Sheet Metal Gauge Chart: Thickness in Inches and mm

The charts below provide a quick reference for common gauge sizes, followed by an explanation of how to read them. We also cover how sheet thickness affects cutting, bending, and mating features when making brackets, enclosures, and other fabricated parts.

How to Use a Sheet Metal Gauge Chart

Start with the material specified for your part, then use its corresponding chart. Mild steel, stainless steel, aluminum, and galvanized steel have different gauge-to-thickness values, so a gauge number alone is not enough to identify the required thickness.

If your drawing specifies a gauge, find that number in the Gauge column and read across to its thickness in Inches or mm. For example, 16 gauge mild steel corresponds to 0.0598 inches, or approximately 1.519 mm.

If you already have a thickness in inches or millimeters, look for that value in the appropriate material chart and read across to the gauge number. When your required thickness falls between listed values, keep the specified thickness rather than rounding it to the nearest gauge. Confirm the available sheet size with your fabricator and approve any thickness substitution before production.

These charts identify nominal thickness; they do not determine which thickness your part needs. For fabrication, specify the material grade and required thickness together, including a thickness tolerance where necessary.

Steel Sheet Metal Gauge Chart

This steel sheet metal gauge chart lists common nominal thicknesses for mild steel in inches and millimeters. Use the separate charts below for stainless steel and galvanized steel.

Stainless Steel Gauge Chart

This stainless steel gauge chart shows nominal thicknesses in inches and millimeters. Stainless steel uses different gauge values from mild steel, so select this chart when checking stainless sheet specifications.

Aluminum Sheet Metal Gauge Chart

Use this aluminum sheet gauge chart to look up nominal thicknesses in inches and millimeters. For example, 16 gauge aluminum is 0.0508 inches thick, compared with 0.0598 inches for 16 gauge mild steel.

Galvanized Steel Gauge Chart

Galvanized steel has its own gauge-to-thickness values. For example, 18 gauge galvanized steel is listed at 0.0516 inches, while 18 gauge mild steel is 0.0478 inches. Use the chart below when checking galvanized sheet specifications.

Sheet Metal Thickness and DFM Considerations

Once the material and thickness are specified, a sheet metal DFM review checks whether the part’s bends, cutouts, and fastening features can be produced as drawn. A thickness change may require adjustments to these features, even when the overall shape stays the same.

For a tab-and-slot connection, compare the slot width with the mating sheet thickness and required clearance. Check the cut edges after deburring, and account for coating on the mating surfaces. A joint that fits before powder coating may become too tight after finishing.

Bend geometry needs a separate review. The specified thickness, material grade, and temper affect tooling selection and the achievable inside bend radius. Holes close to the bend can distort during forming, while short flanges may not provide enough support for the selected tooling. Depending on the geometry, the solution may involve moving a hole, extending a flange, or changing the bend radius.

For a new bent part, a trial bend helps verify the calculated flat pattern. Measure the bend angle and flange dimensions, then adjust the bend settings or bend allowance before running the batch. If an alternative stock thickness is approved, repeat the relevant checks rather than assuming the original setup will produce the same dimensions.

Fastening features also depend on the available thickness. Check thread engagement before tapping directly into the sheet, and compare countersink depth with the material remaining beneath it. Where the sheet is too thin, self-clinching nuts or other suitable fasteners may provide a practical alternative, subject to their material, thickness, and installation requirements.

Mark critical formed dimensions and mating features on the drawing so they can guide both process planning and final inspection. For broader guidance on bends, hole spacing, and fastening features, see our sheet metal design guide.

From Sheet Metal Thickness to Finished Parts

Producing a sheet metal part involves more than cutting the outline from the specified thickness. An enclosure may need bent flanges, welded corners, threaded mounting points, and a coated exterior. Each operation must follow the drawing so that the finished cover fits, the mounting holes align, and the required internal space remains available.

At ZH Precision, we provide sheet metal fabrication for brackets, enclosures, panels, chassis, and covers. Our capabilities include laser cutting, CNC bending, welding, and secondary machining, with surface finishing options selected for the material and application. We review the material grade, thickness, bend geometry, and critical features to plan the production sequence.

Inspection follows the requirements of the completed part. For a bracket, this may include the bend angle and mounting-hole positions; for an enclosure, the overall dimensions and cover fit. Where a drawing requires a machined hole or mounting surface, we incorporate the necessary secondary operation and dimensional check.

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