 18 gauge thickness (mm) is of particular importance.

How are Sheet Metal Gauges Used?

Gauges are used to define the thickness of sheet metal, are not standardized or related to standard or metric measurement systems. Gauge values are independent of each other and they are not in direct correlation with measurements. To determine the actual thickness of sheet metal in inches or millimetres, a gauge conversion chart is used.

The thickness values for each gauge are given here. It is for instance noted that 18 gauge in mm would be about 1.214 mm on the gauge conversion chart (0.0478 inches). Knowing how to convert 18 gauge to mm is important for precise measurements of various types of sheet metals. One should bear in mind that the gauge number does not directly correspond to the measurement.

Various gauges charts are used to measure various metals. For example, 18 gauge steel is 0.0478 inches thick as compared to 18 gauge aluminium, which is 0.0403 inches thick. The differences illustrate the need to check with a gauge chart to ensure that the correct size or dimensions have been obtained.

A gauge conversion chart can enable individuals to accurately determine the thickness of the sheet metal, irrespective of the gauge system or the kind of metal. This type of information is useful in sectors like manufacturing, construction, and metal fabrication, where accuracy in measurement is crucial.

Common Types of Sheet Metal to Consider

Picking the right sheet metal type is the first step in finding the right gauge and ensuring project success. Below are some of the more common sheet metals used in the industry, architecture and manufactured goods:

• Zinc-plated steel: Steel that is coated with zinc, providing it corrosion protection. Perfect for outdoor and/or moist environments (agriculture, solar mounting, automobile components, construction frames). 
• Stainless Steel: Stainless Steel is alloyed with at least 10.5% chromium to resist corrosion. Perfect for sanitary applications, medical devices, architectural uses, and food-grade applications.
• Aluminum: A lightweight, corrosion-resistant metal. Commonly used in aerospace, automotive, facades, food packaging and other manufactured goods.
• Brass: An alloy of copper and zinc, known for its attractive appearance and acoustic properties. Commonly used in musical instruments, architecture, plumbing, and electrical connectors.
• Copper: A pliable metal, with high conductive properties. Commonly used in electrical systems, plumbing, roofing and siding, industrial machinery and electronics.

Birmingham Gage (BG) Chart

Gauge	Thickness (in)	Thickness (mm)
0000000	0.6666	16.932
000000	0.6250	15.875
00000	0.5883	14.943
0000	0.5416	13.757
000	0.5000	12.700
00	0.4452	11.308
0	0.3964	10.069
1	0.3532	8.971
2	0.3147	7.993
3	0.2804	7.122
4	0.2500	6.350
5	0.2225	5.652
6	0.1981	5.032
7	0.1764	4.481
8	0.1570	3.988
9	0.1398	3.551
10	0.1250	3.175
11	0.1113	2.827
12	0.0991	2.517
13	0.0882	2.240
14	0.0785	1.994
15	0.0699	1.775
16	0.0625	1.588
17	0.0556	1.412
18	0.0495	1.257
19	0.0440	1.118
20	0.0392	0.996
21	0.0349	0.886
22	0.0312	0.792
23	0.0278	0.706
24	0.0247	0.627
25	0.0220	0.559
26	0.0196	0.498
27	0.0174	0.442
28	0.0156	0.396
29	0.0139	0.353
30	0.0123	0.312
31	0.0110	0.279
32	0.0098	0.249
33	0.0087	0.221
34	0.0077	0.196
35	0.0069	0.175
36	0.0061	0.155
37	0.0054	0.137
38	0.0048	0.122
39	0.0043	0.109
40	0.0038	0.097
41	0.0034	0.086
42	0.0030	0.076
43	0.0027	0.069
44	0.0024	0.061
45	0.0021	0.053
46	0.0019	0.048
47	0.0017	0.043
48	0.0016	0.041
49	0.0013	0.033
50	0.0012	0.030
51	0.0011	0.027
52	0.0010	0.024

Sheet Metal Gauge Thickness Chart

Gauge	Fraction (inches)	Stainless Steel inches (mm)	Galvanized Sheet inches (mm)	Steel inches (mm)	Aluminum inches (mm)
30	—	0.0125 (0.33)	0.0157 (0.40)	0.0120 (0.30)	0.0100 (0.25)
29	—	0.0141 (0.36)	0.0172 (0.44)	0.0135 (0.34)	0.0113 (0.29)
28	1/64	0.0156 (0.41)	0.0187 (0.47)	0.0149 (0.38)	0.0126 (0.32)
27	—	0.0172 (0.43)	0.0202 (0.51)	0.0164 (0.42)	0.0142 (0.36)
26	—	0.0187 (0.48)	0.0217 (0.55)	0.0179 (0.45)	0.0159 (0.40)
25	—	0.0219 (0.56)	0.0247 (0.63)	0.0209 (0.53)	0.0179 (0.46)
24	—	0.0250 (0.64)	0.0276 (0.70)	0.0239 (0.61)	0.0201 (0.51)
23	—	0.0281 (0.71)	0.0306 (0.78)	0.0269 (0.68)	0.0226 (0.58)
22	1/32	0.0312 (0.79)	0.0336 (0.85)	0.0299 (0.76)	0.0253 (0.64)
21	—	0.0344 (0.86)	0.0366 (0.93)	0.0329 (0.84)	0.0285 (0.71)
20	—	0.0375 (0.95)	0.0396 (1.01)	0.0359 (0.91)	0.0320 (0.81)
19	—	0.0437 (1.10)	0.0456 (1.16)	0.0418 (1.06)	0.0359 (0.91)
18	—	0.0500 (1.27)	0.0516 (1.31)	0.0478 (1.21)	0.0403 (1.02)
17	—	0.0562 (1.40)	0.0575 (1.46)	0.0538 (1.37)	0.0453 (1.10)
16	1/16	0.0625 (1.59)	0.0635 (1.61)	0.0598 (1.52)	0.0508 (1.29)
15	—	0.0703 (1.80)	0.0710 (1.80)	0.0673 (1.71)	0.0571 (1.40)
14	5/64	0.0781 (1.98)	0.0785 (1.99)	0.0747 (1.90)	0.0641 (1.63)
13	3/32	0.0940 (2.40)	0.0934 (2.37)	0.0897 (2.28)	0.0720 (1.80)
12	7/64	0.1094 (2.78)	0.1084 (2.75)	0.1046 (2.66)	0.0808 (2.05)
11	1/8	0.1250 (3.18)	0.1233 (3.13)	0.1196 (3.04)	0.0907 (2.30)
10	9/64	0.1406 (3.57)	0.1382 (3.51)	0.1345 (3.42)	0.1019 (2.59)
9	5/32	0.1563 (3.97)	0.1532 (3.89)	0.1495 (3.80)	0.1144 (2.91)
8	11/64	0.1719 (4.37)	0.1681 (4.27)	0.1644 (4.18)	0.1285 (3.26)
7	3/16	0.1875 (4.76)	0.1793 (4.55)	0.1443 (3.67)	—
6	13/64	0.2031	0.1943 (4.94)	0.1620 (4.10)	—
5	7/32	0.2187	0.2092 (5.31)	0.1819	—
4	15/64	0.2344	0.2242 (5.69)	0.2043	—
3	1/4	0.2500	0.2391 (6.07)	0.2294	—

History of the Gauge System

The gauge system is a traditional method used to measure the thickness of metals, with its roots tracing back to the British wire industry. Originally, it was designed to describe the diameter of drawn metal wires before standardised and metric measurement systems were widely adopted. Over time, this system became widely applied for both wire and sheet metal, providing a simple way to designate material thickness.

Although modern electrical cables are often measured by their cross-sectional area in square millimetres, the standard wire gauge (SWG) remains commonly used for sheet metal. When working with sheet metal, thickness can be accurately measured using tools like callipers or ultrasonic gauges, often with reference charts specific to the type of metal being used.

Sheet Metal Gauge Charts

Mild Steel Gauge Chart
Gauge Number	Inches	MM
7	.1793	4.554
8	.1644	4.175
9	.1495	3.797
10	.1345	3.416
11	.1196	3.038
12	.1046	2.656
14	.0747	1.897
16	.0598	1.518
18	.0478	1.214
20	.0359	.911
22	.0299	.759
24	.0239	.607
26	.0179	.454
28	.0149	.378

Aluminum Gauge Chart*
Gauge Number	Inches	MM
7	.1443	3.665
8	.1285	3.264
9	.1144	2.906
10	.1019	2.588
11	.09074	2.305
12	.08081	2.053
14	.06408	1.628
16	.05082	1.291
18	.04030	1.024
20	.03196	.812
22	.02535	.644
24	.02010	.511
26	.01594	.405
28	.01264	.321
30	.01003	.255

Stainless Steel Gauge Chart*
Gauge Number	Inches	MM
8	.17187	4.365
9	.15625	3.968
10	.14062	3.571
11	.125	3.175
12	.10937	2.778
14	.07812	1.984
16	.0625	1.587
18	.050	1.270
20	.0375	.9525
22	.03125	.7937
24	.025	.635
26	.01875	.476
28	.01562	.396
30	.0125	.3175

Galvanized Steel Gauge Chart*
Gauge Number	Inches	MM
8	.1681	4.269
9	.1532	3.891
10	.1382	3.510
11	.1233	3.1318
12	.1084	2.753
14	.0785	1.9939
16	.0635	1.6129
18	.0516	1.310
20	.0396	1.005
22	.0336	.853
24	.0276	.701
26	.0217	.551
28	.0187	.474
30	.0157	.398

Brass Gauge Chart*
Gauge Number	Inches	MM
7	.1443	3.665
8	.1285	3.264
9	.1144	2.906
10	.1019	2.588
11	.09074	2.305
12	.08081	2.053
14	.06408	1.628
16	.05082	1.291
18	.04030	1.024
20	.03196	.812
22	.02535	.644
24	.02010	.511
26	.01594	.405
28	.01264	.321
30	.01003	.255

Copper Gauge Chart*
Gauge Number	Inches	MM
7	.180	4.572
8	.165	4.191
9	.148	3.759
10	.134	3.404
11	.120	3.048
12	.109	2.769
14	.083	2.108
16	.065	1.651
18	.049	1.245
20	.035	.889
22	.028	.711
24	.022	.559
26	.018	.457
28	.014	.356
30	.012	.305

GAUGE CHART

GAUGE #	BRASS & ALUMINUM SHEETS		COLD & HOT ROLLED STEEL SHEETS		ALU., COPPER, BRASS, & STEEL TUBES COPPER SHEETS HOOP STEEL		STAINLESS STEEL SHEETS		GALVANIZED STEEL SHEETS
	INCHES	MM	INCHES	MM	INCHES	MM	INCHES	MM	INCHES	MM
7	1443	3.665	0.1793	4.554	0.180	4.572
8	0.1285	3.264	0.1644	4.175	0.165	4.191	0.17187	4.365	0.1681	4.269
9	0.1144	2.906	0.1495	3.797	0.148	3.759	0.15625	3.968	0.1532	3.891
10	0.1019	2.588	0.1345	3.416	0.134	3.404	0.14062	3.571	0.1382	3.510
11	0.09074	2.305	0.1196	3.038	0.120	3.048	0.125	3.175	0.1233	3.1318
12	0.08081	2.053	0.1046	2.656	0.109	2.769	0.10937	2.778	0.1084	2.753
14	0.06408	1.628	0.0747	1.897	0.083	2.108	0.07812	1.984	0.0785	1.9939
16	0.05082	1.291	0.0598	1.518	0.065	1.651	0.0625	1.587	0.0635	1.6129
18	0.04030	1.024	0.0478	1.214	0.049	1.245	0.050	1.270	0.0516	1.310
20	0.03196	0.812	0.0359	0.911	0.035	0.889	0.0375	0.9525	0.0396	1.005
22	0.02535	0.644	0.0299	0.759	0.028	0.711	0.03125	0.7937	0.0336	0.853
24	0.02010	0.511	0.0239	0.607	0.022	0.559	0.025	0.635	0.0276	0.701
26	0.01594	0.405	0.0179	0.454	0.018	0.457	0.01875	0.476	0.0217	0.551
28	0.01264	0.321	0.0149	0.378	0.014	0.356	0.01562	0.396	0.0187	0.474
30	0.01003	0.255	0.0120	0.305	0.012	0.305	0.0125	0.3175	0.0157	0.398

Standard Steel Gauge Chart

Gauge	Thickness (in)	Thickness (mm)	Weight (lb/ft²)	Weight (kg/m²)
3	0.2391	6.073	9.754	47.624
4	0.2242	5.695	9.146	44.656
5	0.2092	5.314	8.534	41.668
6	0.1943	4.935	7.927	38.701
7	0.1793	4.554	7.315	35.713
8	0.1644	4.176	6.707	32.745
9	0.1495	3.797	6.099	29.777
10	0.1345	3.416	5.487	26.790
11	0.1196	3.038	4.879	23.822
12	0.1046	2.657	4.267	20.834
13	0.0897	2.278	3.659	17.866
14	0.0747	1.897	3.047	14.879
15	0.0673	1.709	2.746	13.405
16	0.0598	1.519	2.440	11.911
17	0.0538	1.367	2.195	10.716
18	0.0478	1.214	1.950	9.521
19	0.0418	1.062	1.705	8.326
20	0.0359	0.912	1.465	7.151
21	0.0329	0.836	1.342	6.553
22	0.0299	0.759	1.220	5.955
23	0.0269	0.683	1.097	5.358
24	0.0239	0.607	0.975	4.760
25	0.0209	0.531	0.853	4.163
26	0.0179	0.455	0.730	3.565
27	0.0164	0.417	0.669	3.267
28	0.0149	0.378	0.608	2.968
29	0.0135	0.343	0.551	2.689
30	0.0120	0.305	0.490	2.390
31	0.0105	0.267	0.428	2.091
32	0.0097	0.246	0.396	1.932
33	0.0090	0.229	0.367	1.793
34	0.0082	0.208	0.335	1.633
35	0.0075	0.191	0.306	1.494
36	0.0067	0.170	0.273	1.335
37	0.0064	0.163	0.261	1.275
38	0.0060	0.152	0.245	1.195

Zinc Gauge Chart

Gauge	Thickness (in)	Thickness (mm)	Weight (lb/ft²)	Weight (kg/m²)
28	1.0000	25.400	37.152	181.392
27	0.5000	12.700	18.576	90.696
26	0.3750	9.525	13.932	68.022
25	0.2500	6.350	9.288	45.348
24	0.1250	3.175	4.644	22.674
23	0.1000	2.540	3.715	18.139
22	0.0900	2.286	3.344	16.325
21	0.0800	2.032	2.972	14.511
20	0.0700	1.778	2.601	12.697
19	0.0600	1.524	2.229	10.884
18	0.0550	1.397	2.043	9.977
17	0.0500	1.270	1.858	9.070
16	0.0450	1.143	1.672	8.163
15	0.0400	1.016	1.486	7.256
14	0.0360	0.914	1.337	6.530
13	0.0320	0.813	1.189	5.805
12	0.0280	0.711	1.040	5.079
11	0.0240	0.610	0.892	4.353
10	0.0200	0.508	0.743	3.628
9	0.0180	0.457	0.669	3.265
8	0.0160	0.406	0.594	2.902
7	0.0140	0.356	0.520	2.539
6	0.0120	0.305	0.446	2.177
5	0.0100	0.254	0.372	1.814
4	0.0080	0.203	0.297	1.451
3	0.0060	0.152	0.223	1.088
2	0.0040	0.102	0.149	0.726
1	0.0020	0.051	0.074	0.363

Conclusion

In conclusion, the gauge system has a long-standing history in the metal fabrication industry. Originating from the British wire industry, it was initially used to describe the diameter of metal wires being drawn. Over time, it expanded to include the thickness of sheet metal.

The gauge system remains prevalent today, even in the presence of standard and metric measurement systems. It provides a convenient and widely accepted method of designating the thickness of sheet metal, allowing for effective communication in the industry.

Although gauge values are independent of standard or metric measurements, conversion charts are available to determine the actual thickness in inches or millimeters. This ensures accuracy and consistency when working with sheet metal of varying gauges.

Overall, the gauge system's historical significance, widespread acceptance, and practicality have contributed to its continued use in metal fabrication. It serves as a valuable tool for professionals in industries such as manufacturing, construction, and metal fabrication, enabling effective communication and precise measurements for successful projects.

Amardeep Steel Centre

At Amardeep Steel, we stock and supply a wide range of carbon steel products , stainless steel products , alloy steel products, nickel alloy steel products , and special metals. Our inventory covers multiple shapes and forms such as sheets, plates, tubes, pipes, bars, and fittings, designed to meet diverse industrial applications.