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Metal Sheet Thickness Standards SWG Inches Millimeters Explained

2026-01-09

Selecting the appropriate metal sheet thickness can be challenging, especially when navigating between different measurement standards such as SWG (Standard Wire Gauge), inches, and millimeters. This comprehensive guide provides essential conversion tables and industry insights to streamline material selection for engineering and fabrication projects.

Understanding Metal Sheet Specifications

Modern metal fabrication utilizes various thickness measurement systems depending on material type and regional standards. The most common include:

SWG (Standard Wire Gauge): Primarily used in the UK for non-ferrous metals
Inches: Common in North American manufacturing
Millimeters: The international metric standard
ZG (Zinc Gauge): A specialized system for zinc sheets

Standard Metal Sheet Dimensions

Industrial metal sheets are available in standardized sizes, though custom dimensions are frequently produced for specific applications. Common maximum dimensions include:

Material	Maximum Dimensions	Maximum Thickness
Copper/Brass	3000mm x 1000mm (8' x 4')	3mm
Zinc	3000mm x 1100mm (8' x 4')	1.5mm
Corten Steel	2500mm x 1250mm	Varies
Tin	2000mm x 1000mm	Varies
Aluminum/Stainless Steel	2500mm x 1250mm	Varies
Bronze	2000mm x 1000mm	Varies

Zinc Sheet Thickness: The ZG Standard

Zinc sheets follow a unique measurement system called ZG (Zinc Gauge), which operates inversely to SWG - higher gauge numbers indicate thicker sheets. This system, while less common in general metalworking, remains important for zinc-specific applications.

ZG to Millimeter Conversion

ZG	Approx. Thickness (mm)
6 ZG	0.3
7 ZG	0.35
8 ZG	0.40
9 ZG	0.45
10 ZG	0.5
11 ZG	0.6
12 ZG	0.7
13 ZG	0.8
14 ZG	0.9
15 ZG	1.0
16 ZG	1.1
17 ZG	1.2
18 ZG	1.4
19 ZG	1.5
20 ZG	1.8
21 ZG	2.0
22 ZG	2.3
23 ZG	2.5
24 ZG	3.0

Comprehensive Thickness Conversion Table

The following table provides conversions between SWG, inches, and millimeters for precise material specification:

SWG	Inches	Millimeters	SWG	Inches	Millimeters
7/0	0.500	12.70	23	0.024	0.61
6/0	0.464	11.79	24	0.022	0.56
5/0	0.432	10.97	25	0.0020	0.51
4/0	0.400	10.16	26	0.018	0.46
3/0	0.372	9.45	27	0.016	0.42
2/0	0.348	8.84	28	0.015	0.38
1/0	0.324	8.24	29	0.014	0.35
1	0.300	7.62	30	0.012	0.32
2	0.276	7.01	31	0.012	0.30
3	0.252	6.40	32	0.011	0.27
4	0.232	5.89	33	0.010	0.25
5	0.212	5.39	34	0.009	0.23
6	0.192	4.88	35	0.008	0.21
7	0.176	4.47	36	0.008	0.19
8	0.160	4.06	37	0.007	0.17
9	0.144	3.66	38	0.006	0.15
10	0.128	3.25	39	0.005	0.13
11	0.116	2.95	40	0.005	0.12
12	0.104	2.64	41	0.004	0.11
13	0.092	2.34	42	0.004	0.10
14	0.080	2.03	43	0.004	0.09
15	0.072	1.83	44	0.003	0.08
16	0.064	1.63	45	0.003	0.07
17	0.056	1.42	46	0.002	0.06
18	0.048	1.22	47	0.002	0.05
19	0.040	1.02	48	0.002	0.04
20	0.036	0.91	49	0.001	0.03
21	0.032	0.81	50	0.001	0.03
22	0.028	0.71

Industry Recommendations

The metal fabrication industry increasingly recommends using metric measurements (millimeters) for thickness specifications to avoid confusion between different gauge systems. Metric measurements provide unambiguous communication across international projects and supply chains.

Modern manufacturing equipment, particularly CNC machines and laser cutters, typically operate using metric measurements, making millimeter specifications more practical for digital fabrication processes.

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