How is rebar size indicated?

Rebar size is indicated in half of an inch, which is a common practice in North America. In this system, the number that precedes the "bar" designates the nominal diameter of the rebar in eighths of an inch. For example, a #4 rebar has a nominal diameter of 4/8 inch, which is equivalent to 1/2 inch. This method of sizing provides a straightforward way to recognize the thickness of the rebars and ensures that contractors, engineers, and suppliers are aligned on the specifications needed for construction projects.

This system contrasts with metric sizing, which uses millimeters or centimeters, and may apply in other regions of the world. Thus, using half of an inch gives clarity and consistency in specific markets where that measurement system is the norm.