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Sheet Metal Gauge Conversion Factors

With applications in art and architecture as well as automotives and aerospace, among others, sheet metal is a vital construction material. Workers often need to be precise in their forming and handling of the metal and it is important to know what thicknesses are available for specific purposes. Sheet metal has its own particular sizing nomenclature and conversion to more workable information is sometimes necessary.

More Is Less
- It can be confusing working with sheet metal thicknesses, which are sized as gauges. The operating principle is: The smaller the gauge, the thicker the metal. The largest thickness is a 3 gauge. To further complicate things, gauge conversion differs according to which metal is being used. They include steel (both standard and galvanized), aluminum, copper, nickel, titanium, tin and brass. The most common applications are with steel and aluminum.
Standard and Galvanized Steel
- OnlineConversions.com's conversion chart shows thicknesses for standard and galvanized steel from the maximum of 3 gauge down to 36 gauge. Thicknesses are measured out to the nearest 10,000th unit in standard sizes as well as metric. Standard steel measurements drop off approximately 0.0150 inch in standard measurement. A 3 gauge is 0.2391 inch and a 4 gauge is 0.2242, a difference of 0.0149, approximately a 6 percent change. The galvanized steel chart begins at 9 gauge.
Aluminum
- Aluminum sheet metal shows about a 9 percent change with each gauge conversion. Aluminum's chart begins at 3 gauge (0.2294 inch) and goes down to 35 gauge, or 0.0056 inch.
Other Sizes
- Any sheet metal thicker than a 3 gauge is generally called "plate" and anything thinner than 36 gauge is called "foil."

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