Sheet metal is sold by gauge, and the gauge number means a different thickness in different metals: 16 gauge steel is 0.0598 in, 16 gauge galvanized steel is 0.0635 in, and 16 gauge aluminium is 0.0508 in. The higher the number, the thinner the sheet. This chart gives the thickness in inches and millimetres for gauges 3 to 30 in plain steel, galvanized steel, stainless steel and aluminium, then what a 4 × 8 ft sheet of each weighs. Every figure is computed from the standard that defines the gauge, and the method is below so you can check it.
Sheet metal gauge thickness chart
| Gauge | Steel (in) | Steel (mm) | Galvanized (in) | Galvanized (mm) | Stainless (in) | Stainless (mm) | Aluminium (in) | Aluminium (mm) |
|---|---|---|---|---|---|---|---|---|
| 3 | 0.2391 | 6.07 | — | — | 0.2500 | 6.35 | 0.2294 | 5.83 |
| 4 | 0.2242 | 5.69 | — | — | 0.2344 | 5.95 | 0.2043 | 5.19 |
| 5 | 0.2092 | 5.31 | — | — | 0.2188 | 5.56 | 0.1819 | 4.62 |
| 6 | 0.1943 | 4.93 | — | — | 0.2031 | 5.16 | 0.1620 | 4.12 |
| 7 | 0.1793 | 4.56 | — | — | 0.1875 | 4.76 | 0.1443 | 3.66 |
| 8 | 0.1644 | 4.18 | 0.1681 | 4.27 | 0.1719 | 4.37 | 0.1285 | 3.26 |
| 9 | 0.1495 | 3.80 | 0.1532 | 3.89 | 0.1562 | 3.97 | 0.1144 | 2.91 |
| 10 | 0.1345 | 3.42 | 0.1382 | 3.51 | 0.1406 | 3.57 | 0.1019 | 2.59 |
| 11 | 0.1196 | 3.04 | 0.1233 | 3.13 | 0.1250 | 3.17 | 0.0907 | 2.30 |
| 12 | 0.1046 | 2.66 | 0.1084 | 2.75 | 0.1094 | 2.78 | 0.0808 | 2.05 |
| 13 | 0.0897 | 2.28 | 0.0934 | 2.37 | 0.0938 | 2.38 | 0.0720 | 1.83 |
| 14 | 0.0747 | 1.90 | 0.0785 | 1.99 | 0.0781 | 1.98 | 0.0641 | 1.63 |
| 15 | 0.0673 | 1.71 | 0.0710 | 1.80 | 0.0703 | 1.79 | 0.0571 | 1.45 |
| 16 | 0.0598 | 1.52 | 0.0635 | 1.61 | 0.0625 | 1.59 | 0.0508 | 1.29 |
| 17 | 0.0538 | 1.37 | 0.0575 | 1.46 | 0.0563 | 1.43 | 0.0453 | 1.15 |
| 18 | 0.0478 | 1.21 | 0.0516 | 1.31 | 0.0500 | 1.27 | 0.0403 | 1.02 |
| 19 | 0.0418 | 1.06 | 0.0456 | 1.16 | 0.0437 | 1.11 | 0.0359 | 0.91 |
| 20 | 0.0359 | 0.91 | 0.0396 | 1.01 | 0.0375 | 0.95 | 0.0320 | 0.81 |
| 21 | 0.0329 | 0.84 | 0.0366 | 0.93 | 0.0344 | 0.87 | 0.0285 | 0.72 |
| 22 | 0.0299 | 0.76 | 0.0336 | 0.85 | 0.0312 | 0.79 | 0.0253 | 0.64 |
| 23 | 0.0269 | 0.68 | 0.0306 | 0.78 | 0.0281 | 0.71 | 0.0226 | 0.57 |
| 24 | 0.0239 | 0.61 | 0.0276 | 0.70 | 0.0250 | 0.64 | 0.0201 | 0.51 |
| 25 | 0.0209 | 0.53 | 0.0247 | 0.63 | 0.0219 | 0.56 | 0.0179 | 0.45 |
| 26 | 0.0179 | 0.46 | 0.0217 | 0.55 | 0.0187 | 0.48 | 0.0159 | 0.40 |
| 27 | 0.0164 | 0.42 | 0.0202 | 0.51 | 0.0172 | 0.44 | 0.0142 | 0.36 |
| 28 | 0.0149 | 0.38 | 0.0187 | 0.47 | 0.0156 | 0.40 | 0.0126 | 0.32 |
| 29 | 0.0135 | 0.34 | 0.0172 | 0.44 | 0.0141 | 0.36 | 0.0113 | 0.29 |
| 30 | 0.0120 | 0.30 | 0.0157 | 0.40 | 0.0125 | 0.32 | 0.0100 | 0.25 |
Sheet metal weight by gauge
| Gauge | Steel (lb/ft²) | Steel 4 × 8 sheet (lb) | Galvanized 4 × 8 (lb) | Stainless 4 × 8 (lb) | Aluminium 4 × 8 (lb) |
|---|---|---|---|---|---|
| 3 | 10.000 | 320 | — | 333 | 103 |
| 4 | 9.375 | 300 | — | 312 | 92 |
| 5 | 8.750 | 280 | — | 291 | 82 |
| 6 | 8.125 | 260 | — | 271 | 73 |
| 7 | 7.500 | 240 | — | 250 | 65 |
| 8 | 6.875 | 220 | 225 | 229 | 58 |
| 9 | 6.250 | 200 | 205 | 208 | 51 |
| 10 | 5.625 | 180 | 185 | 187 | 46 |
| 11 | 5.000 | 160 | 165 | 166 | 41 |
| 12 | 4.375 | 140 | 145 | 146 | 36 |
| 13 | 3.750 | 120 | 125 | 125 | 32 |
| 14 | 3.125 | 100 | 105 | 104 | 29 |
| 15 | 2.812 | 90 | 95 | 94 | 26 |
| 16 | 2.500 | 80 | 85 | 83 | 23 |
| 17 | 2.250 | 72 | 77 | 75 | 20 |
| 18 | 2.000 | 64 | 69 | 67 | 18 |
| 19 | 1.750 | 56 | 61 | 58 | 16 |
| 20 | 1.500 | 48 | 53 | 50 | 14 |
| 21 | 1.375 | 44 | 49 | 46 | 13 |
| 22 | 1.250 | 40 | 45 | 42 | 11 |
| 23 | 1.125 | 36 | 41 | 37 | 10 |
| 24 | 1.000 | 32 | 37 | 33 | 9 |
| 25 | 0.875 | 28 | 33 | 29 | 8 |
| 26 | 0.750 | 24 | 29 | 25 | 7 |
| 27 | 0.688 | 22 | 27 | 23 | 6 |
| 28 | 0.625 | 20 | 25 | 21 | 6 |
| 29 | 0.562 | 18 | 23 | 19 | 5 |
| 30 | 0.500 | 16 | 21 | 17 | 5 |
Why one gauge number means four thicknesses
The gauge system for iron and steel sheet comes from a federal law. The Act of March 3, 1893 (now 15 U.S.C. 206) set the “only standard gauge for sheet and plate iron and steel” in the United States, and it defined each gauge by weight per square foot, not thickness: 16 gauge is 40 ounces per square foot, 10 gauge is 90 ounces, and so on. The thicknesses printed in the Act assumed wrought iron, at 40 lb per square foot per inch of thickness. Steel is a little heavier, so the steel industry later published the Manufacturers’ Standard Gauge, which keeps the Act’s weights and divides by 41.82 lb per square foot per inch. That is why 16 gauge steel is 0.0598 in rather than the Act’s 1/16 in (0.0625 in). The law also allows a variation of 2.5% either way (15 U.S.C. 208).
Galvanized sheet is listed with the weight of its zinc coating included, 2.5 ounces per square foot added to the base weight, so each galvanized gauge is slightly thicker than the same plain steel gauge. Stainless sheet is often listed by the Act’s original thicknesses, though some suppliers use the steel figures, so check the decimal thickness on the quote. Aluminium, copper and brass sheet use a different system altogether, the Brown & Sharpe gauge, which is the same formula as American Wire Gauge. When precision matters, specify the thickness in inches or millimetres instead of a gauge; many metal suppliers now do.
Steel framing: gauge and mils
Cold-formed steel studs and track are now specified by their minimum base-metal thickness in mils (thousandths of an inch) rather than gauge. The steel framing industry’s usual equivalents are 18 mils for 25 gauge, 30 or 33 mils for 20 gauge, 43 mils for 18 gauge, 54 mils for 16 gauge, 68 mils for 14 gauge and 97 mils for 12 gauge. The mil figure is a minimum, so it sits a little under the nominal gauge thickness in the chart above (for example 54 mils = 0.054 in against 0.0598 in for 16 gauge).
Worked examples
Weight of a 4 × 8 sheet of 16 gauge steel. The Act gives 40 oz = 2.5 lb per square foot, so 32 sq ft × 2.5 = 80 lb. Its thickness is 2.5 ÷ 41.82 = 0.0598 in (1.52 mm).
Is 11 gauge 1/8 in? In the 1893 Act, yes: 11 gauge is listed as 1/8 in (0.125 in). As steel sheet by the Manufacturers’ Standard Gauge it is 0.1196 in, about 3.04 mm. Plate thicker than about 3/16 in is normally ordered by its thickness, not a gauge.
Tips
- Measure with calipers or a micrometer, away from the sheet edge. A plain gauge wheel reads only the system it was made for.
- Painted or coated sheet measures thicker than the bare metal; roofing panels are often listed by gauge and by the base steel thickness.
- For bending, the inside bend radius and the minimum flange both scale with thickness; check the press brake or brake maker’s chart. The bend allowance calculator works out the flat length for a bend.
- For welding, thin gauges (20 and above) burn through easily; lower amperage and stitch welds help.
Frequently asked questions
How thick is 16 gauge steel?
0.0598 in (1.52 mm) for plain steel sheet and 0.0635 in (1.61 mm) galvanized. Stainless listed by the US Standard Gauge is 0.0625 in (1.59 mm), and 16 gauge aluminium is 0.0508 in (1.29 mm).
Is a higher gauge thicker or thinner?
Thinner. Gauge numbers began in the wire trade, where a higher number meant more passes through the drawing dies and so a thinner wire; sheet gauges kept the same direction.
How thick is 18 gauge steel in mm?
1.21 mm (0.0478 in) for plain steel; galvanized 18 gauge is 1.31 mm.
What gauge is 1/8 inch steel?
11 gauge in the US Standard Gauge (exactly 1/8 in); as steel sheet, 11 gauge is 0.1196 in, so 1/8 in plate is usually ordered as 1/8 in.
Does aluminium use the same gauge as steel?
No. Aluminium sheet uses the Brown & Sharpe (American Wire) gauge, so the same number is thinner: 16 gauge aluminium is 0.0508 in against 0.0598 in for steel.
Sources
- 15 U.S.C. 206, Standard gauge for sheet and plate iron and steel (Act of March 3, 1893, 27 Stat. 746): gauge numbers and weight per square foot; 15 U.S.C. 208: 2.5% variation. Federal law, public domain.
- Manufacturers’ Standard Gauge for steel sheet (thickness = USSG weight ÷ 41.82 lb/ft² per inch) and the galvanized 2.5 oz/ft² coating allowance, as published by steel producers and suppliers.
- ASTM B258, Standard Specification for Standard Nominal Diameters and Cross-Sectional Areas of AWG Sizes of Solid Round Wires: the Brown & Sharpe / AWG formula d = 0.005 × 92^((36 − n)/39) in.
- Cold-formed steel framing mil designations as published by the Steel Stud Manufacturers Association (SSMA) and Steel Framing Industry Association.
Last reviewed: 24 October 2026. Numbers in the tables are our arithmetic from the sources listed; code sections are summarised, not quoted. How we check our work: methodology and corrections. Spotted an error? Please let us know.