Sheet Metal Gauge & Thickness Chart

Standard sheet steel gauge (manufacturer standard gauge, MSG) numbers and their thickness, with a common use. Gauge is a traditional scale where lower numbers are thicker; steel, galvanized, aluminum, and stainless each use different scales, so always confirm and order by thickness in millimetres, not by gauge number alone.

How gauge sizing works

A weight-based scale that runs backwards

The gauge system predates modern precision rolling and was originally weight-based: a gauge number corresponded to a weight of sheet per area, which translated to an approximate thickness for a given metal. The numbering runs backwards, so a smaller gauge number means thicker material. Under the manufacturer standard gauge for carbon steel, gauge 4 is about 5.69mm, gauge 10 is about 3.42mm, gauge 16 is about 1.52mm, and gauge 26 is about 0.46mm. The chart lists the standard steel (MSG) values from gauge 4 down to gauge 26, which covers the common fabrication range from heavy plate to thin sheet.

Why mm beats gauge

Gauge is ambiguous because the scale changes with the metal. A 16-gauge carbon steel sheet is 1.52mm, but 16-gauge aluminum and 16-gauge stainless are different thicknesses again, and galvanized steel has its own slight variation. A drawing that calls out only 16 gauge leaves the shop to guess which scale applies, and a wrong guess produces a part at the wrong thickness and stiffness. Specifying the thickness in millimetres (or inches) removes that ambiguity, lets the shop order the correct stock regardless of its working scale, and avoids the larger unit-mismatch risk where a file without explicit units is read at the wrong scale. State the thickness in mm on the drawing and treat the gauge number as a secondary reference only.

Gauge to typical use

Gauge bands by duty

Each gauge band suits a class of work. Heavy gauges (4 to 7, around 4.5mm and up) behave like plate and suit structural baseplates, heavy brackets, and weldments. Mid gauges (10 to 14, roughly 1.9 to 3.4mm) cover general fabrication, structural brackets, and load-carrying enclosures. The 16 to 18 gauge band (1.2 to 1.5mm) is the common enclosure and panel range, light enough to handle and stiff enough to hold shape. Lighter gauges (20 to 22, 0.76 to 0.91mm) suit covers, ducts, and light shrouds, while 24 to 26 gauge (0.46 to 0.61mm) is the thin end, used for light covers and shims and harder to weld cleanly. Picking the gauge by the duty, then converting to mm, is faster than scanning every sheet option.

A worked example shows the method. A wall-mounted electrical enclosure that must support its own weight and a door might start at 16 gauge (1.52mm) for the body, drop to 18 gauge (1.21mm) for a removable cover, and step up to 14 gauge (1.90mm) for the mounting back plate that carries the load. Each choice follows the duty, and each is written on the drawing in mm so the shop orders the right stock no matter which gauge scale it uses.

Gauge and the cutting or bending process

How thickness affects cutting and bending

Thickness drives which processes run well. Fiber laser cutting handles thin to medium sheet cleanly but loses edge quality and needs more power as stock thickens past about 12mm; waterjet takes thick plate at the cost of a wider kerf; plasma cuts thick plate at looser tolerance. For bending, thicker stock (lower gauge) needs a larger minimum bend radius, often expressed as a multiple of thickness such as 1T to 2T, and harder tempers crack more readily at tight radii. A 16-gauge enclosure wall bends readily at a small radius, while a 10-gauge bracket needs a larger die and more force. Plan the gauge together with the cut and bend operations, because a thickness that suits one may force a secondary process in another.

Limitations

The chart lists standard manufacturer standard gauge values for carbon steel sheet; galvanized, aluminum, and stainless use their own scales, so the mm column is the authoritative value and the gauge number is a rough cross-reference. Real delivered thickness can sit at either end of the mill tolerance band for the gauge, and coated steels add a zinc layer on top of the base thickness. For a load-critical or fit-critical part, confirm the actual thickness on the material test report for the specific lot rather than relying on the nominal gauge value.