Sheet Metal Gauge & Thickness Converter
Translate between sheet-metal gauge numbers and real thickness in millimetres and inches — using the correct table for steel, galvanized, stainless, or aluminium.
Gauge is a label, not a measurement
A gauge number is a historical shorthand for sheet thickness that grew out of how metal was once weighed and drawn, so the same number maps to a different thickness in steel, galvanized steel, stainless, and aluminium. That’s why a drawing should always state both the gauge and the material — and why this converter keeps a separate table for each.
Know the thickness you’re working with and the Bend Allowance Calculator can size the flat blank before forming, while the Metal Weight Calculator turns the sheet size into a weight.
Frequently Asked Questions
Why does the same gauge mean different thicknesses for different metals?
Gauge is an old system tied to material and weight, not a fixed measurement, so each material has its own table. 16-gauge uncoated steel is about 1.52 mm, but 16-gauge galvanized steel is thicker (about 1.61 mm) because of the zinc coating, 16-gauge stainless is about 1.59 mm, and 16-gauge aluminium — which uses the Brown & Sharpe / AWG system — is only about 1.29 mm. Always convert using the table for the material you actually have.
Which gauge tables does this converter use?
Standard steel uses the Manufacturers' Standard Gauge for uncoated sheet; galvanized steel uses the galvanized table that includes the coating; stainless steel and aluminium each use their own standard tables. Pick the material first and the converter applies the matching table in both directions.
Can it go from a thickness back to a gauge?
Yes. Switch to 'thickness → nearest gauge', enter a thickness in millimetres or inches, and it returns the closest gauge in that material's table along with how far off it is. Because real gauges are discrete steps, your measured thickness usually lands between two of them, so it reports the nearest.
Should I trust the gauge or measure the metal?
Measure it. Gauge tables are nominal and standards vary between mills and countries, and coatings and tolerances shift the real number. For machining, bending, or fit-up, confirm the actual thickness with a caliper or micrometer and treat the gauge as a label, not a guarantee.
Educational reference from standard gauge tables. Standards vary — confirm actual thickness with a caliper before machining or bending.