Gauge is the most common way to call out sheet thickness and the easiest to get wrong, because the same gauge number means a different thickness in carbon steel, galvanized steel, stainless and aluminum. Here is the chart, what each gauge is used for, and how to call thickness out so there is no argument later.
Want a design-for-fabrication review on your drawing? Call 601.892.5017 or email collin.t@fabtekindustries.com — send the model or drawing and our engineers will mark it up.
- Carbon steel: 7 ga = 0.1793″ (4.55 mm), 10 ga = 0.1345″ (3.42 mm), 11 ga = 0.1196″, 12 ga = 0.1046″ (2.66 mm), 14 ga = 0.0747″ (1.90 mm), 16 ga = 0.0598″ (1.52 mm).
- The same gauge differs by material. Galvanized steel runs about 0.0037″ thicker than bare steel; stainless uses its own table; aluminum uses a different gauge system entirely and is usually called out in decimals.
- Call out decimal thickness, not just gauge — e.g., “0.1046″ (12 ga) ASTM A1008 CS” — so the material, the table and the tolerance are unambiguous.
The gauge chart
| Gauge | Carbon steel | Galvanized steel | Stainless steel | Aluminum |
|---|---|---|---|---|
| 7 | 0.1793″ / 4.55 mm | — | 0.1875″ / 4.76 mm | 0.1443″ / 3.67 mm |
| 8 | 0.1644″ / 4.18 mm | 0.1681″ / 4.27 mm | 0.1719″ / 4.37 mm | 0.1285″ / 3.26 mm |
| 10 | 0.1345″ / 3.42 mm | 0.1382″ / 3.51 mm | 0.1406″ / 3.57 mm | 0.1019″ / 2.59 mm |
| 11 | 0.1196″ / 3.04 mm | 0.1233″ / 3.13 mm | 0.1250″ / 3.18 mm | 0.0907″ / 2.30 mm |
| 12 | 0.1046″ / 2.66 mm | 0.1084″ / 2.75 mm | 0.1094″ / 2.78 mm | 0.0808″ / 2.05 mm |
| 14 | 0.0747″ / 1.90 mm | 0.0785″ / 1.99 mm | 0.0781″ / 1.98 mm | 0.0641″ / 1.63 mm |
| 16 | 0.0598″ / 1.52 mm | 0.0635″ / 1.61 mm | 0.0625″ / 1.59 mm | 0.0508″ / 1.29 mm |
| 18 | 0.0478″ / 1.21 mm | 0.0516″ / 1.31 mm | 0.0500″ / 1.27 mm | 0.0403″ / 1.02 mm |
| 20 | 0.0359″ / 0.91 mm | 0.0396″ / 1.01 mm | 0.0375″ / 0.95 mm | 0.0320″ / 0.81 mm |
| 22 | 0.0299″ / 0.76 mm | 0.0336″ / 0.85 mm | 0.0312″ / 0.79 mm | 0.0253″ / 0.64 mm |
| 24 | 0.0239″ / 0.61 mm | 0.0276″ / 0.70 mm | 0.0250″ / 0.64 mm | 0.0201″ / 0.51 mm |
Nominal thicknesses: Manufacturers’ Standard Gauge for carbon steel, galvanized sheet gauge (coated thickness), common stainless sheet gauge, and Brown & Sharpe (AWG) for aluminum. Mill thickness tolerances (ASTM A568 for carbon sheet, A924 for coated sheet, A480 for stainless, B209 for aluminum) apply on top of the nominal value.
Why the same gauge differs by material
Gauge numbers are historical: they began as a measure of weight per square foot, not a measure of thickness, and different industries kept their own tables. Carbon steel follows the Manufacturers’ Standard Gauge. Galvanized sheet is the base steel plus its zinc coating, so each gauge runs about 0.0037″ thicker. Stainless is sold on its own, slightly thicker table (and increasingly by decimal). Aluminum uses the Brown & Sharpe wire gauge, which is much thinner at the same number — 12 ga aluminum is 0.0808″, not 0.1046″ — which is why aluminum is almost always ordered by decimal: 0.063, 0.080, 0.090, 0.125. Above about 3/16″, material is generally treated as plate and called out by fraction or decimal rather than gauge.
What each gauge is used for
| Gauge (steel) | Typical uses in electrical and industrial fabrication |
|---|---|
| 7 ga | Light base plates, heavy brackets, walk-in enclosure bases and floors, equipment pads |
| 10–11 ga | Walk-in and pad-mount enclosure panels, heavy doors, tank covers, switchgear frames, skid decking |
| 12 ga | Outdoor NEMA 3R panels and doors, switchgear and control-cabinet bodies, bus duct housings |
| 14 ga | Indoor and outdoor cabinets, control enclosures, doors, internal barriers, mounting panels |
| 16 ga | Indoor enclosures, covers, wireways, internal panels and brackets |
| 18–20 ga | Light covers, filler panels, ductwork, trim |
Gauge choices for a specific product depend on size, stiffening, rating and the customer’s standard. Outdoor walk-in enclosures are covered in detail in What Gauge Steel for a NEMA 3R Walk-In Enclosure?
How to write it
“Material: 0.1046″ (12 ga) cold-rolled steel, ASTM A1008 CS Type B” or “0.0785″ (14 ga) galvanized steel, ASTM A653 CS, G90” or “0.125″ aluminum, 5052-H32, ASTM B209.” Give the decimal first, the gauge in parentheses as a convenience, the material specification and, for coated sheet, the coating weight. If the drawing is going to a fabricator who will unfold it, the model thickness must match the decimal on the drawing — a 3D model built at 0.105″ for a 0.1046″ sheet throws every flat pattern off slightly (see Part 3).
How FabTek handles it
FabTek stocks and processes carbon, galvanized and galvanneal sheet, stainless and aluminum from thin gauge through plate, cut on the fiber lasers and formed on ten press brakes and the MEGAbend panel folder. Engineering confirms the decimal thickness and material spec on every drawing during DFM review, and heat numbers from the mill test report are carried to the part. Choosing between cold-rolled, galvanneal and galvanized sheet is Part 8.
Frequently asked questions
How thick is 10 gauge steel?
10 gauge carbon steel is 0.1345 inch, or about 3.42 mm. 10 gauge galvanized steel is about 0.1382 inch, 10 gauge stainless is about 0.1406 inch, and 10 gauge aluminum is only 0.1019 inch.
How thick is 14 gauge steel in mm?
14 gauge carbon steel is 0.0747 inch, or about 1.90 mm. 14 gauge galvanized is about 0.0785 inch (1.99 mm) and 14 gauge stainless about 0.0781 inch (1.98 mm).
Why is aluminum gauge different from steel gauge?
Aluminum uses the Brown and Sharpe (AWG) gauge system, while carbon steel uses the Manufacturers' Standard Gauge, so the same number is much thinner in aluminum. That is why aluminum sheet is usually ordered by decimal thickness such as 0.063, 0.080 or 0.125 inch.
What gauge is 1/8 inch steel?
1/8 inch is 0.125 inch, which falls between 11 gauge (0.1196 inch) and 10 gauge (0.1345 inch) in carbon steel. In stainless sheet, 11 gauge is nominally 0.125 inch. It is clearer to call out 0.125 inch directly.
