What the Gauge to mm Converter does
This tool turns a sheet metal gauge number into a real thickness. Pick whether the sheet is standard steel or aluminum, choose the gauge, and it gives the thickness in millimetres and inches. It is handy whenever a drawing or supplier quotes a gauge and you need the metric thickness to cut, bend or weigh the sheet.
Gauge is a lookup, not a formula, so the values come from the recognised standards: Manufacturers’ Standard Gauge for uncoated steel, the Galvanized Steel Gauge for galvanized, and Brown & Sharpe for aluminum.
How to use it
- Choose the gauge system: standard steel, galvanized steel or aluminum.
- Pick the gauge number.
- Read the thickness in millimetres, with the inch value below.
Why use it here
It is free, instant and private, with no sign-up. It keeps standard steel, galvanized and aluminum separate so you get the right thickness for your material, and it shows both millimetres and inches at once.
Tip: once you know the thickness, use the metal weight calculator to weigh the sheet, or the bend allowance and press brake tonnage calculators to plan the bends.
Frequently asked questions
- How do gauge numbers map to thickness?
- There is no single formula; gauge is a defined table. For standard (uncoated) steel this tool uses the Manufacturers' Standard Gauge, and for aluminum the Brown & Sharpe (AWG) gauge. A higher gauge number means a thinner sheet.
- What is 16 gauge in mm?
- 16 gauge standard steel is about 1.52 mm, while 16 gauge aluminum is about 1.29 mm. The gauge number is the same but the thickness differs by material, which is why you pick the system first.
- Why are steel and aluminum different at the same gauge?
- They use different gauge standards. Steel follows the weight-based Manufacturers' Standard Gauge; aluminum and other non-ferrous metals follow the Brown & Sharpe system. So 18 gauge is 1.21 mm in steel but 1.02 mm in aluminum.
- Does it cover galvanized steel?
- Yes. Galvanized uses the Galvanized Steel Gauge (GSG), which runs from gauge 8 to 32 and includes the zinc coating, so it reads slightly thicker than uncoated steel at the same number. For example 16 gauge galvanized is about 1.61 mm versus 1.52 mm for standard steel.
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Last updated: June 23, 2026