This sheet metal thickness chart converts common gauge sizes to inches and millimeters. Gauge numbers are convenient, but they are not universal measurements: the same gauge can represent a different thickness in carbon steel, stainless steel, and aluminum. Use the tables below to specify the correct material thickness before requesting a quote.

How to Use This Sheet Metal Thickness Chart

Gauge is a historical sizing system used for sheet and wire products. The number does not directly represent inches or millimeters, and the relationship is not linear. A change from 18 gauge to 16 gauge does not equal a fixed thickness increase, and material-specific gauge systems use different nominal values.

For modern manufacturing drawings, the clearest practice is to specify the material grade and the nominal thickness in inches or millimeters. Gauge can be included as a reference, but it should not replace a numerical thickness. Actual delivered material can also vary within the mill tolerance for the applicable alloy and product specification.

Use this sheet metal thickness chart as a quick reference, then place the exact nominal thickness and material grade on the production drawing.

Mild Steel Sheet Metal Thickness Chart

The following values use the United States Standard Gauge for sheet and plate iron and steel. They are commonly applied to cold-rolled and hot-rolled carbon steel sheet.

Stainless Steel Sheet Metal Thickness Chart

Stainless steel gauge values are slightly thicker than the equivalent mild steel gauge in many common sizes. Specify the stainless grade—such as 304 or 316L—along with the nominal thickness and finish.

Aluminum Sheet Metal Thickness Chart

Aluminum commonly follows the Brown and Sharpe gauge series. Because aluminum alloys and tempers differ in formability and strength, the drawing should identify both the alloy-temper designation and the nominal thickness.

Common Sheet Metal Gauge Sizes at a Glance

The most frequently requested values from a sheet metal thickness chart are the common enclosure and bracket gauges shown below.

How to Convert Inches to Millimeters

Use the standard conversion:

Conversion does not eliminate material tolerance. A CAD model may use the nominal value while the actual sheet supplied falls within the allowable range for the relevant specification.

How to Select the Right Sheet Metal Thickness

1. Start with the load and stiffness requirement

Thickness has a strong effect on panel stiffness, vibration, dent resistance, fastener pull-through, and assembly weight. A thin panel can often be reinforced with bends, beads, flanges, ribs, or hems instead of increasing the thickness of the entire part.

2. Check the available bend radius and tooling

Thicker and higher-strength sheet usually requires a larger inside bend radius, more press-brake force, and wider tooling. Tight radii can increase the risk of cracking, marking, or dimensional variation. Include critical inside radii and bend directions in the drawing.

3. Review holes, slots, and edge distances

Features placed too close to a bend may stretch or distort. Very small holes in thick sheet can also increase tooling and cutting constraints. A design-for-manufacturing review should check hole diameter, bend relief, slot width, edge distance, and hardware installation.

4. Account for finishing

Powder coating, plating, anodizing, passivation, and brushing can affect fit, appearance, conductivity, and masking requirements. Coating buildup is not part of the base-metal gauge, so critical finished dimensions should clearly state whether they apply before or after finishing.

5. Use stock thicknesses when possible

Standard stocked material normally reduces sourcing time, scrap, and project cost. If a design can accept the nearest readily available thickness, it may quote faster than a part that requires a special mill size. See our guide to sheet metal fabrication cost for the other variables that affect pricing.

Gauge, Thickness, and Fabrication Cost

Thicker material can increase raw material cost, part weight, cutting time, bend tonnage, and shipping cost. However, choosing the thinnest possible sheet is not always economical. Insufficient stiffness can require extra brackets, welds, hardware, or secondary forming operations.

The lowest-cost solution is usually the thinnest standard stock that still satisfies strength, stiffness, forming, fastening, and service requirements. Xproto can review drawings for manufacturability and recommend practical stock options through our custom sheet metal fabrication service.

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Reference Notes

Nominal gauge values are based on established U.S. sheet-metal gauge series. Historical steel and stainless gauge references can be found in the NIST Letter Circular 24. Current aluminum product dimensions and tolerances should be checked against the applicable alloy specification and the Aluminum Association standards. Measurement procedures for steel sheet are covered by ASTM A1073/A1073M. Values in this article are for design reference and do not replace supplier certifications or project specifications.