When dealing with sheet metal, the term “gauge” is often used to describe its thickness. If you’re not familiar with the gauge system, you might find terms like “18 gauge steel” confusing. This guide will break down the gauge system and provide a handy sheet metal gauge chart to clarify the different thicknesses associated with each gauge number.
How are Sheet Metal Gauges Used?
Gauges are used to indicate the thickness of sheet metal, but they don’t align with standard or metric measurement systems. The gauge number itself doesn’t directly represent a specific thickness in inches or millimeters. Instead, a gauge conversion chart is needed to find the actual thickness. For instance, 18 gauge steel translates to 0.0478 inches or 1.214 millimeters, but the number “18” doesn’t correspond to any particular unit of measurement.
Different metals have their own gauge systems, so the same gauge number can mean different thicknesses for different materials. For example, 18 gauge steel is 0.0478 inches thick, while 18 gauge aluminum is 0.0403 inches thick. Because of these differences, it’s important to use a gauge chart to confirm that the metal meets the required thickness specifications.
History of the Gauge System
The gauge system, with its roots in the British wire industry, predates the widespread use of standard and metric measurement systems. Originally, it was developed to describe the diameter of metal wires. Over time, this system expanded to include the thickness of sheet metal as well.
Despite the availability of more precise measurement systems, the gauge system has remained a popular method for indicating the thickness of both wire and sheet metal. Its persistence is largely due to its deep historical roots and widespread use in metal fabrication.
Even though it doesn’t directly correspond to standard or metric units, the gauge system continues to be a practical and well-understood way to specify metal thickness, especially in industries where tradition plays a significant role.
Sheet Metal Gauge Charts
Use these sheet metal gauge charts to determine the metal gauge you require:
Mild Steel Gauge Chart
Aluminum Gauge Chart
Stainless Steel Gauge Chart
Galvanized Steel Gauge Chart
Brass Gauge Chart
Copper Gauge Chart
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
| 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
| 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
| 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
| 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
| 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 |
Summary
The gauge system, with its origins in the British wire industry, has a long-standing presence in metal fabrication. Initially used to measure the diameter of wires, it eventually expanded to include sheet metal thickness.
Despite the availability of standard and metric measurement systems, the gauge system remains widely used today. It offers a simple and accepted way to specify metal thickness, facilitating clear communication in the industry.
While gauge numbers don’t directly correlate to inches or millimeters, conversion charts are available to ensure accurate measurements. These charts help professionals maintain precision when working with different gauge sizes.
The gauge system endures in metal fabrication because of its historical roots, broad acceptance, and practical application. It continues to be a vital tool for those in manufacturing, construction, and related fields, ensuring clear communication and accurate measurements for successful projects.
FAQs
What is a sheet metal gauge?
A sheet metal gauge is a measurement system used to indicate the thickness of sheet metal. The gauge number inversely correlates with thickness—meaning a higher gauge number represents thinner metal. For steel, the gauge system is based on a weight of 41.82 pounds per square foot per inch of thickness.
Which is thicker 18 or 20 gauge sheet metal?
18-gauge sheet metal is thicker than 20-gauge sheet metal. As the gauge number increases, the thickness of the metal decreases.
How to calculate gauge thickness?
To calculate gauge thickness: A “mil” equals 1/1000th of an inch. Gauge is calculated as (100) x (mils), so 0.3 mils equals 30 gauge. To convert mils to microns, multiply mils by 25.4.
