Sheet Metal Gauge Chart: Steel, Stainless & Aluminum

Gauge needs a material: use a dimensional thickness

A sheet metal gauge number is not a universal thickness. The same number maps to different nominal thicknesses for steel, stainless steel and aluminum. For an order, specify material, thickness in inches or millimeters, and the applicable tolerance. Use the gauge number as a reference alongside them.

These selected reference values follow eMachineShop’s published chart. Millimeters are calculated as inches × 25.4 and rounded to three decimals. The table is a nominal reference, not a stock list or thickness tolerance; it does not cover galvanized sheet or wire gauge systems.

Worked example: why “16 gauge” is incomplete

In the table, 16 gauge steel is 0.0598 in, while 16 gauge aluminum is 0.0508 in. The difference is 0.0090 in, or 0.2286 mm. For a cover sliding into a channel, that difference can matter even before manufacturing variation and finishing are considered.

If someone changes the material from steel to aluminum and leaves only “16 gauge” on the drawing, they have changed both material and nominal thickness. To preserve a dimensional design requirement, state that requirement explicitly and evaluate the offered stock. Do not assume an identical gauge preserves the original fit.

Our recommendation is to approve an actual material-and-thickness line before authorizing the cut. If the supplier offers 1.5 mm stock against the 16 gauge steel reference, the nominal difference is 0.01892 mm. Whether that is acceptable depends on your limits and the stock tolerance, not on whether the numbers look close.

Write a thickness note that survives quotation

A useful drawing note names the alloy, condition, nominal thickness, units and the tolerance or material specification governing it. If an alternative is acceptable, identify the allowed limits. “Use the nearest stock” leaves the deciding criterion with the supplier.

For a bent part, send the folded model and finished dimensions as well as the flat profile. A thickness change can require the manufacturing flat pattern to be reviewed; copying the old DXF is not a complete approval. The sheet metal service checklist separates those inputs.

Check the delivered part against the right reference

Agree whether the thickness requirement refers to the base material or the finished part. When a coating is present, a measurement across the finished surfaces includes that coating. Keep the receiving inspection method consistent with the approved requirement.

For a first sample, record the material designation, measured thickness, measurement locations and drawing revision. If the part is bent, also check the assembly-critical dimensions after forming. A correct nominal sheet thickness cannot by itself prove that a finished enclosure fits.

Reference tables help resolve an early question. The released drawing and agreed material specification provide the acceptance basis for the order. Send them with your laser-cut profile when requesting a quotation.