Sheet Metal Gauge Chart: Thickness, Weight and the Machine You Need

If you work with sheet metal, you are probably already familiar with terms such as 14 gauge, 16 gauge, 18 gauge, and 20 gauge. Gauge is widely used to specify sheet metal thickness, particularly in North American metal fabrication and manufacturing.

But there is one important detail: a gauge number does not represent a universal thickness across all metals. The thickness associated with a particular gauge can vary depending on the material. For example, 16 gauge carbon steel, stainless steel, and aluminum do not necessarily have the same thickness in millimeters.

This becomes especially important when you are ordering material, checking a technical drawing, comparing suppliers, or selecting a machine for cutting and bending.

In this sheet metal gauge chart, we will compare steel, stainless steel, and aluminum gauge thicknesses in millimeters and inches. We will also explain how sheet thickness relates to press brake tonnage and shearing machine capacity, so you can move from simply identifying the material thickness to choosing the right processing equipment.

Illustration only. The small gauge/weight table within this image is not consistent with the conversion tables below and must not be used for ordering material or sizing a machine.

What is sheet gauge?

Sheet metal gauge is a numbering convention for thickness. In the common charts below, a higher gauge number means a thinner sheet. The convention depends on the metal and gauge system; it is not a universal measurement in millimeters.

Gauge numbers are historical size designations, not a count of the rolling passes used to manufacture a sheet. Specify the material, gauge convention and nominal thickness together when ordering.

Another key rule must be noted: gauge standards are material-specific. The same 16Ga size has different thickness data for carbon steel, stainless steel, and aluminum. This is the core reason for processing errors and drawing recognition deviations in daily work, and also the key basis for accurate equipment tonnage matching. For example:

• 12 Gauge → 2.66 mm steel

• 16 Gauge → 1.52 mm steel

• 20 Gauge → 0.91 mm steel

Sheet Metal Gauge to Millimeters and Inches

The steel table uses common uncoated sheet-steel gauge values; the aluminum table uses the Brown & Sharpe convention. The stainless table follows commonly published supplier values. Galvanized steel has a separate chart and is not covered here. Values are nominal, with millimeters rounded to two decimals; confirm the ordered thickness and permitted tolerance with the supplier.

How to Use the Gauge Tables

For example, 16-gauge sheet is nominally 1.52 mm for uncoated steel, 1.59 mm for stainless steel and 1.29 mm for aluminum in these charts. State both the material and thickness on the purchase order.

Stainless Steel Gauge to mm & inch Chart

Aluminum Gauge to mm & inch Chart

Estimating Sheet Weight

Sheet mass (kg) = length (m) × width (m) × thickness (mm) × density (kg/m³) / 1000.

For a preliminary carbon-steel estimate, density 7850 kg/m³ gives 7.85 × thickness (mm) kg/m². A 2 m × 1 m sheet at 1.90 mm therefore weighs about 29.8 kg. Use the actual alloy density and measured thickness for a more accurate estimate; allow separately for coatings, pallets and packaging.

From Sheet Thickness to Machine Capacity

Sheet thickness is only one factor when selecting a press brake or shearing machine. Capacity also depends on material strength, bending or cutting length and the process requirements, as shown below.

What Machine Capacity Do You Need?

For a Press Brake

If you are converting gauge thickness for a press brake application, you also need to consider material strength, bending length, die opening and bend angle. Use our Press Brake Tonnage Calculator to estimate the required tonnage.

Example: Choosing a Press Brake for 14-Gauge Steel

A customer needs to bend 14-gauge mild steel, approximately 1.9 mm thick, over a bending length of 2000 mm.

The 1.9 mm thickness alone is not enough to determine the press brake size. The required tonnage also depends on the material strength, bending length and V-die opening.

For illustration, with tensile strength 450 MPa and a 16 mm V-opening, air bending 1.90 mm material over 2 m gives about 293 kN, or 29.9 metric ton-force. That is a force estimate, not a machine selection. Check the required working length, tooling limits, bend geometry and manufacturer’s allowance before comparing models.

Key point: Gauge tells you the sheet thickness; the bending length and material determine how much machine capacity you need.

For a Shearing Machine

For sheet cutting, the required shear capacity depends mainly on material thickness, material strength and cutting length.

Example: Choosing a Shearing Machine for 12-Gauge Steel

A customer needs to cut 12-gauge mild steel sheets, approximately 2.66 mm thick, with a maximum cutting length of 3000 mm.

In this case, the key parameters are material thickness, material strength and cutting length.

A shear nominally rated for 4 mm mild steel over 3000 mm may be a candidate, but only if its stated reference material strength covers the actual sheet. A “4 × 3000 mm” designation must not be read as the same capacity for stainless or high-strength steel. Check the supplier’s material-specific capacity table.

Key point: For a shearing machine, gauge determines the approximate material thickness, while the cutting length determines the required machine width.

Before You Choose a Machine

A sheet metal gauge chart is a useful starting point when a drawing or specification uses gauge numbers instead of millimeters. However, gauge should not be used alone when planning a fabrication process.

First, convert the gauge number into the actual thickness in millimeters and confirm the material type. Then consider the sheet size, bending length or cutting length, material strength, and required production process.

For example, knowing that 14-gauge mild steel is approximately 1.9 mm thick tells you the material thickness—but it does not tell you which press brake or shearing machine you need. Machine capacity must be determined from the complete processing requirements.

In short: Gauge tells you how thick the sheet is. Your material and processing requirements tell you what machine you need.

If you already know your sheet thickness and bending requirements, use our Press Brake Tonnage Calculator to estimate the required capacity, or explore our CNC Press Brake and Hydraulic Shearing Machine solutions for your application.

Enter the verified material thickness and bend dimensions in the press brake tonnage calculator rather than entering a gauge number as millimeters.

For cutting equipment selection, compare guillotine and swing beam shearing machines against the actual material and cutting length.

Common Questions

Is galvanized steel the same thickness as uncoated steel at the same gauge?

Not necessarily. Use a galvanized-steel chart and the supplier’s coating and base-metal specification; do not use the uncoated table without checking.

Should I select a machine from gauge alone?

No. Convert gauge to nominal thickness, verify the actual material and tolerance, then evaluate strength, bend or cut length and process requirements.