Sheet-Metal Gauge to Decimal Thickness

The mistake behind a mis-ordered sheet. Standard (uncoated) steel uses the Manufacturers' Standard Gage (MSG, fixed by the U.S. Act of Congress of March 3, 1893; thickness = weight/41.82 lb-ft2-in): 16 ga = 0.0598 in, 14 ga = 0.0747 in, 10 ga = 0.1345 in. Galvanized steel (GSG) reads a few thousandths thicker at the same gauge because the published thickness includes the zinc coating (16 ga = 0.0625 in). Aluminum, brass, and copper follow the Brown & Sharpe formula t = 0.005 x 92^((36 - n)/39), so 16 ga aluminum is 0.0508 in -- noticeably thinner than 16 ga steel. Higher gauge numbers are always thinner. Reports the thickness in inches and mm. Stainless is commonly MSG but some mills differ -- confirm against the mill cert. Public-domain reference (1893 Act / Brown & Sharpe); the material spec and a caliper govern the delivered sheet.

Steel (MSG): thickness = weight / 41.82 lb-ft2-in (table). Galvanized (GSG) = MSG + zinc coating (table). Aluminum/brass/copper (Brown & Sharpe): t = 0.005 x 92^((36 - n)/39) in. mm = in x 25.4.

The Manufacturers' Standard Gage for steel (U.S. Act of Congress, March 3, 1893) and the Brown & Sharpe (American Wire Gage) geometric formula for nonferrous sheet, by name; public domain.

MSG is a public-domain statutory gage (the 41.82 lb-ft2-in basis) and Brown & Sharpe is the same public geometric formula the awg-wire-geometry tile uses; the gauge number and material are the user's inputs.

Estimate. AHJ and licensed professional govern.

Field names used by the API: gauge, material, thickness_in, thickness_mm

• Steel MSG Manufacturers' Standard Gage table; thickness = weight/41.82 lb-ft2-in (1893 Act)U.S. Act of Congress March 3, 1893
• Galvanized GSG MSG plus the zinc coating; reads a few thousandths thicker at the same gaugegalvanized-sheet standard
• Nonferrous B&S t = 0.005 x 92^((36 - n)/39) in for aluminum/brass/copperBrown & Sharpe / AWG