Sheet Metal Gauge to Thickness Chart

Mild Steel Gauge Chart

Standard sheet steel gauges follow the Manufacturers Standard Gauge (MSG). Use these values for structural fab, auto body, and general fabrication work.

Common gauges in fabrication shops run from 10 to 22. Heavy structural work typically uses 10–14 gauge. HVAC ductwork runs 22–26 gauge. Auto body panels are typically 18–20 gauge.

Galvanized Steel Gauge Chart

Galvanized steel uses the same gauge system as mild steel but adds a zinc coating that increases the total thickness slightly. The values below reflect the base metal plus coating.

Galvanized is the standard for HVAC ductwork and outdoor enclosures. When cutting or welding galvanized, work in a ventilated area — the zinc coating releases toxic fumes when heated.

Stainless Steel Gauge Chart

Stainless steel follows the same Manufacturers Standard Gauge as mild steel but is measured differently in practice — many suppliers list stainless by decimal thickness rather than gauge. The values below are widely accepted industry standards.

Stainless is harder and springier than mild steel. When bending stainless, increase your inside radius and expect more springback — typically 10–20% more than mild steel at the same gauge.

Aluminum Gauge Chart

Aluminum uses the Brown & Sharpe (American Wire Gauge / AWG) system, which is completely different from the steel gauge system. Do not mix them up — a 14-gauge aluminum sheet is much thinner than 14-gauge steel.

Aluminum is measured on a different scale entirely. Always confirm with your supplier whether they mean steel gauge or aluminum gauge — the difference can be significant.

Common aluminum sheet for fab work runs 14–20 gauge (approximately 0.040–0.064 inches), sometimes called "0.040 sheet" or "0.063 sheet" in the trade rather than by gauge number.

How to Read a Gauge Number

Gauge numbers originated with wire drawing — each pass through a die reduced the wire diameter by a step, and more passes meant a higher number and thinner wire. Sheet metal adopted the same convention. The gauge system is not linear — the thickness difference between consecutive gauges is not constant.

This is why fabricators increasingly prefer to spec sheet metal by decimal thickness rather than gauge number, especially in precision work. Always verify with your material supplier before ordering.

Gauge vs Decimal — Which Should You Use?

In a fabrication shop, gauge numbers are convenient shorthand everyone understands. On a drawing or purchase order, decimal thickness is always more precise. If you're calculating bend allowance, flat pattern length, or cut settings for a plasma cutter, always convert to decimal first — your calculator needs a real number, not a gauge.

Run your numbers with our Metal Gauge to Thickness Converter, Sheet Metal Bend Allowance Calculator, Press Brake Tonnage Calculator, Bend Radius Calculator, and Plasma Cutting Calculator once you have the thickness dialed in.

After you convert gauge to thickness, flat-pattern method matters: Bend Allowance vs Bend Deduction — Which to Use. If formed parts still miss print, diagnose with Sheet Metal Bending Troubleshooting.