When working with sheet metal, the thickness of the material is commonly referred to as "gauge". If you are unfamiliar with the gauge system, the term 14 gauge may not make any sense to you. To help, this article will explain the gauge system and I have also included a metal gauge chart both online and as a PDF that you can download and save to your phone, computer or tablet.
Where Did The Gauge System Come From?
The gauge system is said to have originated from the British wire industry before the standard and metric measurement systems were widely adopted. During that time, gauges were used to identify the diameter of the wire being drawn. Since then, "gauge" has remained the unit of measurement to describe wire diameter and sheet metal thickness.
Sheet Metal Gauge Use
Gauges are used to measure the thickness of sheet metal and they are neither imperial and the values are independent of those measurement systems. A gauge conversion chart can be used to determine the actual thickness of sheet metal in inches or millimeters. For example, 14 gauge steel measures .0747" thick (or 1.897 mm). However, 14 gauge aluminum is .06408" thick (or 1.628 mm). Because of these varying thicknesses, it is always recommended to use a gauge thickness chart when working on a project and ordering material to ensure you are getting the required dimensions.
Sheet Metal Gauge Charts
Use the following charts to find the metal gauge you need for your project.
Or download the PDF chart here: 
| 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 Guage 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 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 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 |
Sheet Metal Thickness Gauge Reference