Sheet metal is commonly described by gauge, which indicates the thickness of the particular piece of sheet metal. Since the gauge measurement system is independent of both the imperial and metric measurement systems (i.e., a gauge value of 18 is not equal to 18 inches or 18 centimeters), someone unfamiliar with it may find it difficult to understand.

The following guide provides an overview of the gauge measurement system. It describes how it is used, provides conversion charts for various materials, and discusses how to read them.

How Are Sheet Metal Gauges Used?

The gauge of a piece of sheet metal refers to its thickness. While this value is not provided in imperial or metric units, it can be converted to one or the other using a gauge conversion chart.

Sheet Metal Gauge Charts

Carbon 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

Download Steel Sheet Metal Gauge Chart

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

Download Stainless Steel Sheet Metal Gauge Chart

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

Download Aluminum Sheet Metal Gauge Chart

How to Read a Sheet Metal Gauge Chart

(Click to Expand)

Sheet metal gauge chart

The gauge system was originally developed in Britain to specify wire thickness in a time when there was no universal thickness unit. While some changes have been made and, at one point, a replacement was planned, the general concept of the system has remained the same. Today, it is used for both wire and sheet metal.

Sheet metal gauge conversion charts allow for the conversion of the gauge measurement into standard or metric units. However, there are a couple of things to keep in mind to ensure you achieve the proper converted value.

  1. The standard or metric equivalent of a gauge value depends on the metal. For example, 18-gauge sheet metal would be 0.040 inches thick if made from aluminum and 0.048 inches thick if made from stainless steel. That’s why it is important to ensure you use the right conversion chart for the given piece of sheet metal.
  2. The difference in metric or standard value from one gauge to the next is not equal. For example, 18-gauge sheet metal made from aluminum is 0.040 inches, 20-gauge sheet metal made from aluminum is 0.032 inches, and 16-gauge sheet metal made from aluminum is 0.050 inches. The difference in thickness between 18-gauge and 20-gauge is 0.008 inches, while the difference in thickness between 18-gauge and 16-gauge is 0.010 inches.

Custom Sheet Metal Fabrication Services at T/J Fabricators

Want to learn more about sheet metal gauges and how to decipher them for your next metal fabrication project? The experts at T/J Fabricators have got you covered!

Equipped with extensive experience providing custom sheet metal fabrication services to customers across a wide range of industries, we have what it takes to meet all of your sheet metal manufacturing needs. We can assist you in all aspects of fabrication, from CAD design and material selection to cutting and forming to welding and assembly to finishing and storage. Our engineers can work with a variety of metals, including aluminum, cold-rolled steel, hot-rolled steel, galvanized steel, and stainless steel.

To learn more about our precision sheet metal fabrication capabilities, contact us today. To get started on your next project, request a quote.


  1. Pam

    I have 26 sheets of 86 inch 20 hauge storm panels. Never used. Just trying to see how much they are worth. Heavy stuff.

  2. Luis Alejandro Camargo

    I bought an EASTWOOD (Sheet metal gage) it has two faces, each face cannot be interpreted, I don’t know if they are inches or mm, I bought this to measure the thickness or diameter of some wires, can you help me tell me where the inches are and the mm>?
    Thanks for your help, my E-mail is: camargo391@hotmail,com

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