What is the diameter of size ___ rebar?

The diameter of size 1 rebar is indeed 1 inch. Rebar, or reinforcing bar, is categorized by its numerical size, which corresponds to its nominal diameter in inches. The size numbering system for rebar starts from size 3, which is 3/8 inch in diameter. As the size number increases, the diameter increases as well. Therefore, for size 1, which is the second size in the classification, the established diameter is 1 inch.

This classification is crucial in construction and engineering, as the diameter of the rebar determines how much tensile strength it can contribute to reinforced concrete structures. The correct selection of rebar size is vital for ensuring structural integrity and compliance with engineering standards. Adjustments in size can greatly influence the load-bearing capability of a reinforced concrete element.