Gauges are used to indicate the thickness of a sheet metal. Gauges are neither standard nor metric and values are independent of those measurement systems. The equivalent thicknesses differ for each gauge size standard, which were developed based on the weight of the sheet for a given material.
A sheet metal size chart provides information about various dimensions and sizes of sheet metal materials. Here is a common sheet metal gauge size chart that shows the various gauge numbers along with their corresponding thicknesses of sheet metal in both inches and millimeters are as follow in a table given below,
| Gauge | Thickness (in) | Thickness (mm) | Weight Per Area (lb/ft²) | Weight Per Area (kg/m²) |
| 3 | 0.2391 | 6.073 | 9.754 | 47.624 |
| 4 | 0.2242 | 5.695 | 9.146 | 44.656 |
| 5 | 0.2092 | 5.314 | 8.534 | 41.668 |
| 6 | 0.1943 | 4.935 | 7.927 | 38.701 |
| 7 | 0.1793 | 4.554 | 7.315 | 35.713 |
| 8 | 0.1644 | 4.176 | 6.707 | 32.745 |
| 9 | 0.1495 | 3.797 | 6.099 | 29.777 |
| 10 | 0.1345 | 3.416 | 5.487 | 26.790 |
| 11 | 0.1196 | 3.038 | 4.879 | 23.822 |
| 12 | 0.1046 | 2.657 | 4.267 | 20.834 |
| 13 | 0.0897 | 2.278 | 3.659 | 17.866 |
| 14 | 0.0747 | 1.897 | 3.047 | 14.879 |
| 15 | 0.0673 | 1.709 | 2.746 | 13.405 |
| 16 | 0.0598 | 1.519 | 2.440 | 11.911 |
| 17 | 0.0538 | 1.367 | 2.195 | 10.716 |
| 18 | 0.0478 | 1.214 | 1.950 | 9.521 |
| 19 | 0.0418 | 1.062 | 1.705 | 8.326 |
| 20 | 0.0359 | 1.062 | 1.465 | 7.151 |
| 21 | 0.0329 | 0.836 | 1.342 | 6.553 |
| 22 | 0.0299 | 0.759 | 1.220 | 5.955 |
| 23 | 0.0269 | 0.683 | 1.097 | 5.358 |
| 24 | 0.0239 | 0.607 | 0.975 | 4.760 |
| 25 | 0.0209 | 0.531 | 0.853 | 4.163 |
| 26 | 0.0179 | 0.455 | 0.730 | 3.565 |
| 27 | 0.0164 | 0.417 | 0.669 | 3.267 |
| 28 | 0.0149 | 0.378 | 0.608 | 2.968 |
| 29 | 0.0135 | 0.343 | 0.551 | 2.689 |
| 30 | 0.0120 | 0.305 | 0.490 | 2.390 |
| 31 | 0.0105 | 0.267 | 0.428 | 2.091 |
| 32 | 0.0097 | 0.246 | 0.396 | 1.932 |
| 33 | 0.0090 | 0.229 | 0.367 | 1.793 |
| 34 | 0.0082 | 0.208 | 0.335 | 1.633 |
| 35 | 0.0075 | 0.191 | 0.306 | 1.494 |
| 36 | 0.0067 | 0.170 | 0.273 | 1.335 |
| 37 | 0.0064 | 0.163 | 0.261 | 1.275 |
| 38 | 0.0060 | 0.152 | 0.245 | 1.195 |
Please note that sheet metal gauge sizes can vary slightly based on different standards (such as U.S. Standard, Brown & Sharpe, etc.), and so it’s important to confirm the specific standard being used for accuracy.
