It’s confusing to many people that steel cable, rod and sheet stock are measured using a system that appears counter-intuitive. As conventional measurements increase in number, so does weight and thickness, right? In fact, not right! The thickness of metal cable, rod and sheet stock is measured in gauge, and gauge refers back to a system in which the physical properties actually decrease as the rating number increases.
It’s uncommon knowledge! Few people know why the thickness of steel diminishes as the gauge increases (ie: 16 gauge steel is thicker than 20 gauge steel). The explanation comes from the early development of a steel gauge measurement system in which the control measurement was based on a 1″ thick steel plate. The 1″ thickness of the steel was measured in diminishing fractions such as 1/14″ thick, 1/16″ thick, 1/20″ thick, and so on. The bottom number of the fraction became an easy identifier and eventually was adopted as the “gauge number.” Thus, 1/16″ became 16 gauge and 1/20″ became 20 gauge. The concept makes sense but without explanation, the converse number is often confusing. By taking the gauge number and returning it back to a fractional format, one can discover the actual nominal thickness dimension, in inches, of sheet steel.