Sheet Metal
Gauge Thickness Chart
Convert a gauge number to thickness in millimeters and inches by material. Full reference chart for steel, galvanized, stainless and aluminum.
Quick Convert
Full Gauge Chart — Standard Steel
| Gauge No. | mm | inch (″) |
|---|---|---|
| 3 ga | 6.073 | 0.2391 |
| 4 ga | 5.695 | 0.2242 |
| 5 ga | 5.314 | 0.2092 |
| 6 ga | 4.935 | 0.1943 |
| 7 ga | 4.554 | 0.1793 |
| 8 ga | 4.176 | 0.1644 |
| 9 ga | 3.797 | 0.1495 |
| 10 ga | 3.416 | 0.1345 |
| 11 ga | 3.038 | 0.1196 |
| 12 ga | 2.657 | 0.1046 |
| 13 ga | 2.278 | 0.0897 |
| 14 ga | 1.897 | 0.0747 |
| 15 ga | 1.709 | 0.0673 |
| 16 ga | 1.519 | 0.0598 |
| 17 ga | 1.367 | 0.0538 |
| 18 ga | 1.214 | 0.0478 |
| 19 ga | 1.062 | 0.0418 |
| 20 ga | 0.912 | 0.0359 |
| 21 ga | 0.836 | 0.0329 |
| 22 ga | 0.759 | 0.0299 |
| 23 ga | 0.683 | 0.0269 |
| 24 ga | 0.607 | 0.0239 |
| 25 ga | 0.531 | 0.0209 |
| 26 ga | 0.455 | 0.0179 |
| 28 ga | 0.378 | 0.0149 |
| 30 ga | 0.305 | 0.0120 |
Note: Gauge systems differ by material — the same gauge number gives a different thickness in steel and aluminum. Values are nominal; confirm supplier tolerance before ordering.
What is sheet metal gauge?
Gauge (ga) is a numbering system for sheet metal thickness. The rule runs backwards: the higher the gauge number, the THINNER the sheet (16 ga is thicker than 20 ga). The key point is that the gauge system differs by material — 16 gauge steel ≈ 1.52 mm while 16 gauge aluminum ≈ 1.29 mm. Always state the gauge together with its material.
Why does gauge thickness change by material?
For steel, the standard chart uses the Manufacturers' Standard Gauge (weight-based). Galvanized steel is slightly thicker at the same gauge because of the zinc coating. Stainless steel has its own gauge chart, and aluminum uses the AWG (Brown & Sharpe) system. The result: the same gauge number gives four different thicknesses across the four materials. In practice, ordering by mm/inch is the safest way to avoid mistakes; gauge is only a common shorthand. Sheet products are made to EN/ASTM standards with ± tolerance — for critical work, confirm supplier tolerance.
Frequently Asked Questions
How many mm is 16 gauge?+
In standard steel, 16 ga ≈ 1.52 mm (0.0598″). Galvanized steel ≈ 1.61 mm, stainless ≈ 1.59 mm, aluminum ≈ 1.29 mm. It depends on the material.
Is a higher gauge thicker or thinner?+
Thinner. As the gauge number rises the sheet gets thinner: 10 ga is thick, 24 ga is thin. The system runs backwards.
Why does gauge differ by material?+
Steel uses a weight-based standard gauge, aluminum uses AWG, and stainless has its own chart. The same number gives different thicknesses; always state the material.
Should I use mm instead of gauge?+
For international orders and critical work, yes — mm/inch is exact and material-independent. Gauge is only a common shop-floor shorthand.
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