Sheet metal gauge thickness chart
Nominal thickness by gauge number for the two metals shops mix most often. Higher gauge numbers are thinner metal; the same number means different thickness once you change material.
| Gauge | Carbon steel (MSG) | Aluminum (B&S) | ||
|---|---|---|---|---|
| in | mm | in | mm | |
| 7 | 0.1793 | 4.554 | 0.1443 | 3.665 |
| 8 | 0.1644 | 4.176 | 0.1285 | 3.264 |
| 9 | 0.1495 | 3.797 | 0.1144 | 2.906 |
| 10 | 0.1345 | 3.416 | 0.1019 | 2.588 |
| 11 | 0.1196 | 3.038 | 0.0907 | 2.304 |
| 12 | 0.1046 | 2.657 | 0.0808 | 2.052 |
| 13 | 0.0897 | 2.278 | 0.0720 | 1.829 |
| 14 | 0.0747 | 1.897 | 0.0641 | 1.628 |
| 15 | 0.0673 | 1.709 | 0.0571 | 1.450 |
| 16 | 0.0598 | 1.519 | 0.0508 | 1.290 |
| 17 | 0.0538 | 1.367 | 0.0453 | 1.151 |
| 18 | 0.0478 | 1.214 | 0.0403 | 1.024 |
| 19 | 0.0418 | 1.062 | 0.0359 | 0.912 |
| 20 | 0.0359 | 0.912 | 0.0320 | 0.813 |
| 21 | 0.0329 | 0.836 | 0.0285 | 0.724 |
| 22 | 0.0299 | 0.759 | 0.0253 | 0.643 |
| 23 | 0.0269 | 0.683 | 0.0226 | 0.574 |
| 24 | 0.0239 | 0.607 | 0.0201 | 0.511 |
| 25 | 0.0209 | 0.531 | 0.0179 | 0.455 |
| 26 | 0.0179 | 0.455 | 0.0159 | 0.404 |
| 27 | 0.0164 | 0.417 | 0.0142 | 0.361 |
| 28 | 0.0149 | 0.378 | 0.0126 | 0.320 |
Where these numbers come from
The steel column descends from the Manufacturers' Standard Gauge for sheet steel, originally defined as weight per unit area of rolled stock; thickness falls out of that definition. The aluminum column is Brown & Sharpe, whose geometric steps match the American Wire Gauge series — each gauge step changes thickness by the same ratio, unlike steel's irregular jumps.
To convert either column yourself, multiply inches by exactly 25.4 using the inches-to-mm converter.
Frequently asked questions
Why is "18 gauge" a different thickness for steel and aluminum?
They are two unrelated scales. Carbon-steel sheet follows the Manufacturers' Standard Gauge, which grew out of weight-per-area ratings for rolled iron. Aluminum (like copper and brass) uses the Brown & Sharpe gauge — the same progression as American Wire Gauge — so the same number lands about 15% thinner.
Does gauge include coating thickness?
The values here are bare/base metal. Hot-dip galvanized sheet adds zinc on both sides, typically 0.002"–0.007" depending on coating class (G90 adds roughly 0.003"). Order by decimal thickness plus coating spec when it matters.
How do I specify thickness so there is no confusion?
Put both the gauge and the decimal on the drawing or purchase order, e.g. '16 ga carbon steel (0.0598")' or '18 ga 5052 aluminum (0.0403")'. Gauge alone is ambiguous across metals, and mills roll to tolerances around the nominal anyway.
What about stainless steel?
Stainless sheet is commonly sold on its own gauge standard that runs slightly thicker than carbon steel at the same number (16 ga stainless ≈ 0.0625", close to 1/16"). Check your supplier's chart rather than assuming the steel column applies.
Steel per the Manufacturers' Standard Gauge for Sheet Steel as published by U.S. DOE/EIA conversion tables; aluminum per Brown & Sharpe (AWG) nonferrous gauge. Nominal values; mill tolerance applies.