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Sheet Metal Gauge Table (mm and inches)

Nominal thickness by gauge number for carbon steel, stainless steel and aluminum. Each column names its standard, because the same gauge number is not the same thickness in different materials.

Nominal values. Inches rounded to 4 decimals; mm = inches × 25.4, rounded to 3 decimals.

Which standard is which

Carbon steel (MSG). The Manufacturers’ Standard Gage is the scale commonly used in industry for steel sheet. The official NBS documents we reviewed do not define it, so its values were checked against two independently published tables, which agree for every gauge shown.

Stainless steel (U.S. Standard Gage). This is the scale fixed by U.S. law in 1893 for sheet and plate iron and steel (15 U.S.C. § 206), defined by weight per square foot. The values published by stainless suppliers match this scale. Some sources apply the MSG scale to stainless, so confirm with your supplier.

Aluminum (Brown & Sharpe = AWG). The NBS lists the American Wire Gage (Brown & Sharpe) for copper, brass and aluminum sheet. Thickness in inches is 0.005 × 92^(36−n)/39, where n is the gauge number.

Before you use the table

• Values are nominal: actual thickness varies within the material and supplier tolerances.
• Galvanized sheet has its own gauge, different from uncoated steel, and is not in this table.
• For design, purchasing and simulation, always specify thickness in mm or inches, not just the gauge.

Sources

Primary sources (official documents)

• 15 U.S. Code § 206, “Standard gauge for sheet and plate iron and steel” (Act of March 3, 1893)
• National Bureau of Standards, Letter Circular LC-24, “Standard Thicknesses of Sheet Metal” (rev. 1925)
• National Bureau of Standards, Circular 391, “Standard Thicknesses, Weights, and Tolerances of Sheet Metal” (1931)

Secondary sources (cross-checks)

• Wikipedia, “American wire gauge” (AWG = Brown & Sharpe; cites ASTM B258)
• Metal Supermarkets, “Sheet Metal Gauge Chart”
• CustomPartNet, “Sheet Metal Gauge Size Chart”
• RMFG, “Stainless Steel Gauge Thickness”

Data last reviewed: October 2026.