Sheet Metal Gauge Chart: Thickness Guide for Steel, Aluminum & More

Gauge numbers run in the opposite direction from thickness: a lower number generally means thicker sheet. For example, 14 gauge carbon steel is approximately 0.0747 in (1.897 mm), while 16 gauge is approximately 0.0598 in (1.519 mm). Therefore, 14 gauge is thicker.

The complication is that gauge is not one universal scale. Standard steel, galvanized steel, stainless steel, aluminum, brass, and copper may use different industry tables. Coatings, temper, product form, and supplier conventions can also change the nominal value. A “20 gauge” designation should never be transferred from one material to another without checking the relevant chart.

The gauge system developed from historical wire-drawing and metalworking practices. Manufacturers used numbered references to describe material sizes before modern precision measurement and standardized digital drawings were widely available. In many systems, repeated processing steps produced thinner material as the number increased.

Gauge terminology persists because it is familiar throughout fabrication and supply chains. It is fast for shop-floor communication and remains common in catalogues and legacy designs. Modern engineering practice combines that shorthand with decimal or metric thickness, material grade, and an acceptable tolerance.

The tables below provide common nominal reference values. Actual supplied thickness can vary with the material standard, mill tolerance, coating, temper, and supplier. When a dimension is critical, we verify the applicable standard and inspect the incoming or finished part against the drawing requirement.

Standard Steel Gauge Chart

This common carbon or mild steel reference is useful for early design comparisons. Steel gauge values are nominal; cold-rolled and hot-rolled products may be supplied to different thickness ranges and tolerances.

Galvanized Steel Gauge Chart

Galvanized sheet has a zinc coating over steel. Depending on the industry convention, a stated gauge may refer to the coated product thickness or the base steel thickness. The coating adds to the measured overall thickness and can affect forming, bend clearance, and cut-edge behavior.

These are reference values, not a substitute for the supplier’s galvanized coating designation and thickness tolerance.

Stainless Steel Gauge Chart

Stainless gauge tables are commonly applied to grades such as 304 and 316, but grade, finish, temper, and mill standard still matter. Stainless work-hardens during forming and may require different tooling or bend allowances than carbon steel at a similar nominal thickness.

Aluminum Gauge Chart

Aluminum is lighter than steel at an equivalent thickness, so designers often evaluate stiffness, span, folds, ribs, and alloy—not just gauge. Common alloys and tempers can have different forming and strength characteristics, while the gauge-to-thickness reference remains a useful starting point.

Brass and Copper Gauge Charts

Brass and copper are often specified by thickness in inches or millimeters, although gauge references remain in use. Their electrical, thermal, corrosion, and forming properties make them useful for terminals, heat-transfer components, decorative panels, shielding, and hardware.

Brass and copper gauge conventions can vary more than many steel references. For electrical or thermal parts, we confirm the alloy, temper, conductivity requirement, and exact thickness with the material supplier.

The quick rule is simple: within the same material gauge system, the smaller number is thicker. The exact comparison still depends on the material table, so we use nominal thickness values rather than relying on the gauge number alone.

Gauge selection is a design decision, not simply a lookup exercise. We review the part’s loads, geometry, environment, joining method, finish, quantity, and manufacturing process before recommending a practical material thickness.