Sheet Metal Gauge to mm Chart
Gauge is not a universal unit: carbon steel, galvanized steel and aluminium each use a different gauge system, so one number means three thicknesses. This chart converts the common sheet gauges to millimetres for steel and aluminium, and explains why we ask drawings to be dimensioned in mm instead.
Specify thickness in mm, not gauge
Gauge numbers come from wire-drawing history, not from metal thickness. Three systems are still in circulation — carbon steel (MSG), galvanized steel (a heavier gauge for the same number, because the coating counts) and aluminium (Brown & Sharpe) — so "16 gauge" can mean 1.52 mm, 1.61 mm or 1.29 mm depending on who is reading it. Every drawing we check gets read back in millimetres before quoting, and if a customer specifies gauge we confirm the mm equivalent in writing.
Carbon steel sheet — Manufacturers' Standard Gauge
The gauge most fabrication drawings mean when they say "16 gauge steel". Hot-dip galvanized sheet in the same gauge number runs slightly thicker because the zinc coating is included in the gauge definition.
Aluminium sheet — Brown & Sharpe
Aluminium keeps its own gauge system. A "16 gauge aluminium" part is 1.29 mm — nearly 15% thinner than the same gauge in steel, which is enough to change both the bend force and the part's stiffness.
The number that actually matters
Tolerances, bend radii and tooling are all specified in millimetres, so a gauge callout is translated before anything is cut. Put the mm value on the drawing and gauge stops being a risk. If your drawing only has gauge, send it over — we confirm the conversion in writing before quoting.
Questions about gauge and thickness
Manufacturers' Standard Gauge for carbon steel sheet; Brown & Sharpe for aluminium.
Why does 16 gauge mean different thicknesses?
Because "gauge" is a historical wire-drawing scale, and each material family kept its own. Carbon steel uses the Manufacturers' Standard Gauge, aluminium uses Brown & Sharpe, and galvanized steel is defined heavier because the coating counts toward the gauge. One number, three thicknesses.
What gauge is 2 mm sheet steel?
2 mm falls between 14 gauge (1.90 mm) and 13 gauge (2.28 mm) — there is no exact gauge for it, which is exactly why we ask for millimetres. Most fabrication outside North America works directly in mm.
Can you work to a gauge spec if our drawings already use it?
Yes. Send the drawing and we confirm the mm equivalent we will hold in writing before quoting, so the spec is unambiguous on both sides.
Keep going
Calculators — enter dimensions, get a number
Sheet Metal Weight CalculatorWeight per piece and per batch from L × W × t, with real alloy densities.Bend Allowance CalculatorThe neutral-axis length through a bend, from thickness, radius, angle and K-factor.Sheet Metal Cost CalculatorWhere a part’s cost actually sits — material, cutting, forming, finishing and setup.Press Brake Tonnage CalculatorBending force in kN and tons from thickness, material and bend length, with a 20% margin.K-Factor Calculator (Reverse)Reverse a K-factor from a real bend: outside dimensions and flat length in, K out.Hole-to-Bend Distance CalculatorMinimum hole-to-bend and hole-to-edge clearances from thickness and inside radius.Charts and checklists — read, print, work through
Sheet Metal DFM ChecklistThe 24 checks we run on a drawing before we quote it, grouped and explained.Sheet Metal RFQ ChecklistThe 12 items that make an RFQ quotable in one round, with the reason each matters.Sheet Metal Supplier Audit Checklist13 remote-verifiable checks for a sheet metal supplier, in four passes.Send the drawing — we read it back in mm
Upload a drawing in any unit system. Our engineers confirm every thickness in millimetres, flag anything ambiguous, and quote from the unambiguous version.
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