A Guide to Sheet Metal Gauges and Conversions

9 November 2023 Edited 14 February 2024 2 min read

When it comes to working with sheet metal, understanding sheet metal gauges and their conversions is essential. In the UK, sheet metal is typically measured in SWG (Standard Wire Gauge), which is different from the measurements used in other parts of the world. This guide will help you decipher the intricacies of sheet metal gauges, convert SWG to millimeters (mm) and inches, and provide valuable insights into the world of sheet metal measurements.

Sheet Metal Gauges (SWG) Explained

What is SWG?

The Standard Wire Gauge, or SWG, is a British standard for measuring the thickness of various materials, including sheet metal. Unlike the American Wire Gauge (AWG) used for electrical wires, SWG measures thickness in reverse order, meaning a higher number indicates a thinner sheet.

SWG to Thickness

Understanding SWG is crucial for determining the thickness of sheet metal. The SWG scale ranges from 7/0 (the thickest) to 50 (the thinnest). Here's a conversion table for common SWG values and their approximate thickness in millimetres and inches:

SWG	Thickness (mm)	Thickness (inches)
7	4.6213 mm	0.1819 inches
10	3.2510 mm	0.1276 inches
12	2.6410 mm	0.1040 inches
14	2.0320 mm	0.0799 inches
16	1.6268 mm	0.0641 inches
18	1.2192 mm	0.0479 inches
20	0.9144 mm	0.0360 inches
22	0.7112 mm	0.0280 inches
24	0.5590 mm	0.0220 inches
26	0.4572 mm	0.0180 inches
28	0.3760 mm	0.0148 inches
30	0.3150 mm	0.0124 inches
32	0.2743 mm	0.0108 inches

Converting SWG to Metric (mm) and Imperial (inches)

Here's a quick reference for converting SWG measurements to millimeters (mm) and inches:

SWG to Millimeters (mm)

To convert SWG to millimetres, use the formula:

Thickness (mm) = 0.127 * (32 - SWG)

SWG to Inches

To convert SWG to inches, use the formula:

Thickness (inches) = 0.005 * (32 - SWG)

For example, if you have a sheet with an SWG of 18, you can calculate its thickness as follows:

Thickness (mm) = 0.127 * (32 - 18) = 1.778 mm

Thickness (inches) = 0.005 * (32 - 18) = 0.071 inches

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