Sheet Metal Gauge Chart & Converter
Gauge ↔ mm/inch conversion for steel, galvanized, stainless steel, and aluminum — with weight per m²
Sheet metal gauge is a traditional, non-linear numbering system for thickness: the higher the gauge number, the thinner the sheet. It is also material-specific — 16 gauge steel (1.52 mm) is not the same thickness as 16 gauge aluminum (1.29 mm), which is the single most common source of ordering mistakes.
This converter covers the four systems used in practice: Manufacturers’ Standard Gauge for steel sheet, the galvanized steel gauge (slightly thicker due to zinc coating), the stainless steel gauge, and the Brown & Sharpe (AWG) system used for aluminum. Enter a gauge number to get mm, inches, and weight per square meter — or enter a thickness in mm to find the nearest gauge.
The weight column uses standard densities (steel 7.85, stainless 7.9, aluminum 2.70 kg/m² per mm) — handy for quickly estimating sheet order weight together with our sheet metal weight calculator.
Frequently Asked Questions
What thickness is 16 gauge steel?
16 gauge steel sheet is 0.0598 in = 1.52 mm (Manufacturers’ Standard Gauge). In galvanized steel, 16 gauge is 0.0635 in = 1.61 mm; in stainless 0.0625 in = 1.59 mm; in aluminum 0.0508 in = 1.29 mm. Always confirm the material system when ordering.
Why do gauge numbers decrease as thickness increases?
The system descends from wire drawing: the gauge number roughly corresponded to the number of drawing operations needed. More passes = thinner wire = higher number. Sheet gauges inherited the convention.
Is there one universal gauge standard?
No — and that is the trap. Steel, galvanized, stainless, and aluminum each use a different table. A drawing that just says "18 ga" without the material system is ambiguous; the difference can exceed 20%.
Should I specify gauge or millimeters?
Modern practice (and every standard outside the US) prefers millimeters. If you must use gauge, always state the system, e.g. "16 GA MSG steel". This chart gives you the exact mm value to put on drawings.