A gauge number means a different thickness in each metal, and the numbers run backward: the higher the gauge, the thinner the sheet. In steel, 16 gauge is 0.0598 in (1.52 mm), 14 gauge 0.0747 in (1.90 mm) and 18 gauge 0.0478 in (1.21 mm). The same 16 gauge is 0.0635 in in galvanized steel, 0.0625 in in stainless and only 0.0508 in in aluminum.
Gauge chart
| Gauge | Steel, in · mm | Galvanized | Stainless | Aluminum |
|---|---|---|---|---|
| 7 | .1793 · 4.55 | – | .1875 · 4.76 | .1443 · 3.66 |
| 8 | .1644 · 4.18 | .1681 · 4.27 | .1719 · 4.37 | .1285 · 3.26 |
| 9 | .1495 · 3.80 | .1532 · 3.89 | .1562 · 3.97 | .1144 · 2.91 |
| 10 | .1345 · 3.42 | .1382 · 3.51 | .1406 · 3.57 | .1019 · 2.59 |
| 11 | .1196 · 3.04 | .1233 · 3.13 | .1250 · 3.17 | .0907 · 2.30 |
| 12 | .1046 · 2.66 | .1084 · 2.75 | .1094 · 2.78 | .0808 · 2.05 |
| 13 | .0897 · 2.28 | .0934 · 2.37 | .0938 · 2.38 | .0720 · 1.83 |
| 14 | .0747 · 1.90 | .0785 · 1.99 | .0781 · 1.98 | .0641 · 1.63 |
| 15 | .0673 · 1.71 | .0710 · 1.80 | .0703 · 1.79 | .0571 · 1.45 |
| 16 | .0598 · 1.52 | .0635 · 1.61 | .0625 · 1.59 | .0508 · 1.29 |
| 17 | .0538 · 1.37 | .0575 · 1.46 | .0563 · 1.43 | .0453 · 1.15 |
| 18 | .0478 · 1.21 | .0516 · 1.31 | .0500 · 1.27 | .0403 · 1.02 |
| 19 | .0418 · 1.06 | .0456 · 1.16 | .0437 · 1.11 | .0359 · 0.91 |
| 20 | .0359 · 0.91 | .0396 · 1.01 | .0375 · 0.95 | .0320 · 0.81 |
| 21 | .0329 · 0.84 | .0366 · 0.93 | .0344 · 0.87 | .0285 · 0.72 |
| 22 | .0299 · 0.76 | .0336 · 0.85 | .0312 · 0.79 | .0254 · 0.64 |
| 23 | .0269 · 0.68 | .0306 · 0.78 | .0281 · 0.71 | .0226 · 0.57 |
| 24 | .0239 · 0.61 | .0276 · 0.70 | .0250 · 0.64 | .0201 · 0.51 |
| 25 | .0209 · 0.53 | .0247 · 0.63 | .0219 · 0.56 | .0179 · 0.45 |
| 26 | .0179 · 0.45 | .0217 · 0.55 | .0187 · 0.48 | .0159 · 0.40 |
| 27 | .0164 · 0.42 | .0202 · 0.51 | .0172 · 0.44 | .0142 · 0.36 |
| 28 | .0149 · 0.38 | .0187 · 0.47 | .0156 · 0.40 | .0126 · 0.32 |
| 29 | .0135 · 0.34 | .0172 · 0.44 | .0141 · 0.36 | .0113 · 0.29 |
| 30 | .0120 · 0.30 | .0157 · 0.40 | .0125 · 0.32 | .0100 · 0.25 |
Inches · millimeters. Steel: the Manufacturers’ Standard Gauge, the 1893 law’s weight per square foot divided by 41.82. Galvanized: that weight plus 2.5 oz of zinc, the allowance the GalvInfo Center describes. Stainless: the law’s fraction thicknesses. Aluminum: the Brown & Sharpe gauge. All four columns match Metal Supermarkets’ published charts. Shaded: common gauges.
Why gauge numbers run backward
Sheet iron and steel were once sold by weight, and the gauge number was a shorthand for it. In 1893 Congress fixed “the only standard gauge for sheet and plate iron and steel” by weight per square foot (15 U.S.C. §206): 16 gauge is 2.5 lb per square foot, 10 gauge 5.625 lb, and each step up the scale is lighter, so thinner.
The thicknesses steel mills use today, the Manufacturers’ Standard Gauge, come from those weights: a square foot of steel 1 in thick weighs 41.82 lb, so 16 gauge is 2.5 ÷ 41.82 = 0.0598 in.
Galvanized, stainless and aluminum
- Galvanized steel runs thicker for the same gauge. The GalvInfo Center, the galvanizing industry’s information service, explains that the old galvanized sheet gauge was the steel thickness plus 0.0037 in for a thick hand-dipped zinc coat. The numbers stuck, though modern coatings such as G90 are much thinner.
- Stainless steel gauges follow the 1893 law’s round fractions, as steel suppliers list them: 16 gauge is 1/16 in (0.0625 in), 11 gauge 1/8 in.
- Aluminum uses the Brown & Sharpe gauge, the same scale as American Wire Gauge. Its sheets are thinner than steel at the same number: 16 gauge is 0.0508 in.
Because a gauge means a different thickness in each metal, and mills work to tolerances, give your supplier the decimal thickness you need, not only the gauge, and measure the sheet with calipers when it matters.
Weight of sheet steel
| Gauge | Steel, lb per sq ft | Galvanized, lb per sq ft | 4 × 8 ft sheet, steel |
|---|---|---|---|
| 10 | 5.625 | 5.781 | 180 lb |
| 11 | 5 | 5.156 | 160 lb |
| 12 | 4.375 | 4.531 | 140 lb |
| 14 | 3.125 | 3.281 | 100 lb |
| 16 | 2.5 | 2.656 | 80 lb |
| 18 | 2 | 2.156 | 64 lb |
| 20 | 1.5 | 1.656 | 48 lb |
| 22 | 1.25 | 1.406 | 40 lb |
| 24 | 1 | 1.156 | 32 lb |
| 26 | 0.75 | 0.906 | 24 lb |
Steel: 15 U.S.C. §206. Galvanized: plus the 2.5 oz (0.156 lb) of zinc per square foot that the galvanized gauge allowed for. A 4 × 8 ft sheet is 32 sq ft.
Questions people ask
Which is thicker, 14 gauge or 16 gauge?
14 gauge. In steel it is 0.0747 in, against 0.0598 in for 16 gauge: a lower gauge number is a thicker sheet.
How thick is 16 gauge steel in mm?
1.52 mm (0.0598 in).
How thick is 14 gauge steel?
0.0747 in, or 1.90 mm. In galvanized steel, 0.0785 in.
How thick is 10 gauge steel?
0.1345 in, or 3.42 mm. 11 gauge is 0.1196 in (3.04 mm), just under 1/8 in.
Is 26 or 29 gauge thicker?
26 gauge. In steel it is 0.0179 in against 0.0135 in for 29 gauge; galvanized, 0.0217 in against 0.0172 in.
Is 18 gauge thicker than 16 gauge?
No. 18 gauge steel is 0.0478 in, thinner than 16 gauge at 0.0598 in.
Sources
- 15 U.S.C. §206, Standard gauge for sheet and plate iron and steel (Act of March 3, 1893), via the Legal Information Institute
- GalvInfo Center, GalvInfoNote 1.1, Metallic-Coated Products and Specifications (galvanized sheet gauge and coating history)
- Metal Supermarkets, Sheet Metal Gauge Chart (mild steel, galvanized, stainless and aluminum, used to check our figures)
Checked October 12, 2026. Thicknesses rounded to 0.0001 in; millimeters at 25.4 mm to the inch. Aluminum thickness from the Brown & Sharpe formula: 0.005 × 92^((36 − gauge) ÷ 39) in.