Gauge (or gage) is a term used to describe the size of a material or the thickness of an object. The terms are often used interchangeably, and while they can mean the same thing, there are some slight differences between the two.
Gauge is typically used to refer to the thickness of a material, such as steel, aluminum, or plastic. For example, a steel plate might be offered in a variety of gauges, such as 12 gauge, 14 gauge, and 16 gauge. The lower the gauge number, the thicker the material—so 12 gauge steel is thicker than 16 gauge steel.
Gage, on the other hand, is typically used to refer to the size of a hole or a slot. The term is often used in engineering and manufacturing, and it can refer to either the size of the hole or the size of the slot that the hole fits into. For example, a bolt might be offered in a variety of sizes, such as a 1/4” gage or a 5/16” gage, which refers to the size of the hole it fits into.
In general, gauge is used to refer to the thickness of a material and gage is used to refer to the size of a hole or slot. While the terms can be used interchangeably, the slight difference in usage is important to consider when measuring or specifying the size of an object.