Steel Sheet & Plate Thickness Chart (US Standard Gauge)
The US Standard Gauge for iron and steel sheet and plate — the gauge number, its inch fraction, decimal inch and millimetre equivalent.
| US gauge | Fraction (in) | Decimal (in) | Millimetres |
|---|
Standard: 15 U.S. Code § 206 (US Standard Gauge) · Data checked: 2026-10-14
Frequently asked questions
Why does the same gauge number mean a different thickness in different metals?
Because the US Standard Gauge was fixed for iron and steel sheet and plate specifically. Manufacturers of galvanised sheet, aluminium and stainless publish their own gauge tables, and they do not agree with each other. A drawing that says '16 gauge' without saying in what material is ambiguous.
How much does galvanising add to the thickness?
Typically 0.02 to 0.1 mm depending on the coating class, which is enough to matter at finer gauges. Galvanised sheet is usually quoted as the base steel thickness plus a coating designation, so check which figure a supplier is quoting.
Is the US Standard Gauge legally defined?
Yes, it was fixed by 15 U.S. Code section 206 for determining duties and taxes on imported iron and steel. That is why the table on this site is unusual in being traceable to a statute rather than to a trade convention.
Should I specify gauge or thickness?
Thickness in millimetres or inches, every time, if the part matters. Gauge numbers depend on the standard used and on the material, so they are a shorthand for conversation, not a specification.