Sheet Metal Gauge Converter

What Is Sheet Metal Gauge? Gauge is a traditional unit for sheet metal thickness, and a higher gauge number means thinner metal. The gauge system originated in the wire drawing trade in England and was later applied to sheet metal. Different gauge standards exist for different materials: steel, aluminum, and galvanized steel all use different gauge-to-thickness conversions. This is a major source of confusion: 18 gauge stainless steel is NOT the same thickness as 18 gauge aluminum.

Common Gauge Standards US Standard Gauge (USS): used for steel and galvanized steel. Manufacturer’s Standard Gauge (MSG): used for steel strip and sheet. American Wire Gauge (AWG) / Brown & Sharpe Gauge: for non-ferrous metals (aluminum, copper, brass). Birmingham Wire Gauge (BWG): for wire and tubing, different again.

Why Does Gauge Run Backwards? In wire drawing, metal is pulled through progressively smaller dies, and each pass counts as one “gauge.” More passes = thinner wire = higher gauge number. For sheet metal, the same convention was applied: thicker sheets had lower gauge numbers. This counterintuitive system persists because of industry tradition.

Manufacturer’s Standard Gauge to Thickness (Steel) This calculator uses MSG for plain steel, which is what steel sheet is actually sold to. US Standard Gauge is the older system and differs by a few thousandths: 18 gauge is 0.0500" under USS against 0.0478" under MSG.

7 gauge: 0.1793" (4.55 mm). 10 gauge: 0.1345" (3.42 mm). 12 gauge: 0.1046" (2.66 mm). 14 gauge: 0.0747" (1.90 mm). 16 gauge: 0.0598" (1.52 mm). 18 gauge: 0.0478" (1.21 mm). 20 gauge: 0.0359" (0.91 mm). 22 gauge: 0.0299" (0.76 mm). 24 gauge: 0.0239" (0.61 mm). 26 gauge: 0.0179" (0.45 mm). 28 gauge: 0.0149" (0.38 mm).

Stainless steel runs on its own gauge table, and the numbers are round fractions of an inch rather than the awkward decimals above: 16 gauge is exactly 1/16" (0.0625"), 18 gauge is 1/20" (0.0500"), 14 gauge is 5/64" (0.0781"). So 18 gauge stainless is about 5% thicker than 18 gauge plain steel. Order by decimal thickness, not by gauge number, whenever the two materials appear on the same drawing.

Common Applications by Gauge 3–7 gauge: heavy structural steel, armor plating, heavy machinery. 10–12 gauge: truck bodies, farm equipment, heavy ductwork. 14–16 gauge: HVAC ductwork, appliance frames, auto body panels. 18–20 gauge: light ductwork, enclosures, light auto body. 22–26 gauge: roofing panels, light HVAC, electronics enclosures. 28–30 gauge: foil, very thin sheet for art and light fabrication.

Weight Considerations Steel: 0.2904 lb/in³ (7.85 g/cm³). Aluminum: 0.0975 lb/in³ (2.70 g/cm³). Weight per sq ft = thickness (in) × 144 × density (lb/in³). 16 gauge steel sheet (0.0598"): ~2.50 lb/sq ft. 16 gauge aluminum (0.0508"): ~0.71 lb/sq ft. Note that aluminum wins twice over: it is both thinner at the same gauge number and about a third the density, so the sheet is roughly 3.5 times lighter rather than 3. Weight is critical for shipping costs, structural loads, and handling equipment ratings.

HVAC Ductwork Standards SMACNA (Sheet Metal and Air Conditioning Contractors’ National Association) specifies gauge by duct size and pressure class. Round duct up to 12": 26 gauge for low pressure, 24 gauge for medium, 22 gauge for high. Rectangular duct up to 12" dimension: 26 gauge for low pressure. Heavier gauge for fittings, elbows, and high-velocity systems.